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Fall Armyworm Management Considerations in Alfalfa and Cover Crops

Fri, 09/17/2021 - 16:12

2021 has been an unprecedented year for fall armyworms, not just here in Iowa but other states as well. There have been many questions regarding how to manage fall armyworms in hayfields and cover crop fields. 

Here is some background that may help explain some later comments.

  • There are two strains of fall armyworms.
    • The moths of the corn strain fly in from Texas and the Mexican Gulf Coast. Their favorite targets are corn, sorghum, and cotton.
    • The moths of the rice strain fly in from Florida and the U.S. Gulf Coast. Their favorite targets are rice, alfalfa, millets, forage grasses (including many cover crops), and turf. So, we have the rice strain this year.
  • The Fall armyworms have a complete life cycle – egg, larva, pupa, adult (moth). This cycle repeats itself about every 30 days. It is heat driven, however. We had the first round in Lee and Des Moines Counties about 25 days prior to the events north of Highway 92, so the above-normal temperatures we had sped up the development a little. And as we cool down going into fall, the timeframe will be lengthened a few days.
  • Fall armyworms cannot overwinter here, so the first good freeze event will destroy them. Whether there will be a problem in another year literally depends on which way the wind blows.
  • Scout at sunrise or sunset. Fall armyworms tend to be nocturnal, so scouting at that time will give the best perspective of the current situation. If you are scouting in the middle of the day, you may need to look closer at the soil to see if they are present or not.

And now for the guidance:


  • If there is enough hay present to make a cutting worth harvesting, mow ASAP. We normally do not recommend cutting hay between the end of the first week in September and freeze down / winter dormancy (which is usually the last week of October) if the field is to be kept for hay the following year. However, the climatologists and meteorologists are very lockstep that this Fall will run 2 – 4 weeks behind schedule, so there should still be time for full recovery (full recharge of carbohydrates in the roots) from taking the crop now. The later the mowing, the less is the likelihood of a full recharge of carbohydrates before going into winter dormancy. Also, if the armyworm food source is eliminated (harvested), where will the larvae go for food? Adjacent forage fields, ditches, waterways, pastures, CRP, cover crops, and farmstead lawns are likely targets, so there may be a battle on that front.
  • If there is not enough hay to make a cutting worth harvesting (either because of recent harvesting or if there is nothing but stems left in the field) and the larvae are less than ¾ inch long and we are seeing more than 2-3 per square foot, spraying a pyrethroid insecticide (Warrior, Baythroid, etc.) should give a good kill and allow for good recovery of the alfalfa. If there are just stems left in the field, they do not need to be mowed off. Once light hits the crown, new shoots will be initiated.
  • If there is not enough hay to make a cutting worth harvesting and the larvae are over ¾ inch long, it is probably best to let Mother Nature take its course. Once the larvae are over ¾ inch long, they become harder to kill with an insecticide and they only have a few days left before pupating, turning to moths, and flying away to lay eggs elsewhere. Full grown larvae are about 1.5 inches long. At that point, they bury themselves in the ground, pupate, and then emerge as adults several days later. The adults will seek out lush growth and lay their eggs there, and the beat goes on until a killing frost destroys the entire population.

Cover Crops Fields

  • Do you spray? Where you may consider spraying is if you are planning on grazing or harvesting the cover crop for forage either this fall or next spring. With spraying, it’s important to consider the size of the larvae. Follow the recommendations above regarding the size of the larvae and the threshold.
  • For cover crop fields with extensive damage and that have been literally chewed to the ground, the question becomes will the cover crop come back? The growing point of cereal grains would still be below the ground, especially if the field was drilled, as the growing point doesn’t move above the soil surface until it reaches the jointing stage, which occurs in the spring. This is good news because it means the plants will continue to grow. However, as long as armyworms are still present in the field they will continue to eat off the new growth. Stand loss may be affected by how much regrowth there is before winter dormancy is induced.
  • Read more on fall armyworms and cover crops in this ICM Blog.
Category: Insects and MitesTags: fall armywormscover cropsforagealfalfaAuthor: Virgil SchmittCrop(s): Biomass and Forage

Corn drydown and stalk quality

Thu, 09/16/2021 - 12:21

As corn has quickly reached maturity, the next hurdle of the 2021 growing season is harvest. Stalk quality will be a concern for fields across that state that experienced the stress of too much or not enough moisture. Alison Robertson recently wrote an article about stalk rots that is very good. I too suspect because of the stresses this year; stalk integrity will be compromised whether it be from stalk rots or simply because the plant cannibalized itself to fill out the ear as best it could.

Next steps are to get out into the field to conduct a pinch/push test. Observe how well the ears are hanging on the stalk. And get an idea for what the grain moisture and drydown potential are.

Corn grain drydown from physiological maturity to about 23% is nearly constant and is only minimally affected by air temperature and relative humidity. However, below 23% grain drydown can be influenced greatly by both air temperature and relative humidity. Sotirios Archontoulis and I developed a Corn Drydown Calculator that with minimal input of location and initial date and grain moisture can provide some estimation of how long it will take to reach your target harvest moisture.

