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Beware of Dry Conditions When Soil Sampling and Interpreting Test Results

ICM News - Wed, 10/05/2022 - 13:37

October began dry across most of Iowa except for some areas in southern and southeast Iowa. These conditions are allowing for rapid harvest progress. The outlook for the rest of the month calls for lower than normal rainfall. Below normal rainfall since August until the soil sampling time may result in lower than expected soil test results for phosphorus (P), potassium (K), and pH. Therefore, farmers and crop consultants should interpret those soil test results with caution.

Caption: Soil testing dry soils, like those experienced in Fall of 2022, requires extra caution when interpreting results.

Additionally, soil sampling with dry soils needs to be done carefully to avoid losing loose topsoil from the probe, which may result in even lower P and K values. This will especially be the case when sampling no-till fields or pastures because of the usual nutrient accumulation in the top few inches of soil. The correct 6-inch sampling depth also may be compromised with highly compacted or loose soil.

Effects on soil P and K

An article written in the Fall of 2020 discusses in detail how to interpret soil test results for P, K, pH, and buffer pH with late summer and early fall drought. The following are quick reminders:

With lower yield than expected, P and K removal with harvest will be lower than normal, and in theory would result in higher than expected soil P and K levels. However, a couple of processes may counteract this possible increase and most likely will result in lower soil-test P and K results than expected.

  • Below normal rainfall from the time of physiological plant maturity until the time of soil sampling results in much less K recycling to the soil than normal, and consequently lower soil-test K levels than with normal fall rainfall.
  • While a small soil-test P reduction is possible, it is also less likely.  
  • Scarce or no rainfall since early September slows down the normal reactions between soil nutrient pools, which often results in lower soil-test P and K levels. Plants are like pumps taking up P and K from the soil, but the uptake decreases sharply a couple of weeks before the crop reaches physiological maturity. Normal rainfall allows for the replenishment of the available nutrient pools from the less available pools.
Effects on soil and buffer pH

Soil pH values likely will be less than normal (more acidic) with drought, with differences ranging from 0.1 to 0.4 pH units being common. This is because small concentrations of soluble salts normally present in the soil solution are not leached to deeper layers by rainfall, which results in higher hydrogen ion concentration and greater acidity in the topsoil. On the other hand, drought has little effect on the soil buffer pH, which is used to estimate the lime requirement. Therefore, the main issue is to remember the pH may be lower than it would be if you wait to sample until after a rainfall to decide if liming is needed, but the amount of lime to apply will not be affected.

Effects on soil profile and cornstalk nitrate

Less rainfall than normal during late summer and early fall often results in higher nitrate concentrations in the soil profile and in higher values with the end-of-season cornstalk nitrate test. A Fall 2021 article discusses these issues in detail and provides advice about what to do. Even with higher nitrate levels than normal, a large reduction of the fall or early spring N rate for corn is not recommended because spring rainfall and soil nitrate mineralization/immobilization reactions frequently override fall conditions.

Consider current crop and fertilizer prices

The P and K fertilizer availability and supply this Fall are much better than last year, but the prices remain almost as high. Therefore, carefully consider how much money you are likely to make from this fall’s harvested crops, current fertilizer prices, and the difficult-to-guess crop prices for next Fall, when you plan fertilization for this Fall. This article, written in the Fall of 2021, provides useful advice about how to consider high P and K fertilizer prices.

In summary, considerations for Fall soil test interpretations with drought:

1. Delay soil sampling until about a week of meaningful rainfall occurs because it will result in a better sample and more reliable soil-test results. It is not possible to precisely say how much rainfall is helpful, but it should be sufficient to wet the soil throughout the sampling depth (usually six inches).

2. If you take the soil samples during dry conditions:

- Be careful with sampling depth control and that you collect the complete soil core.

- Remember soil K test results may be lower than they would be with normal conditions, but soil test P results probably will be less affected.

- Soil pH may be lower than in normal conditions, which may encourage you to apply lime when is not needed, but the amount of lime to apply based on buffer pH will not be much affected.

3. Do not reduce the planned N rate for corn because of higher-than-normal soil profile or end-of-season cornstalk nitrate values in the fall, unless you are ready to apply additional N in the spring or at sidedress time if spring weather suggest significant soil nitrate losses.

For additional information about P, K, and pH/lime management visit the Iowa State University Extension Soil Fertility website at http://www.agronext.iastate.edu/soilfertility/.

Crops: CornMinor cropsSoybeanCategory: SoilsSoil FertilitySoil ManagementTags: soil samplingsoildry soil

Keep an Eye Out For This Weed

ICM News - Wed, 10/05/2022 - 09:23

While Iowa weed communities change constantly, it is rare that a species new to the region is discovered. Asian copperleaf (Acalypha australis) was first discovered in Iowa in 2016 in a corn field near Cedar Falls. Prior to this discovery, the only documented infestation in North America was within New York City. The plant was recently found in a soybean field in Grundy County, nearly 30 miles from the original infestation (Figure 1). In both fields, several dense patches of the weed were present throughout the field, indicating the weed was in the field for several years before being identified.

Figure 1. A farmer in Grundy County noted a dense population of Asian copperleaf at soybean harvest. (Photo courtesy of Bob Hartzler)

The plant is native to China, Australia, Japan and other countries in the region. It is unknown how the plant was introduced to Iowa, but it is likely the two reported infestations are related. The plant is a threat to row crops in its native range. Two sources note this species has populations resistant to HG 9 (glyphosate) and HG 14 (PPO inhibiting) herbicides in its native range. A USDA Risk Analysis completed in 2012 stated that the species did not show ‘any strong invasive or weediness characters’, but because of a high level of uncertainty the plant was classified as “High Risk” in 57% of the simulations.


Asian copperleaf is in the spurge family but lacks milky sap common in many spurges. It is an erect plant that can reach heights of 2-3 ft., but most plants found in Iowa were less than 18” in height. Leaves are 2-3” long, lanceolate with serrated (finely toothed) edges. The distinguishing characteristic of Asian copperleaf are the bracts located beneath the flowers. The bracts are circular to heart-shaped with a dentate margin (Figure 2). Virginia copperleaf and three-seeded mercury, two other Acalypha species present in Iowa with a similar growth habit, have deeply-lobed bracts (Figure 3). It is unlikely that anyone could confidently differentiate between these species prior to flowering. Asian copperleaf seems to emerge late in the season and remains under the crop canopy throughout the growing season.

Figure 2. Asian copperleaf has circular to heart-shaped bracts beneath flowers.


Figure 3. Deeply-lobed bract like that from Virginia copperleaf and three-seeded mercury (left) compared to a heart-shaped bract from Asian copperleaf (right).

Requested action. The Iowa Department of Agriculture and Land Stewardship and Iowa State University are interested in determining how widespread the weed is across the state. By determining how much area is infested with this weed, we can better estimate the risk it poses to Iowa crop production. Asian copperleaf was detected in both fields during crop harvest. Thus, we are requesting that farmers and others in the agricultural industry keep an eye for this plant as fields are harvested. If you detect the plant, please contact the Iowa Department of Agriculture and Land Stewardship at 515-725-1470.

Crop: SoybeanCategory: WeedsTags: Asian copperleafsoybean weedsWeeds

Regional Update: Harvest Edition October 2022

ICM Blog - Tue, 10/04/2022 - 16:11

With harvest underway across the state, check out what ISU Extension and Outreach field agronomists are hearing regarding how harvest is going, how are the crops yielding, and what types of end-of-the season issues they are receiving questions on.  


Northwest Iowa

Gentry Sorenson (Region 2): “Corn and Soybean harvest is underway in NW Iowa. Most farmers are focusing on soybeans harvest currently as conditions have been good to make significant harvest progress. I have heard a variety of yield results across the area, with good yields reported in areas that had adequate rainfall.  Areas that have had drought stress to severe drought stress are reporting impacted soybean yields from the drought.  I have had phone calls related to green stem syndrome soybeans in the counties that I serve as well as purple soybean stems in soybeans.  After evaluation of a few corn fields before harvest, I noted tar spot and northern corn leaf blight were found in several fields.  A map of the counties in Iowa that tar spot was detected can be found here.  As seed decisions are made for the 2023 growing season it is important to understand the disease ratings of corn hybrids and soybean varieties going into the growing season to make important agronomic decisions next growing season.  Phone calls consisted of questions about corn and soybean disease and green stem syndrome soybeans.”

North Central Iowa

Angie Rieck-Hinz (Region 3): “Harvest is in full swing in NC Iowa. The crop report as of Monday indicated 8% of the corn was harvested and 27% of the beans are harvested.  In some areas farmers report they are finished harvesting beans, some have just started beans after taking out some corn, some are mostly done with corn, and some are just starting corn. It is a mixed bag, just like the entire growing season. Yields are also highly variable and dependent on rainfall across the area. Harvest conditions have been ideal thus far, with lower humidity and continued dry down of crops. While areas continue to show up on the drought monitor, the drier areas for September included areas like Northwood, Mason City and Hampton which all averaged over 2.25 inches below normal for September rainfall- a possible indication that drought conditions are continuing to creep eastward.”

Soybean field ready for harvest in NC Iowa. Photo courtesy of Angie Rieck-Hinz.

Northeast Iowa

Josh Michel (Region 5): “Over the past two weeks, only a few areas in NE Iowa have received up to 0.10 inch of rainfall. On September 28th, we also saw temperature lows down to 29°F in some isolated areas; resulting in a killing frost for any corn and soybean fields that were not fully mature yet. Corn grain harvest has just started throughout the region as the last fields being harvested for silage are finishing up. With less than 10 percent of fields combined so far, yield reports have been widely variable. An estimated 80 percent of soybean fields have dropped their leaves. Less than 10 percent of soybean fields have been harvested so far as well. As expected, yield reports have also been widely variable. I’d expect corn and soybean harvest to come into full swing this week as we have favorable weather conditions. The cold temperatures also prompted several questions pertaining to feeding forages that may have received cold injuries. Thankfully, a killing frost for alfalfa is considered to be around 24°F for at least a few hours. While we didn’t receive a killing frost, there could be some isolated areas with light frost damage. This was a big sigh of relief as many of our alfalfa fields will need some addition growth before winter. Pastures continue to look good, although some are starting to look a little dry. Most of my field calls over the past week have consisted of finishing up silage harvest, forage management and cold-injury concerns, and weed management in pastures.”

Rainfall totals across NE Iowa for the last two weeks. Source: NOAA.

Southwest Iowa:

Aaron Saeugling (Region 10): “Harvest is well underway in SW Iowa. Corn harvest began with silage and high moisture corn being harvested first with variable yields from lows in the 50 bushel/acre range in dry areas to better rainfall areas being closer to the 200 bushel/acre range. Some standability issues have been observed in corn and those fields will be targeted for early harvest. Corn disease seems to be more prevalent than initially thought with grey leaf spot and tar spot being the most prominent. Soybean harvest really got a jump start over the weekend, and I expect with good weather this week many of the soybeans will be harvested. Getting reports of green stems and dry soybeans being common. Yields are average for most farmers, and will be mid 50’s to low 60’s. Pastures are in poor to very poor conditions depending on the September rainfall totals. I expect a large volume of corn stalks to be baled for winter feed. Be careful when considering fall tillage due to poor subsoil conditions and the lack of precipitation potential in the long-term forecast.”

East Central, Southeast, and South-Central Iowa:

Rebecca Vittetoe (Region 8): “Combines first started rolling about two weeks ago in part of EC Iowa, but they really started rolling over the last week. I’d estimate that about 15-20% of the soybeans have been harvested across the counties I cover, and about 15% of corn has been harvested. Based on the yield reports I’ve heard, yields are variable. One comment I’ve been hearing a lot about soybeans this year is the number of leaves, especially green leaves, still on the plants even though the grain moisture is ideal for harvest. On the corn side, continue to scout for stalk rots and watch stalk quality, and I’ve also had some questions asking about “the edge or border effect” in corn, especially in some of the drier areas in EC Iowa. Forages could benefit from some rain here this fall. Also, don’t forget that fall can be a great time to control some of our perennial or biennial weeds in pastures or hayfields.”

A common observation this fall: soybeans ready for harvest but still hanging onto their leaves. Photo courtesy of Rebecca Vittetoe.

Check out the map below to find your local ISU Extension field agronomist and find their contact information here!

Category: Crop ProductionTags: regional updateharvestcrop yieldsend of the seasonstalk rotsgreen stem syndromedroughtAuthor: Rebecca Vittetoe

Green Leaves Still Sticking on Soybean

ICM Blog - Mon, 10/03/2022 - 13:58

Fall is in the air and harvest is starting up across Iowa. It has been noted soybean are holding onto their leaves. This green bean effect is more often thought of as green stems, however, this year there are more leaves and petioles staying green and attached to the main stem. Take note this occurrence may mean that soybean grain is drier than expected based on plant appearance. This green bean effect can be caused by both biotic (stink bugs, thrips, viruses, etc.) and abiotic (weather, late planting, fungicides, etc.).

Management to avoid green bean syndrome is difficult in-season because of variety of causes. At harvest, the best solution to green bean syndrome is to harvest fields when the soybean seeds are at the proper moisture content. Make sure the sickle bar on the combine is sharp and well-maintained. Slower harvest speeds will be needed to account for more soybean biomass coming through the combine.

Soybean at harvestable grain moisture with green (and yellow) leaves still attached. (photo credit: Rebecca Vittetoe)

Category: Crop ProductionTags: green stem disorder; green stem syndromeAuthor: Mark LichtCrop(s): Soybean

Fall Burndown Treatments for Winter Annual Weeds

ICM News - Fri, 09/30/2022 - 15:16

Recent rainfalls are likely to result in the establishment of winter annual weeds. Many fields may have dense stands of these weeds going into winter (Figure 1). It is often difficult to achieve timely burndown of these species in the spring, so farmers with persistent problems should consider making a fall burndown application to control winter annuals.

Figure 1. Henbit seedlings under a corn canopy on September 23, 2022 near Ames, IA.

Fall burndown applications may be beneficial in fields with a history of problems with winter annuals like horseweed (marestail), field pennycress, and henbit. The advantages of fall applications include more consistent control and less weed biomass the next spring that may interfere with planter operations. Consider the following before choosing this management option:

  1. Scout fields following harvest to determine whether winter annuals are present and if the weeds are exposed through residue cover. Waiting several weeks after harvest and re-scouting may allow residue to settle and weeds to grow through the cover. If most of the vegetation is covered by crop residue, it will be difficult to get sufficient coverage will a fall application.
  2. Some winter annual populations (e.g. marestail) may emerge both in the fall and spring, making effective control with a single herbicide treatment difficult. These populations may warrant a spring burndown rather than (or in addition to) a fall burndown.
  3. Follow herbicide label suggestions for carrier type, carrier volume, nozzle type, and environmental considerations. Treatments made on sunny days with warm daytime (>55F) and nighttime (>40 F) temperatures will generally be more successful than those made in cooler conditions. Winter annuals do not go dormant after a single hard freeze, so treatments can still be effective if milder conditions return.
  4. When selecting burndown treatments, consider the spectrum of winter annual and perennial species (e.g. dandelion) in the field. HG 91 (glyphosate) and HG 2 (ALS) resistant horseweed populations are widespread across the state. Including 0.5 lb. ae 2,4-D LVE or 0.25 lb. ae dicamba to glyphosate will increase the consistency of horseweed control, even in fields without glyphosate resistance. The addition of a residual herbicide in fall applications is not recommended due to the lack of consistent benefit and added expense. Residual herbicides are better left for spring herbicide applications, closer to the timeframe when most weed species are germinating.

Not all no-till fields require fall applications to control winter annuals. Situations that favor this tactic include: 1) history of high winter annual pressure, 2) presence of high weed densities at harvest, 3) presence of resistant biotypes that limit herbicide options in the spring, and 4) factors that prevent timely applications in the spring while weeds are small (poorly drained fields, sprayer availability, etc.).

Effective control of winter annuals prior to planting is an important first step for weed management in no-till, and in some fields, will benefit from a burndown application this fall.  While fall-applied herbicides will reduce the amount of vegetation present next spring, they rarely eliminate the need for controlling established vegetation at planting.

1HG refers to herbicide group. The Group number refers to the site of action of a herbicide. The Group number is displayed on the first page of the herbicide label and is important information for developing resilient weed management programs less likely to select resistant weeds.

Crops: CornSoybeanCategory: WeedsTags: winter annualsWeedsburndown treatment

Prioritize Pasture and Non-crop Weed Control!

ICM News - Fri, 09/30/2022 - 14:22

Fall is one of the best times for managing perennial and biennial weeds found in pastures or other areas maintained in perennial grass. As perennials prepare for the upcoming winter, they move energy reserves from shoots to their perennial vegetative reproductive structures (e.g. rhizomes, perennial rootstocks). Systemic herbicides applied at this time are translocated along with the energy reserves to the reproductive structures, therefore providing more consistent control than applications made at most other times of the year. As temperatures begin to cool, prioritize these applications before winter arrives to set up for cleaner fields next spring.

Caption: Controlling weeds in pastures increases the quality of forage available for animals.

The majority of herbicides used in pastures and other perennial grasses are growth regulator herbicides (Group 4)1. While products containing picloram (Tordon, Grazon P+D, etc.) and aminopyralid (Milestone, Forefront, Grazon Next HL, etc.) typically cost more than the “traditional” pasture treatment of 2,4-D and dicamba, they generally provide better long-term control of perennials like Canada thistle. Products containing metsulfuron-methyl (Group 2; Escort XP) provide an alternative to the growth regulators. 

The following are important considerations before making any applications:

       1. Scout the area to determine target weeds, their location, and the physical condition of their foliage.
               - While some fields may require a broadcast application, targeted treatments may be sufficient in others. Perennial weeds, such as Canada thistle, usually are found in distinct patches that facilitate spot treatments.
               - For effective control, weeds must have healthy foliage capable of absorbing and translocating herbicide to the roots. If extensive leaf damage is evident on the weeds, reduced herbicide absorption may diminish herbicide activity.

       2. Make applications on days with sunny conditions and daytime temperatures above 50-55 F whenever possible.

       3. Herbicide treatments, especially those containing growth regulators will kill legumes that have been interseeded with the grass.