This year may not be the year to wait until grain gets to 15% before harvesting. The longer corn stalks are left standing the greater the possibility for lodging and ear droppage to occur. Lodging, ear droppage, and header kernel loss are commonly greater the longer corn is left standing in the field and the drier corn is at harvest.

Use field scouting to assign a ‘harvest order’ to your corn fields to minimize the potential for mounting field losses.

Category: Crop ProductionTags: Corndrydownstalk integrityharvestAuthor: Mark LichtCrop(s): Corn

Power Line Safety for Harvest

Thu, 09/16/2021 - 10:05

Safety should always be at the forefront of your farming operations, and harvest is no different. When operating large equipment such as combines and grain carts, overhead power lines pose an increased risk to farm safety. An average of 62 people each year are electrocuted when their farm machinery contacts a power line.

To avoid potential incidents on your farm operation, follow these tips and those in the video below. ISU Digital Ag and ISU Extension and Outreach wish you a safe and productive harvest season. 

  1. Always fold in the auger on your grain cart or combine when it is not in use.
  2. Maintain a minimum of 10 feet in all directions (including above) between your machine and the power lines.
  3. Scout your fields for potential risks before harvesting, including low power lines or poles in the path of your equipment. Take this time to also identify the power company that manages the area so you can take note of who to call in case of an emergency.
  4. Overhead power lines should be at least 18 feet from the ground. Know which of your machines run the risk of touching a line, and take steps to avoid it. If you see any sagging or damaged power lines, contact your power company immediately.


Category: Equipment and MachineryTags: Digital Agfarm safetyharvest 2021harvest safetyelectrical safetyAuthors: Ben CovingtonRyan W BergmanVideo: 

Mixed bag in beans

Thu, 09/16/2021 - 07:52

I got invited to SERF (ISU Southeastern Research Farm) field day last week to highlight corn rootworm management. I was easily distracted when it wasn't my stop and started walking around soybean plots looking for insects. [this is a common occurrence with entomologists!] Soybean was in various stages of senescence around the farm as you could imagine with multiple maturity groups used for research projects. I was surprised by the variety of insects still present the first week of September. Of course, insects feeding directly on the maturing pods are of greatest concern during R6-R8 (e.g., bean leaf beetle, grasshopper, stink bugs). Highlights of insects I could find are included in a photo mashup below. 

Left-to-right, top-to-bottom: Japanese beetle, bean leaf beetle, grasshopper, stink bug, blister beetle, soybean aphid.

Category: Crop ProductionInsects and MitesTags: SoybeanpestscoutingAuthor: Erin HodgsonCrop(s): Soybean

Regional Update: Sept. 15, 2021

Wed, 09/15/2021 - 09:50

While the rains the end of August have helped to improve the dry conditions some across the state, the rains also brought along some strong winds and hail that caused some significant crop damage in parts of NE, EC, and SE Iowa by flattening cornfields and causing lodging in soybeans. Additionally, parts of NE Iowa also delt with some flooding. Common observations made in fields across the state include stalk rots and stalk integrity issues in corn and fall armyworms causing havoc in pastures and hayfields (and lawns). Read on for more specifics on what's happening in fields across the state.

Northwest Iowa

Gentry Sorenson (Region 2): “Corn and Soybeans are moving toward maturity. Some earlier maturity soybeans have dropped leaves and are close to harvest while others are in the early stages of dropping leaves. In soybeans SDS has been identified in a few fields, I also had phone calls regarding white mold. A few isolated cornfields have had end rows taken off or areas of fields harvested. Stalk quality has been a concern, I have seen stalk rots in the field as well as some root lodging. It will be important to check your fields to understand the standability of your corn as well as understand if any stalk rots are in your field to prioritize harvest over the coming weeks. Field calls have been about soybean disease and standability of corn.”

Starting to see more stalk rots and stanbilibty issues in corn. Make sure to check your fields and priortize which fields to harvest first. Photo courtesy of Rebecca Vittetoe.

Northeast Iowa

Josh Michel (Region 5): “Many areas in NE Iowa received significant crop damage from recent severe weather events that occurred on August 24 and again on August 27-28. While the most severe crop damage was isolated to areas in Buchanan and Fayette counties, crop damage had occurred to some degree in Allamakee, Clayton, Delaware, Dubuque, and Winneshiek counties as well. Since those weather events that came through, most of NE Iowa has remained relatively dry. Scattered light rain showers have only delivered 0.25-0.50 inches of rainfall over the past two weeks. While dry conditions will help facilitate an earlier harvest, we will need some rainfall to help forages get some needed growth before a killing frost later this fall. Grain harvest has started in some areas as moisture levels continue to fall, while the last alfalfa cuttings for the season are finishing up. Recent field calls have centered mostly around down corn, specifically what are the options and considerations to keep in mind with harvesting corn for silage or grain, and what concerns there might be about grain quality and storage. Other field calls have included: corn rootworm management, forage management and new forage seedings, fall weed management, and cover crop considerations.”