       4. Read herbicide labels carefully to determine weeds controlled, appropriate rates, and any restrictions for treated areas. Residues of certain products (picloram, clopyralid, aminopyralid) persist in the foliage of plants in treated areas and can be moved with forage/hay bales or in waste (e.g. manure) of animals consuming the forage. The herbicide residues can damage sensitive plants (such as soybean) if moved from the application area with forage or livestock.

       5. While much of the state has been in drought this summer, most areas have received sufficient rainfall and cooler temperatures to allow recovery. Pasture species suffering from drought may be more susceptible to injury from herbicide applications.

Are applications still effective after frost?

Applications can still be quite effective after one or even several frost events. Pay attention to the principles above to create the best conditions for effectiveness, especially making sure weed foliage is in good condition and applications occur on warm, sunny days. Read more in this article “Effect of frost on pasture weed control.”

Caption: Foliage of weeds must be in good condition to obtain effective control.

Rather than simply applying a herbicide to eliminate weed problems in pastures, take time to determine why the weeds are successful in the field. A healthy sod should be able to prevent the establishment of most weeds. Evaluate soil fertility, stocking rates, and determine the need for overseeding to thicken the grass; this article discusses some considerations for pasture improvements. Herbicides are valuable tools for improving pasture quality, but they are not a substitute for good management practices.

1The Group number refers to the site of action of a herbicide. The Group number is displayed on the first page of the herbicide label and is important information for developing resilient weed management programs less likely to select herbicide-resistant weeds.

Crop: Biomass and ForageCategory: WeedsTags: pasture weedspastureperennial weeds

Keep Monitors, Sensors and Scales Accurate During Harvest

ICM News - Thu, 09/29/2022 - 08:46

When heading to the field for harvest, it’s important to make sure your monitors, sensors and scales are getting accurate numbers. Taking the time to calibrate your combine yield monitor is the first step in making sure you are using high quality yield data to make decisions in your operation.

Iowa State University’s Digital Ag team provides an online interactive monitor guide with step-by-step instructions for operating your displays. Use this tool for directions on how to calibrate your combine’s yield monitor. 

Most yield monitoring systems require a calibration process (single or multipoint calibration). It’s important to know what type of calibration process your particular yield monitor requires. Refer to the manufacturer’s guidelines to be sure you are meeting or exceeding those requirements. Some manufacturers now offer yield monitors with self-calibrating systems that require little to no input from the operator.

A typical calibration process requires three steps:

  • Harvest a calibration load. 
    • For multi-point calibrations these loads should be between 3,000 to 6,000 lbs. 
    • For single-point calibrations these loads can be larger, up to a full grain tank.
  • Weigh the calibration load on a grain cart or truck to get a ground truth weight for the load.
  • Enter the ground truth weight into the yield monitor display

This process is repeated for multi-point calibrations using different crop flow rates.

Is Your Scale Accurate?

No matter the make and model of your yield monitor, a scale system is needed to get a “ground truth” load weight. There are many ways to accomplish this, including using seed buggies with scales, grain carts with scales or truckload scale tickets from an elevator. When collecting ground truth load weights for your yield monitor calibration it is important to verify that the scale system you are using is accurate, or you could be introducing more error into your yield data.

Grain Cart Scale Tip: Most growers verify their grain cart scales against truck load net weights from elevator scale tickets. This is a good practice and an easy way to ensure your grain cart scales are still accurate throughout the season. However, when using your grain cart to calibrate your yield monitor, consider leaving the grain cart half full when collecting ground truth weights. This will ensure the weight range on the grain cart scales is closer to the full cart weight values that you have been verifying against elevator tickets.

Why A Calibration Process Matters

Most yield monitor systems used today have the ability to utilize a multipoint calibration process. This is typically more accurate than using a single point calibration process. The multipoint calibration will better capture and quantify the variability across a field.

Yield monitors calculate yield based on fluctuations in mass flow rate. The yield of any crop will naturally fluctuate throughout a field due to a host of agronomic factors. This means that even if you drive at a constant speed with the combine, the actual flow rate or through-put of the combine will fluctuate as the yield changes. It’s important to have calibration points for these different flow rate ranges to ensure the yield monitor is accurately calculating yield.

Changes in flow rate can be simulated for calibration purposes by driving at different ground speeds through an area of the field with consistent yield. It’s important to drive a consistent ground speed for the entire calibration load. Collect several calibration loads at your normal operating speed (for example, 4 mph), then, capture calibration loads at slower and faster ground speeds (for example 2, 3, and 5 mph). This process will fluctuate the flow rate through the combine and ensure that you have multiple points throughout the calibration curve.

Failing to calibrate at multiple flow rates will result in less accurate field totals and spatial distribution of yield on a yield map.

Recalibrate when Crop Moisture Changes

Recalibrating your yield monitor throughout the harvest season when crop conditions change is critical to maintaining yield map accuracy. Changes in grain moisture can affect the accuracy of the calibration, and as your crop continues to dry down later in the season the yield monitor’s sensor will react differently. Yield monitors in corn are particularly sensitive to moisture changes. Corn that is harvested above 20% moisture will require recalibration every 2.5% change in moisture to maintain yield monitor error of less than 5% (Figure 1).

Figure 1: Corn moisture influence on yield monitor error.

As the season progresses, pay close attention to the mechanical components of the grain handling and yield monitor system. Inspect the sensor periodically for dirt buildup or other debris obstructing it. Regularly check for proper tension on the combine’s clean grain elevator chain, as this is critical in maintaining consistent yield monitor accuracy. If you re-tension the clean grain elevator chain it is recommended that a new yield monitor calibration be performed.

Yield monitors are an incredibly valuable tool for farmers if properly calibrated and maintained throughout the harvest season. While the initial calibration process and confirmations through the season require time, farmers will reap the rewards of careful planning with high quality yield data.

Crops: CornSoybeanCategory: Crop ProductionEquipment and MachineryTags: yield monitorharvest datayield

6 Simple Tips for a Safe Harvest This Fall

ICM Blog - Tue, 09/27/2022 - 09:08

Safety should be a major concern for all farmers during harvest, but as the season goes on, it can be easy to miss details or neglect safe practices that can put you or others at risk. Here are six simple safety tips to maintain throughout the season to keep yourself and your crew out of harm’s way.

1. Keep your machine’s safety features, mirrors and windows clean both in and out of the field

Grain carts are one of the most used pieces of equipment during harvest, but they also have the most potential for blind spots. With few lights on the back of the cart and large areas of obstructed visibility, it’s important to keep the safety features available in good working order. Check your cart’s turn signal and brake lights prior to leaving each field to ensure safe operation down the road.

Be sure to regularly wipe any dust or debris from safety reflectors, lights and mirrors on your harvest equipment both in the field and on the road. If your grain cart or wagon doesn’t come with turn signal lights, a magnetic strobe light like this one can be used to make your implement more visible from the rear in low light situations. Keep glass cleaner and paper towels or rags in your cab to clean your machine daily and prevent accidents that can occur from not seeing a car or other obstacle on the road.

Figure 1. Replace any reflectors that are not in good condition at the start of harvest season and clean reflectors and lights regularly.


2. Inspect your PTO’s safety shields for all operation

The Power Take Off (PTO) can cause severe injury without proper safety precautions. NEVER step over the PTO shaft, either while it is running or when it is not in operation. This includes a tractor and grain cart combination, combine header PTO shafts and tractors attached to an auger that might be running at a bin site. It is always better to take few extra seconds and walk around the equipment.

Inspect the guards on the PTO shaft every season. With the tractor/combine turned off and the key stored in the operator’s pocket, use one hand to spin the shield 360°. If the guard can spin without stopping or turning the power drive train, the shield is working properly. If the guard does catch or rub at any point in time, the guard should be repaired or replaced before being put back into service. Don’t forget to check the PTO shafts on the combine head as well to prevent crop from getting tangled around the shaft.

3. Look out for rocks and other debris in crop fields

Be observant as you harvest your fields and watch out for rocks or other large debris that could seriously damage your machines and slow down your harvest. If you do experience a plug in your corn head, follow this procedure to safely remove it. 

  1. Bring the combine to a stop and back up a few feet so the head of the combine is located over harvested crop.
  2. Bring the combine’s threshing element to a slow speed on idle.
  3. Open the deck plates as wide as they will go.
  4. Using the reverser switch for the head, lightly bump the switch in reverse a few times to see if the plugged material becomes dislodged. If the material does not become dislodged, stop running the head. Constant running of the head can cause damage to the slip clutch, making it weak and creating excess heat.
  5. Follow the combine lockout procedure before ever working around or under a raised combine head. Make sure all hydraulics and shafts are removed from the combine and safety cylinder block/stops are applied.
  6. Using cut resistant gloves, grab a handful of material at a time and slowly begin pulling it out of the snapping rolls. Be careful; debris lodged in the snap rolls could be sharp.

4. Be aware of your crew’s location

A good practice is to honk the horn of the combine or tractor three times before starting the machine or engaging the components so other members of your crew know the machine is moving, and to give them time to move out of the way and remove themselves from moving parts.

5. Check your tow ropes and chains when extracting stuck equipment

While not every area in the state may have this problem each season, it’s important to know how to stay safe when pulling out a stuck tractor or combine. When possible, use tow ropes in good condition instead of chains. If only chains are available, inspect them to make sure both ends are in good condition and the chain itself does not have any broken, bent, or weak links. Be sure that the machine you pull with and the chain are large enough to tow the weight of the stuck machine. Never stand between a stuck vehicle and the implement towing it. Chains and ropes can break and will seriously injure anyone in their path. It’s best to stand far way and communicate with the operator of the equipment using either cell phones or two-way radios.

6. Be conscious of your mental health and seek help when necessary

There is a growing concern about mental health in the agriculture and farming community, and the harvest season can cause additional stress. Be mindful of your own mental health, as well as that of your employees, co-workers, and family. For help dealing with stress, disaster relief, and legal matters, refer to www.extension.iastate.edu/iowaconcern/ or call 1-800-447-1985.

Continue to keep up with these practices as you go through the harvest season. By using these tips and maintaining awareness of your surroundings, you can protect yourself, your investment and others on the road and in the field for a safe harvest season.


Category: Crop ProductionEquipment and MachineryTags: harvestharvest safetycombineDigital AgAuthors: Ben CovingtonRyan W BergmanMatt DarrCrop(s): CornMinor cropsSoybean

Sap Beetles in Corn: Are they Pests?

ICM News - Fri, 09/23/2022 - 11:06

Sap beetles are a relatively common insect in cornfields, typically seen each year around harvest. People usually notice sap beetles (and other ear-feeding pests) while doing pre-harvest yield checks. Adult sap beetles are usually less than ¼ inch long and oval. Most are dark colored and sometimes have orange or yellow spots (Photo 1). Sap beetles can be distinguished from other beetles in corn by their antennae, which have a knob at the end. Larvae may also be found on corn ears. The larvae are small and white with a light brown head, and they turn yellowish as they mature.

Photo 1. Picnic beetles are a type of sap beetle often found in cornfields. (Photo by Joyce Gross, UC Berkeley.)

But are sap beetles pests of corn?

The answer is a bit complex. Sap beetles are scavengers, typically feeding on decaying plant matter, over-ripe fruit, and plant sap. In corn, sap beetles are almost always a secondary pest, meaning they begin feeding on corn ears only after the ear is already damaged. They typically hollow out kernels, usually at the ear tip.

Most often, sap beetles will colonize corn ears where caterpillars were feeding, such as corn earworm. Because of this, we rarely consider sap beetles to be an economic pest of corn, but its association with other harvest issues can lead to concern. The damage from any ear-feeding insect creates a wound where ear rots and mycotoxins can develop (Photo 2).

Photo 2. An example of ear molds that can develop after insects feed on the ear. (Photo by Meaghan Anderson.)

If you are experiencing high numbers of sap beetles feeding on ears:

  • Consider harvesting those fields early to shorten the time sap beetles are feeding on corn or prevent the development of ear molds prior to harvesting;
  • Change combine settings to try to blow out beetles and damaged kernels;
  • Monitor grain for the presence of sap beetles, especially if grain will go directly from the field into a grain bin for storage. Insecticide treatments may be necessary to prevent beetles from feeding on stored grain.
  • If grain will be dried, make sure to use a high temperature drying operation to kill beetles before storage. Anecdotes from last fall suggest some sap beetles can survive low temperature drying operations.

Sap beetles that are not removed with the crop during harvest will seek sheltered sites (e.g., wooded areas or plant debris) for overwintering soon. Make sure to monitor grain for presence of sap beetles or ear rots prior to storing or marketing.

For subsequent growing seasons, you can reduce the risk of sap beetles a few ways. Consider a corn hybrid with effective Bt traits for corn earworm and other ear-feeding caterpillars to minimize feeding by secondary pests. Additionally, some corn hybrids are more likely to have exposed ear tips than others. Minimize ear tip exposure by choosing a hybrid where the tip of the ear is not as exposed.

Crop: CornCategory: Crop ProductionInsects and MitesTags: sap beetlecorn insectscorn mold

Fire Prevention and Safety Considerations During Harvest

ICM Blog - Tue, 09/20/2022 - 09:00

All it takes to start a fire is just a spark from an engine, an overheated bearing on a combine, or a hot exhaust manifold where some dirt and dry plant material have gathered. Dry plant residue, dusty conditions, low humidity levels and strong winds are a recipe for combine and field fires. During harvest periods with increased fire potential, fires cause millions of dollars in property damage in Iowa, including loss of machinery, crops, and time. Supply chain issues and limited availability of parts may only further plague down equipment. Injuries to farm workers and firefighters are also an unfortunate outcome in some instances.

Modern, high-productivity combines are powerful machines; power means heat. A fire cannot start without heat and fuel. You may not be able to remove the heat from the engine, hydraulics, and other hard-working systems, but you can remove the fuel source by keeping your combine and other equipment clean.

The potential risk for combine and field fires is always higher during harvest, but it doesn’t have to be. Taking a few minutes and following these steps and management tips could significantly help mitigate these risks.

Prevention tips:

  • Keep the machine clean, particularly around the engine and engine compartment. Use a high pressure washer or compressed air to remove caked-on oil, grease, and crop residue.
  • Frequently check air filters, ensuring that they stay clean; either by blowing them out or replacing them. This will help the engine run cooler and more efficient.
  • Check coolant and oil levels daily. Pay close attention to engine and hydrostatic pump parts as well.
  • Check the pressurized oil supply line to the turbocharger for wear areas that rub and may start an oil leak.
  • At the end of each day blow leaves, chaff and plant material from the engine area with either compressed air or a portable leaf blower. Waiting until the next morning to do this may be more difficult because of the dew.
  • Remove plant materials wrapped on or near any bearings, belts, chains, or other moving parts.
  • Examine the exhaust or any hot bearing surfaces. Repair leaking fuel or oil hoses, fittings or metal lines immediately.
  • Inspect and clean ledges or recessed areas near fuel tanks and lines.
  • Prior to refueling, turn the combine off and wait 15 minutes to reduce the risk of a spill volatilizing and igniting.
  • Research from South Dakota State University suggests that if we have dry conditions and start experiencing wind speeds close to 30 mph and above, fires may be inevitable. During these periods producers should consider delaying harvest until evening hours when winds decrease or wait for precipitation. Higher humidity levels may also reduce the potential for field fires to spread.

Management tips:

  • In case of fire, turn off the engine, get away from the machine, and call 911. Then attack with fire extinguishers if it is safe to do so. Try to fight from the “black," the area already burned. Attacking a fire from areas with combustibles (e.g. dry corn stalks) is much riskier. Always stay upwind of a fire to minimize the risk of exposure from smoke, heat, and possible flames.
  • A fire can double in size in less than a minute. Burning embers blown downwind can easily spread a fire well beyond the control of your fire extinguishers in just seconds. So be aware of possible additional fires.
  • It is recommended to have two ABC-rated fire extinguishers on hand: a smaller 10-pound unit in the cab and a larger 20-pound extinguisher at ground level on the combine. Keeping an extra fire extinguisher on other pieces of machinery or trucks that are out in the field is also a good idea.
  • Invert the fire extinguisher once or twice during the season to ensure that machine vibrations don’t compact the powder inside.
  • Keeping a shovel on the combine to throw dirt on a fire can also help.
  • Create a list with the 911 addresses for each of your field locations prior to harvest and have them easily accessible to family members and farm employees. Many fire departments are equipped with GPS equipment or mobile apps to assist in directing them to incidents. When a fire is called in with a 911 address, dispatch can more readily identify the incident location and relay this information to the fire department. This can save precious time as some fields may be in remote locations.

Create an emergency plan:

Fires can start from plant materials that may have been smoldering unnoticed for 30 minutes or more. The ignition source for field fires may have been the earlier passing of a truck, tractor, or combine. Flames may not be apparent until additional oxygen is supplied, perhaps by a gust of wind. Harvest crews and neighbors may want to discuss a plan for emergency tillage of a firebreak should that option become advisable. The goal of creating a firebreak with a tillage pass; is to stop an out-of-control fire from spreading. It creates an area that won’t fuel the fire, so the fire will eventually burn itself out.

Keep in mind that personal safety is far more important than property loss. Attempting to fight a fire should only happen after calling 911 and determining that it’s safe to do so. Fire prevention is possible; it just requires some regular maintenance and keeping equipment clean.

Category: Crop ProductionEquipment and MachineryTags: Fire Prevention; Combine Fire; Harvest SafetyAuthor: Joshua MichelCrop(s): Corn

The 2022 growing season challenges continue: ear, crown and stalk rots.

ICM Blog - Mon, 09/19/2022 - 09:22

It’s hard to believe another growing season has come and is almost gone. 2022 has had its share of challenges: a wet start, drought, corn root worm, soybean gall midge, pigweed, and (my favorite) tar spot. And now, as we approach harvest, we face final challenges like ear and crown rot.


Ear rots

There are some ugly ears out there, particularly in the localized areas that received hail during grain fill. In 2009, we documented increased ear rot and mycotoxin-contaminated grain in fields damaged by hail at growth stages R1-R3 at compared to fields with no hail damage (Robertson et al. 2010). Iowa State University extension field agronomist Meaghan Anderson scouted fields near Zearing and reported various ear rots (Fig 1.)

It is important to scout fields for ear rots, and identify them correctly, because some ear rot fungi produce mycotoxins. Additionally, insurance companies may require the damage to be adjusted in the field prior to harvest. Grain with high levels of mycotoxins may be docked at the elevator, or worse still, rejected. A publication from the Crop Protection Network can help you identify what ear molds and associated mycotoxins may be present in your field: An Overview of Ear Rot

For fields in which >10% of the ears are moldy, schedule an earlier harvest. Fungi that cause ear molds will continue to grow and produce mycotoxins in the field. Store grain from moldy fields in a separate bin. Dry (<15 % moisture), and cool (<55F) the grain as quickly as possible to stop fungal growth and further mycotoxin production.

Fig. 1. Ear molds associated with hail damage to a corn ear. (photo courtesy of Meaghan Anderson)

Crown rot

I am starting to hear reports of crown rot. Symptoms of crown rot include “ghosted” (premature death) plants (Fig. 2), and when the plant is split longitudinally, the crown tissues are dark brown-black and rotted (Fig. 3). Some hybrids are more susceptible to crown rot. Very wet conditions soon after planting followed by stressful conditions during grain fill are believed to favor crown rot.

Fig. 2. A “ghosted” plant is an indication crown rot may be present.

Fig. 3. Dark brown, rotted crown tissues are symptomatic of crown rot.

Stalk rot

Ghosted plants may also be an indication of stalk rot. Stressful growing conditions affect photosynthesis. Reduced photosynthesis results in cannibalization of stalk sugars to support grain fill. Consequently, stalk tissues are more at risk for colonization by stalk rot fungi.


Fields that have >10% of ghosted plants, may need to be scheduled for harvest earlier since standability will be compromised.


References Cited

Robertson, A.E., Munkvold, G.M., Hurburgh, C., and Ensley, S. 2011. Effect of natural hail damage on ear rots, mycotoxins and grain quality characteristics of corn. Agronomy Journal 103:1193-1199







Category: Plant DiseasesTags: crown rotear rotstalk rotharvest issuesAuthor: Alison RobertsonCrop(s): Corn

Regional Update: Sept. 6 - Sept. 13, 2022

ICM Blog - Tue, 09/13/2022 - 13:54

As the growing season winds down, ISU Extension field agronomists share what they are seeing out in fields or are getting questions on. Some of the common observations include the drought stress resulting in crops shutting down early, tar spot becoming more prevalent in fields, sudden death syndrome in soybeans, and plenty of waterhemp escapes. Read on for more specifics across the state.   

North Central Iowa

Angie Rieck-Hinz (Region 3): “Nearly all of my counties caught some much-needed rain over the weekend, from 0.68 inches at Mason City to 0.92 inches at Fort Dodge. And while that rain came too late for most of the corn, it may have helped some later maturing soybeans. Corn is mostly at R5.75 and some is at black layer from early senescence due to lack of moisture. Corn grain harvest has begun south of Fort Dodge and corn silage harvest has been in full swing for the past 10 days. I don’t have any yield reports as of today. I have been scouting corn fields for late season diseases and have found northern corn leaf blight, gray leaf spot, common rust and tar spot. The worst I have seen tar spot is shown in the photo below. This photo is taken of one leaf below the ear leaf.  While I can find tar spot lesions on the ear leaf and above, the incidence and severity has been low, and this observation holds for both fields with a fungicide and fields without a fungicide applied. Soybeans are R6 (full pod) to R7 (beginning maturity). There is some sudden death syndrome (SDS) present in soybeans this year. 

Tar spot on corn near Bolan, (Worth County) Iowa.  Photo courtesy Angie Rieck-Hinz.

 Northeast Iowa

Terry Basol (Region 4): “Corn and soybeans for NE Iowa look good going into fall right before harvest. Corn fields for the area are in the R5 (dent) stage and range anywhere from ¼ to ½ milk line, respectively. On average, we’re still looking at needing about 15-20 days to get to R6 (physiological maturity). The cooler temperatures have helped lower plant stress, which helps with kernel dry matter accumulation, directly helping test weight.  We have seen tar spot incidence develop later this season due to conducive environmental conditions. Research shows that a fungicide applied at VT – R2 is still the best timing, and it is too late if applied during thr R4 and R5 stages. Soybeans are primarily in the R6 stage (full seed pods contain green seeds that fill the pod to capacity at one of the four uppermost nodes on the main stem.). Most of the fields in the area are starting to turn. In general, foliar disease pressure for soybeans has been low, but we have seen some isolated areas of sudden death syndrome and brown stem rot. As far as precipitation, we received some welcome precipitation over the weekend. According to the Iowa Mesonet, the NE Iowa Research and Demonstration Farm at Nashua has received 0.9 inch of rain since September 1st.

Josh Michel (Region 5): “Over this past weekend, most of NE Iowa received anywhere from 0.25 to 0.50 inch of rain. Before this weekend’s rain, farmers have been able to take advantage of several days of dry weather. Most of the corn in NE Iowa is currently at R5 (dent), ¼ to ½ milk line. Silage harvest has been ongoing in many areas as weather and field conditions have allowed. Soybeans are mostly at R6-R7. I continue to see and hear about reports of SDS showing up in a few areas. Alfalfa forth crop harvest is taking place in many areas. Potato leafhoppers and grasshoppers continue to be the main pests being scouting for. Pastures are in good to excellent condition with consistent rains and cooling temperatures. Most of my field calls over the past week have consisted of silage harvest timing, forage management, alfalfa pests and scouting, as well as weed management in pastures.”

Alfalfa fourth crop harvest taking place in an alfalfa field in NE Iowa. Photo courtesy of Josh Michel.

 Central Iowa

Meaghan Anderson (Region 7): “Central Iowa received some welcome rainfall in late August and early September to help finish out this crop and we hope it translates to larger soybean seeds and corn grain. Parts of central Iowa, particularly eastern Warren County, SE Polk County, and southern Jasper County received recent rain but remain dry. Corn is mostly between ½ milk line (R5.5) and physiological maturity (R6). Tar spot and waterhemp are both easy to find in fields now. Grasshoppers are prevalent on some field edges. I’m concerned about stalk integrity as we approach harvest in many fields; with the significant nitrogen deficiency symptoms and late tar spot coming into some fields, stalk rot assessments will be important to help determine harvest order. Soybeans are changing quickly across my area but some of the replanted areas are still bright green. The most apparent thing in central Iowa soybean fields is waterhemp above the canopy. Field calls have been on pasture weed management, tar spot, poor corn pollination, and fertility.”

Heavy waterhemp pressure under corn canopy. Photo courtesy of Meaghan Anderson.

Waterhemp above the soybean canopy in a central Iowa soybean field. Photo courtesy of Meaghan Anderson.

 East Central, Southeast, and South-Central Iowa:

Rebecca Vittetoe (Region 8): “Over the weekend we received some welcomed rained in EC Iowa. Rainfall totals ranging from 0.5 inch to 1.5 inches. Most of the drier areas in my region that had been showing up on the US Drought Monitor as being in a severe or moderate drought received almost an inch of rain or more. Corn ranges from about ½ milk line (R5.5) to physiological maturity (R6). Some fields in the drier parts of my area did shut down early. Tar spot is becoming more prevalent in fields across EC Iowa. Also, as we head into harvest, do keep an eye out on stalk quality this fall. A lot of soybean fields turning as well. I’ve been seeing some sudden death syndrome and frogeye leaf spot in soybean fields. It’s also not hard to spot waterhemp that escaped this growing season in soybean fields and even some corn fields. Calls have mainly been on pasture weed management or preparing for pasture renovations next year, tar spot, cover crops, and  weed ID.”  

Virgil Schmitt (Region 9): “Rainfall in the last 30 days in the counties I cover was about 1.0 inch south of Highway 92 to over 6.0 inches near Highway 30. Areas roughly south of Highway 92 are listed as DO (abnormally dry) to D2 (severe drought) on the September 8, 2022 Drought Monitor. In general, temperatures during the last month in the counties I cover were one to three degrees below normal. Most corn is R6 or within a few days of R6 and looks good to excellent except for areas showing drought stress. There are low levels of gray leaf spot and northern corn leaf blight in some fields and tar spot can be found here and there. Most soybeans are at R6 and also look good to excellent except for areas showing drought stress. Again, disease levels are very low. However, there is considerable white mold in Cedar County. Potato leafhoppers continue to be present in alfalfa and there are winged grasshopper adults in grassy areas. Phone calls, emails, and field visits last week mostly involved weed management and cover crops.

Rainfall totals across the state for the last 30 days. Source: https://mrcc.purdue.edu/CLIMATE/Maps/stnMap_btd2.jsp

Check out the map below to find your local ISU Extension field agronomist and find their contact information here!

Category: Crop ProductionTags: regional updateCornsoybeanstar spotharvestAuthor: Rebecca Vittetoe

Making Yield Estimates in Corn - 2022 Edition

ICM Blog - Fri, 09/09/2022 - 08:19

Again this August, I joined my colleague Patrick Hatting, Farm Management Specialist for central Iowa, and checked several Polk County corn fields to make yield estimates. After R3 (milk stage) is a great time to venture into corn fields to make yield estimates as kernel abortion is less likely and plant stress will result in reduce kernel size or fill rather than kernel loss. In addition to performing yield checks, walking late reproductive corn provides a good opportunity to check the field for other things like stalk rots or other standability issues and foliar disease, especially if you left any test strips of untreated vs. fungicide-treated areas of fields. These late-season checks can be invaluable to plan for harvest and future years.

Patrick and I visited 10 corn fields in Polk County on August 25 to do yield estimates. In each field, we arbitrarily chose a location sufficiently far from the field edge or any confounding areas (waterways, demonstration plots, etc.). While other methods exist, the most common method of making yield estimates is the traditional “yield component method.” If you’re interested in the full details on estimating yield using this method, check out this ICM Encyclopedia article on the topic.

Steps to estimating yield using the “yield component method”:

  1. Measure 1/1000th of an acre and count number of plants with harvestable ears. In 30-inch row corn, 1/1000th of an acre is 17 feet, 5 inches.
  2. Choose several ears in the 1/1000th of an acre to count kernels on. We chose 6 per measurement and selected them by choosing every 5th harvestable ear. You can choose any method, but we suggest using a method to remove some subjectivity from selection and try to reduce the chances of biasing your sample.
  3. Count the number of kernel rows around each ear and determine the average number of kernel rows around.
  4. Count the approximate number of harvestable kernels on the length of each ear and determine the average kernels per row.
  5. Use the following math equation to determine an approximate yield for the field based on your sample: 
  6. Collecting more ears per sample and more samples from an individual field should lead to a more accurate representation of yield. A more thorough yield estimation might use 10 ears per sample and collect samples from 5 different areas of the field.

One hotly debated topic is the appropriate denominator number to use for the kernels per bushel in the yield component equation. 90,000 has always been a standard used in this equation, but more updated sources suggest that modern hybrids may have fewer kernels per bushel. The key factor is that this number is simply assumed and is likely to be variable based on corn hybrid and environmental conditions during grain fill. In years with significant stress during grain fill, kernels are likely to be smaller and that denominator of kernels per bushel may need to be higher – perhaps 100-120,000 kernels per bushel. In other years, the number could be lower than 90,000. This can be especially challenging when trying to determine a yield estimation but is an important note since so much of yield depends on kernel size and kernel fill during the later reproductive stages.

Remember that yield estimates are just that – yield estimates. Last year, the average yield of our 9 estimates using the yield component method was 217 bu/ac in Polk County and USDA-NASS reported the average yield in Polk County to be 218.6 bu/ac. This year, the average yield across our 10 estimates was 191 bu/ac, much lower than 2021. The graph below demonstrates the accumulation of growing degree days (GDDs), precipitation, and stress degree days (SDDs) in 2021 and 2022. While the 2021 and 2022 lines run very similarly through the season, the slight differences in timing of rainfall and more stress degree days in 2022 are likely related to the lower yield estimates this year.

May 1 to Sept. 7 growing degree day accumulation, precipitation, and stress degree days for 2021 and 2022. Source: Iowa Environmental Mesonet.

Be sure to note areas where yield estimates are made in order to make comparisons after combines have run; you may be able to approximate the number of kernels per bushel and see how close you were to the correct number (for this year, and this hybrid).

See the 2021 article here and contact your local Iowa State University Extension field agronomist to let them know about your corn yield estimates!

Category: Crop ProductionTags: corn grain yieldscorn yield predictionestimating yieldsyield componentsAuthor: Meaghan AndersonCrop(s): Corn

Time to get your grain bins ready for harvest

ICM Blog - Tue, 09/06/2022 - 16:15

Before the rush of harvest gets here, take some time to get your grain bins ready for a new crop. The first step in minimizing grain spoilage from insects is to start with a clean bin. Grain-feeding pests can survive on residual grain, broken kernels, fines, foreign material, and molds accumulated inside grain bins and around the bin perimeter. To reduce infestations, limit accessibility by sealing gaps and cracks, cleaning grain-handing equipment, remove all potential food sources, and in some cases applying insecticides.  

Check mechanical parts of the bin while it is empty and conduct any maintenance needed before new grain is stored. Seal any gaps or cracks along the bin to prevent insect and moisture entry. Check the roof closely around the vents or access doors, as those are common spots for leaks. Also clean out harvesting and handling equipment, like combines, trucks, wagons, and augers, to remove all dust and debris that can harbor mold and insects.

Sweep the bin walls and floor, make sure to clean the tops of doors, inside hollow pipes or ladders, and inside of augers. If possible, remove the aeration floor and clean out all accumulated food materials. Some bin designs make under the floor cleanup a bit easier with removable floor panels throughout the bin or blow-out doors that can be opened to blow out material accumulated below the floor. If fines or Indian meal moth silks are starting to plug up the space below the floor, it is time to remove the floor to vacuum or power wash.

Trim down vegetation around the bins, equipment, and storage buildings to reduce any potential refuge areas between seasons. Remove any residual grain or debris around the bin. Consider using a rodenticide around the bin’s outer perimeter.

If the aeration floor can’t be removed, fumigation is the best option to eliminate carryover insects. Strongly consider fumigation if insect activity caused issues for recent grain in storage. Follow label instructions and use extreme caution when applying fumigants or consider hiring a trained and licensed fumigation specialist. Consider an insecticide application to the clean walls and floor in the bin and around the exterior perimeter, especially if you are considering storing grain past the spring into summer months. Some insecticides could also be applied to grain as you fill the bin or as a surface application, such as insecticides for Indian meal moths. Oklahoma State University Extension officers excellent insecticide and fumigant recommendations for grain protectants and grain storage facilities.

When adding a new crop to the bin, use these three basic grain storage principals to prevent storage quantity and quality loss:

  1. Store clean grain
    • Use proper combine settings to limit grain damage and reducing the collection of fines and foreign materials.
    • Clean the grain before putting it in the bin if fines are still a problem after adjusting combine settings.
    • Minimize drop height in the grain system and reduce kernel damage by using cushion boxes to minimize grain-on-grain contact.
    • If a grain spreader is not used, core the grain mass multiple times as the bin is filled to remove fines, broken kernels, and foreign materials that naturally accumulate in the center core. A level surface will also improve aeration through the grain mass.
  2. Store dry grain
    • Follow grain storage moisture content (MC) recommendations, which are typically recommended as 15% for corn grain stored through the winter and 13% when stored past the spring into summer. For soybeans, MC recommendations would be 13% and 11%, respectively.
  3. Store cool grain
    • Cool grain to below 40 degrees F as soon as ambient temperatures will allow in the fall. Insect development, including feeding, is reduced below 50 degrees F as insects become inactive. If grain is binned when temperatures are still warm, plan to cool the grain every time the ambient temperature is 10 degrees F lower than the grain temperature until grain is cool for winter storage.
    • Run a full cooling cycle for aeration fans. Check that the grain at the top of the bin is cool, as this is the last grain to cool when fans push air up through the grain.
    • Run aeration cycles throughout the storage period to ensure grain temperature remains cool and even throughout the grain mass. Grain under the roof and near the walls can collect solar heat as the roof and wall steel is warmed by the sun.
    • Find more information on cooling grain in the fall here.

Seal aeration fans when not in use to prevent warm or moist air and insects from entering the grain mass. Monitor grain at least every other week to check for insect activity and signs of spoilage, such as crusting, damp/warm spots, musty or sour odors, or rising CO2 levels with a handheld CO2 monitor.

Follow these good grain storage principles when storing grain to avoid grain quality loss and subsequent issues with grain flow during unloading. If grain quality issues are discovered during unloading, be extra careful to avoid dangerous situations that could lead to engulfment or entrapment. Learn more about grain safety tips in a recent article here.

Additional resources:

Cool stored grain now | Integrated Crop Management (iastate.edu)

Don’t become a statistic: Grain bin safety tips | Integrated Crop Management (iastate.edu)

Iowa Grain Quality Initiative: https://www.extension.iastate.edu/grain/

Category: Grain Handling and StorageInsects and MitesTags: grain bingrain storageinsect managementAuthor: Kristina TeBockhorstCrop(s): CornMinor cropsSoybean

The Time for Seeding Cover Crops is Upon Us

ICM Blog - Fri, 08/26/2022 - 07:30

As we enter the time for aerial and broadcast overseeding of cover crops, now is a good time to think about how current weather, soil and crop conditions might affect things. First and foremost, there are parts of the state that are very dry and others that have been getting timely rains. Rainfall and soil moisture are important factors in establishing cover crops. Dry conditions, especially for overseeding situations, could cause delays with seed germination and, therefore, establishment will be less than ideal. Here are some considerations for seeding into dry conditions.

  • Postpone overseeding until rain chances improve for improved odds of germination
  • Consider drill seeding after harvest has occurred to achieve better seed to soil contact
  • Switch to cereal rye for improving overwintering survival

Another consideration that may need to be factored in is herbicide carryover. With the start of planting being delayed and lack of mid-summer soybean canopy cover, there were some later than normal herbicide applications. If those later herbicide applications had residual activity, combined with drier weather, there could be herbicide carryover that could reduce cover crop seed germination and establishment. Some species are more tolerant (cereal rye), and others are less tolerant (radish). Use caution where residual herbicides were used and consider switching to cereal rye for successful establishment.

Spring cereal rye growth following overseeding into preharvest corn.


Relevant Resources

Considerations When Overseeding Cover Crops

Tips and Considerations for Getting Started with Cover Crops

Category: Crop ProductionTags: cover cropsseeding cover cropscover crop establishmentAuthor: Mark LichtCrop(s): Cover Crop

Should I apply a late season fungicide for tar spot?

ICM Blog - Wed, 08/24/2022 - 15:54

I continue to receive tar spot reports from across Iowa. Given the moisture we have had the past couple of weeks and the growth stage of the crop, this is not surprising.  Tar spot development is favored by leaf moisture. As the growing season progresses, tar spot inoculum likely increases, the efficacy of many fungicides applied earlier in the season start to wane, and consequently we start to see more disease develop.

I have seen the best development of tar spot in my trials at the ISU Southeast Research Farm near Crawfordsville. Last week (August 18, 2022), average tar spot severity on the ear leaf of corn not sprayed with a fungicide was 1 to 2% (Fig. 1). The growth stage in my trials was R4-R5.

Figure 1.  Diagram showing 2% tar spot severity (from www.cropprotectionnetwork.org)

There have been questions regarding an application of fungicide at R4 to R5 to protect the crop through physiological maturity. Dr. Darcy Telenko at Purdue University shared some fungicide data from her fungicide timing trials in Indiana over the past three years (2019, 2020 and 2021). She found that applications at VT to R2 were best, while little control was achieved with applications at R4 and R5 (See slide 40).

Based on these data, if you have tar spot developing in your fields now, there is little you can do to control the disease this growing season. Rotating to soybean in the following year may help reduce the tar spot inoculum in that field. Another consideration is to plant a tar spot tolerant hybrid in that field and surrounding fields.  Some seed companies will have tar spot scores for some of their hybrids in the coming year.


Category: Plant DiseasesTags: tar spotfungicideAuthor: Alison RobertsonCrop(s): Corn

New Iowa counties confirmed with soybean gall midge in 2022

ICM Blog - Wed, 08/24/2022 - 08:19

Several labs in the Midwest have been monitoring the distribution of soybean gall midge in Iowa since 2018. Last year, we sampled many counties in western Iowa but only confirmed three new counties. This year, we focused on the counties just east of the distribution in 2021 and were able to confirm eight new counties in Iowa that had soybean gall midge: Humboldt, Kossuth, Palo Alto, Pocahontas, Polk, Ringgold, Warren, and Webster (Figure 1). Iowa now has 42 counties confirmed with soybean gall midge, nearly half of the state. To see the distribution in other states, visit our regional website (155 total counties in five states).

Figure 1. Counties with soybean gall midge in Iowa (as of 22 August 2022). Orange highlighted counties were confirmed in 2022. Gray counties were scouted but not confirmed.

In the newly confirmed counties, we stopped in random soybean fields on the western half of each county. We prioritized soybean fields that shared a border with a cornfield (see explanation below). Once we found an ideal field, we checked plants at the edge (next to corn) for dead/dying plants, wilting, or black lesions at the base of the stem. If lesions were found, we pulled the plants and opened the lesions to confirm that soybean gall midge larvae were inside (Photo 1).

Photo 1. Black lesions form at the base of the plant near the soil line (left) as a result of larval feeding injury. When the lesions are opened, larvae can be found inside. Here, you can see the orange, third instar, through the lesion (right). Photos by Ashley Dean.

The fields we confirmed larvae in this year had low infestation levels – we could only find a few plants with black lesions and there were less than five larvae inside. Make sure to check field edges for dead plants, wilting, and black lesions, then break the stem open to confirm that soybean gall midge larvae are inside. Infestations in new counties may be difficult to spot because of this low incidence or be confused with fungal pathogens.

There are no proven management tactics available for soybean gall midge at this time. Insecticides are likely ineffective because the larvae feed inside of the stem and are difficult to reach. We recommend monitoring for larvae during July and August, especially in soybean fields that have a border with a field where soybean was planted the previous year.

For more information on soybean gall midge, read this ICM encyclopedia article. If you are interested in real-time updates on soybean gall midge activity and distribution in 2023, join the Soybean Gall Midge Alert Network or the Iowa Pest Alert Network.

First detection scouting tips:

Midges overwinter in soybean fields and begin adult emergence in mid-June. They will seek out soybean to lay eggs but aren’t considered long-distance flyers. New field detections are almost always confirmed along the edge rows. If these plants are clean, do not bother sampling the field interior.

  • Start looking at the edge rows that are adjacent to a field that was soybean the previous growing season (likely now a cornfield).
  • In vegetative soybean, focus on finding wilted or stunted plants. Pull the plants and break open the stem just above the soil line to find feeding larvae.
  • Often surrounding plants will fill in the gaps of dead plants or get replaced by weeds.
  • In reproductive soybean, part the canopy and look for dark lesions on the stem just above the soil line. In some cases, infested plants become brittle and easily break off from the roots.
  • Later in the season, infested and dead plants can be held up by surrounding plants.

If you find soybean gall midge in a county not indicated as infested in Figure 1, reach out to your region's extension field agronomist or the authors for confirmation.

Category: Crop ProductionInsects and MitesTags: soybean gall midgescoutingdistributionAuthors: Ashley DeanErin HodgsonCrop(s): Soybean

Regional Update: August 8 - August 16, 2022

ICM Blog - Tue, 08/16/2022 - 15:38

While the story of the "haves" and "have nots" continues across the state, some areas in NW did finally get some much-needed rain early this week. And unfortunately, the Zearing area in Central Iowa also had some hail damage. Some of the observations or questions coming in from the field this last week have been on or have included: spider mites, new counties in Iowa found to have soybean gall midge, soybean aphids, tar spot, SDS, and potato leafhoppers. Read on for more specifics of what’s happening around the state.  

Northwest Iowa

Joel DeJong (Region 1): “A week ago, the northern part of the region I serve received a much needed rainfall. However, the driest part of the region missed most of that event. The good news, on Monday most of the area that was missed a week ago received an inch or better. For some fields along the western edge of the state it might be too late – in fact, several have been chopped for silage already. Most fields will still benefit greatly from this precipitation event. In the drier regions spider mite populations have been increasing. Cooler weather and moisture might help crash these populations; we hope. Along the Minnesota border and increase in soybean aphid populations has been reported. A reminder, if treating those pests’ insecticide pre-harvest intervals need to be considered, and once soybeans reach the R6 stage the chance of recovering your investment goes down considerably.”  

North Central Iowa

Angie Rieck-Hinz (Region 3): “ It continues to be the “haves” and “have nots” across the 8 counties I serve, at least in terms of rainfall.  Parts of Humboldt, Webster, Hamilton and Wright got some much-needed rain on Monday, August 15, although more is needed. Parts of southern Hardin County into northern Story County experienced a downburst with hail that caused significant crop damage around Zearing in a storm that passed through on Thursday, August 11th. Crop conditions are highly variable across the area. I am receiving more and more reports of tar spot in my northern counties where there has been significant more moisture, but the majority of photos shared with me still indicate low severity. However, there are some fields with a higher degree of severity so take some time to evaluate your hybrid ratings to make defensive choices for next year. I have also received scattered reports of aphids in corn. There are no treatment thresholds for aphids in corn, but this ICM article offers points to consider. Gray leaf spot and northern corn leaf blight are also present. Sudden death syndrome is starting to make an appearance in soybean fields.”

Recently found corn aphids in northern Iowa.  Photo courtesy of Dave Steen, Five Star Coop.

 Northeast Iowa

Josh Michel (Region 5): “Over the past week, most of NE Iowa received anywhere from 1 to 1.5 inches of rainfall, with isolated heavier amounts of 2 inches in parts of Allamakee, Clayton and Winneshiek counties. Most of the corn in NE Iowa is currently at R3 to R4. I continue to receive calls about corn rootworm and disease management as we’re seeing increased pressure of tar spot and gray leaf spot. Soybeans are mostly at R3 to R4, as pod are continuing to develop. Leaf defoliation and late-season waterhemp emergence continue to be the main issues. I’ve also heard of some SDS and soybean aphids starting to show up in a few areas. Most of oats have been harvested, and I’d expect any remaining fields to be harvested this week pending favorable weather. Alfalfa harvest continues across the region, as farmers continue to scout for grasshoppers and potato leafhoppers. Most of my field calls over the past week have consisted of alfalfa pests and scouting, soybean aphids and defoliation, small grains and forage management, weed management in pastures and CRP fields, and managing corn and soybean diseases.”

Central Iowa

Meaghan Anderson (Region 7): “Most of central Iowa received some much needed rain over the last week, but it didn’t come in large amounts (mostly <1”), so the crop stress and lack of moisture continues across much of this area. A small area in Story and Hardin counties received significant hail with some rainfall last Thursday afternoon and some crops in that area suffered significant leaf tissue loss, stalk bruising, and ear/pod bruising. We’ll have a hail meeting in Zearing, IA at 10 a.m. on August 17 to talk about the crop damage (see flyer: crop_damage_meeting_-_zearing.pdf). Corn is primarily in the dough (R4) growth stage and soybeans are primarily in the late R4 to early R5 growth stage across central Iowa. Twospotted spider mites, aphids, corn rootworm beetles, and grasshoppers are still familiar sights in corn fields, but disease pressure remains low. Twospotted spider mites are present in some soybean fields but the cooler temperatures and moisture should help keep them from spreading rapidly. Soybean gall midge was recently spotted in soybean in both Polk and Warren counties; these videos can help scouts determine what to look for. Crops are continuing to show stress from lack of moisture, especially in lighter soils, compacted soils, or areas where nitrogen loss was high earlier this spring; the recent rains will help but we could use some more to finish out these crops!”

Significant hail damage and defoliation to early R5 soybeans near Zearing. Photo courtesy of Meaghan Anderson.

East Central, Southeast, and South-Central Iowa

Rebecca Vittetoe (Region 8): “It’s the same song in EC Iowa when it comes to the "haves" and "have nots" with rainfall over the last week, with my more northern counties receiving more rain than my southern counties. Poweshiek, Marion, Mahaska, and Keokuk counties (or parts of them) are classified as a severe drought (D2) on the U.S. Drought Monitor. Corn is R4-R5 and a lot of soybeans fields are now at R5. Crop conditions are variable across the area. In the areas that have been catching rain, the crops look really good and in the drier areas things look tough. Additionally, in the drier areas, spider mites are more common, but hopefully the cooler conditions will help to slow them down. Other pests or diseases noted in fields this past week include corn aphids, soybean aphids (more my northern counties), corn rootworms, potato leafhoppers in alfalfa, tar spot, and late season weed escapes. Questions this past week have mainly been on corn rootworms, spider mites, late season weed escapes, and nitrate concerns for silage in the dry areas.”     

U.S. Drought Monitor Map. Source: https://droughtmonitor.unl.edu/CurrentMap/StateDroughtMonitor.aspx?IA.

Virgil Schmitt (Region 9): “Rainfall last week in the counties I cover was 0.5 inch or less except there was as much as 1.0 inch along the Highway 30 corridor. Areas roughly south of Highway 92 are listed as DO (abnormally dry) except that western Henry County and much of Lee County are listed as D1 (moderate drought) on the August 9 Drought Monitor. In general, temperatures during the last week in the counties I cover were one to three degrees below normal. Most corn is R4-R5 and looks good to excellent except for areas showing drought stress. There are low levels of gray leaf spot in some fields and tar spot can be found here and there. Most soybeans are at R4 and also look good to excellent except for areas showing drought stress. Again, disease levels are very low. Japanese beetles continue to be found in all of the counties I cover. Potato leafhoppers continue to be present in alfalfa and there are winged grasshopper adults in grassy areas. Phone calls, emails, and field visits last week mostly involved insect feeding on soybeans and waterhemp management in soybeans.”

Rainfall totals across the state from Aug. 9 - Aug. 15, 2022. Source: https://mrcc.purdue.edu/CLIMATE/Maps/stnMap_btd2.jsp.

Check out the map below to find your local ISU Extension field agronomist and find their contact information here!

Category: Crop ProductionTags: regional updateCornsoybeansspider mitesdroughtaphidsAuthor: Rebecca Vittetoe

ISU offers three fall field days

ICM Blog - Thu, 08/11/2022 - 13:00

You are invited to attend the upcoming field days that will be hosted at the outlying Iowa State University Research and Demonstration Farms this fall. These field days will feature the latest information on crop production and crop management practices. Below is a list of the upcoming field days that will take place in August and September and what topics will be featured at each field day. All field days are free and open to the public, but please check for registration details for meals.

August 24, 2022 - Northeast Research and Demonstration Farm (3321 290th St., Nashua, IA)

Registration for this event starts at 12:30 p.m. Field day activities start at 1:00 p.m. and continue until 4:30 p.m. The field day is free and open to the public. CCA credits will be offered. Pre-registration is not required.

Topics include:

  • Carbon science for carbon markets
    • Dr. Lisa Schulte Moore, professor of natural resource ecology and management
  • Corn rootworm resistance, management and the new RNAi technology
    • Erin Hodgson, extension entomologist 
    • Ashley Dean, education extension specialist
    • Bill Long, field agronomist with Pioneer
  • Cover crops and impact on water quality trials at the research farm
    • Dan Andersen, professor in Agriculture and Biosystems Engineering
  • Sudden death syndrome and other soybean diseases
    • Steve Harris, department chair in plant pathology, microbiology and entomology

Click here for more information on this field day.

September 8, 2022 - Northern Research and Demonstration Farm (310 S. Main St. Kanawha, IA)

Registration for this September 8th field day beings at 9 a.m. with the event kicking off at 9:30 a.m. Lunch will be served at 12:30. Please RSVP to the Wright County Extension Office at 515-532-3453 by September 2ndso we can include you for lunch. The field day is free and open to the public. CCA credits will be offered.  

Topics include:

  • Potassium and nitrogen interaction on corn grain yield
    • Antonio Mallarino, extension soil fertility specialist
  • White mold and Sudden Death Syndrome (SDS) management in soybeans (plus some corn diseases)
    • Daren Mueller, extension plant pathologist
  • Planting date impact on corn and soybean yields – a look at the long-term research studies at the Northern Research Farm
    • Mark Licht, cropping systems specialist  

Click here for more information on this field day.

September 8, 2022- Southeast Research and Demonstration Farm (3115 Louisa-Washington Rd, Crawfordsville, IA) 

Registration and lunch for this September 8 field day starts at noon. This event is free and open to all, but please RSVP by September 6 to help with a headcount for lunch. Please either RSVP online at https://go.iastate.edu/RWZOHU or by calling the Johnson County Extension office at 319-337-2145.

This event will celebrate a ribbon cutting for Research and Learning Center at the Southeast Research and Demonstration farm with an open house and celebration of the 35th anniversary of the research farm.

Ribbon Cutting Ceremony for new Research & Learning Center and Comments from Special Guests

  • Wendy Wintersteen, President, Iowa State University
  • John Lawrence, Vice President for Extension and Outreach, Iowa State University
  • Dan Robinson, Endowed Dean, College of Agriculture and Life Sciences
  • Jay Harmon, Associate Dean for Extension and Outreach, Director for Agriculture and Natural Resource Extension and Outreach
  • Kendall Lamkey, Chair, Agronomy Department
  • Steve Harris, Chair, Plant Pathology/Entomology/Microbiology Department

SEIARA 35 Year History and Research Farm Update

  • Tim Goode, Research Farms Manager
  • Cody Schneider, Southeast and Muscatine Island Research Farm Superintendent

Networking, dessert and informal field plot tours and discussion will follow the ribbon cutting

Click here for more information on this field day.

More information about these and other field days to be hosted at the ISU Research and Demonstration Farms can be found here.  We hope to see you at one of these events!

Category: Crop ProductionTags: fall field daycrop production and managementAuthors: Angie Rieck-HinzRebecca VittetoeTerry Basol

Dry conditions causing spider mite issues throughout Iowa

ICM Blog - Thu, 08/11/2022 - 09:16

Twospotted spider mites have been noted in fields across much of Iowa already this summer, as much of Iowa is in abnormal or extreme drought (D0-D3, US Drought Monitor). Scouting for spider mites in field crops is encouraged with prolonged drought. Twospotted spider mites can increase whenever temperatures are greater than 85°F, humidity is less than 90 percent, and moisture levels are low. These are ideal conditions for the twospotted spider mite and populations can increase very rapidly.

Spider mites can typically be found feeding on the bottom side of crop leaves, and they begin feeding at the bottom of the plant. Initial feeding looks like yellow or white spots (called stippling; Photo 1) on the leaves. Prolonged feeding will cause infested leaves to turn completely yellow, then brown, and eventually the leaf will die and fall from the plant. This is often mistaken for “firing” of the lower leaves during drought stress in corn. Webbing often is visible on the edges and underside of leaves and is an indication of prolonged colony feeding (Photo 2). Scout fields by looking for small mites that look like specks of dirt on the undersides of leaves, beginning at the bottom of the plant and working up.

Photo 1. Twospotted spider mite injury on soybean. Photo by Whitney Cranshaw, Colorado State University, Bugwood.org.

Photo 2. Heavy twospotted spider mite infestation on corn. Photo by Adam Sisson, Iowa State University.

Exact treatment thresholds for spider mites in corn and soybean do not exist. Instead, consider how long the field has been infested, mite density including eggs, mite location on the plant, moisture conditions and plant appearance. A general guideline for soybean is to treat between R1-R5 (i.e., beginning bloom through beginning seed set) when most plants have mites, and heavy stippling and leaf discoloration is apparent on lower leaves. Foliar insecticides are recommended in corn from R1-R4 (i.e., silking through dough stage) when most plants have mites at or around the ear leaf and 15-20 percent leaf discoloration. Several insecticides and miticides are labeled for spider mites in corn and soybean in Iowa. Refer to the spider mite encyclopedia article for more detailed scouting and management information.

In soybean, insecticidal control decisions should take into account whether soybean aphid is also present in the field. In many areas of the Midwest, soybean aphid has documented field-evolved resistance to bifenthrin, which is one of the only insecticide active ingredients available for twospotted spider mite. See the soybean aphid encyclopedia article for more information.

Category: Crop ProductionInsects and MitesTags: twospotted spider mitecorn pestssoybean pestsscoutingAuthors: Ashley DeanErin HodgsonCrop(s): CornSoybean


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