The stroms that rolled through NE Iowa late in August had some strong winds that flattened many cornfields across the area. Photo courtesy of Josh Michel.

Central Iowa

Meaghan Anderson (Region7): “Harvest has started in earnest in central Iowa and is coming quickly for anyone who hasn’t started yet. Much of the corn is mature and hopefully drying down well with the warm days and breezes lately. I’ve been hearing of moistures anywhere from the upper teens to the upper 20s and yield reports have been remarkable so far. I continue to receive phone calls and notice issues with standability in corn, so it is still a good idea to prioritize fields for harvest based on their stalk integrity. More soybeans are turning each day and a few fields have been harvested in central Iowa so far. Standability issues have been apparent in some soybean fields as well, with lanky beans and the rainfall we received in the latter half of August. We’ve got some good reference information on combine adjustments for harvesting lodged corn and MSU has a great reference on harvesting lodged soybeans.”

Most of the corn in central Iowa has reached black layer or is getting pretty close to reaching black layer. Photo courtesy of Meaghan Anderson.

East Central, Southeast, and South Central Iowa  

Rebecca Vittetoe (Region 8): “While we got some much-needed rain the end of August, but with that rain also come some wind and hail. A good portion of Keokuk County and parts of Mahaska and Poweshiek counties had some storm damage with downed and flattened corn, lodged soybeans, and some hail damage as well. Harvest has begun in EC Iowa, with corn silage harvest starting a couple weeks ago and within the last week folks have started harvesting some corn and soybean fields. Major concerns coming from the field include stalk rot and stalk integrity concerns in corn, tar spot becoming more apparent, and fall armyworms in pastures and hayfields. Take time to assess corn fields for stalk rots and if you are seeing more than 10% of the plants in the field with stalk rots, plan to harvest that field earlier. Also, be sure to check pastures and hayfields for fall armyworms.”

Scout pasture and hayfields for fall armyworms. They tend to be more active first thing in the morning or at the end of the day. You can often find them haning out by the soil during the day, like the ones in the picture. Photo courtesy of Rebecca Vittetoe.

Virgil Schmitt (Region 9): “Rainfall during the last three weeks in the counties I cover was generally one to three inches. In general, temperatures during the last week in the counties I cover were two to three degrees above normal. Corn is generally late R5 to R6 and soybeans are generally late R7 to R8. Corn silage is being harvested and third cutting of hay is wrapping up.  Calls and farm visits last three weeks mostly involved weed management identification and management and fall armyworms.”

Rainfall totals across the state from August 23 through Sept. 13, 2021. Source: https://mrcc.illinois.edu/CLIMATE/Maps/stnMap_btd2.jsp

Clarabell Knapp (Region 11): “ The past few weeks in our area have been full of silage harvest and wrapping up third cutting in hay fields. We have continued to receive timely rains and have totaled anywhere from 0.5 inchto nearly 2 inches. One of the storm systems produced stronger winds around the Pekin/Packwood area, where some fields experienced crop damage. Many corn fields are in the R6 stage and some growers have begun harvesting high moisture corn in the last few days. Soybean fields are steadily turning color and are typically found in the R7 stage. There have been a lot of questions recently regarding fall armyworms in hay and alfalfa fields and what control methods are available. A great resource to answer these questions and to provide more details can be found here."

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

Category: Crop ProductionTags: crop updateharvestarmywormsstalk rotsend of the seasonAuthor: Rebecca Vittetoe

End of season thoughts: stalk rot, ear rot and tar spot

Tue, 09/14/2021 - 07:14

As the 2021 growing season comes to a close, what should you be thinking about in terms of corn disease and how that might impact your harvest plans?


Crown and stalk rots

Have you noticed scattered, individual plants in a field turning brown, appearing to have reached physiological maturity? Chances are these “ghost plants” have crown and/or stalk rot.  Using a knife to split the plants from the ear down to the crown will provide a diagnosis. Plants with crown rot will, as the name implies, have a discolored, rooted crown (Figure 1). Plants with stalk rot will have shredded, and/or discolored pith in the internodes, and discolored nodes (Figure 2). Pink to red discoloration may indicate Gibberella or Fusarium species as the cause. Dark discoloration could be anthracnose, and peppering (tiny black spherical sclerotia scattered throughout the pith), charcoal rot. While not much can be done to manage the disease now, taking good field notes is important to plan for subsequent years.

Crown and stalk rots can compromise standability as infected plants are more prone to lodging. Two simple tests for lodging potential are the ‘push’ and ‘pinch’ tests that you can read more about here. Fields in which more than 10 percent of the plants have crown or stalk rot should be scheduled for an early harvest.

Figure 1.  Characteristic symptoms of crown rot (left); healthy plant (right).


As a side note, I have also started to notice anthracnose top dieback: random, scattered plants that are dying from the top. Plants with top dieback usually develop stalk rot.  Thus, if you notice fields with top dieback symptoms, it’s a good idea to scout these for stalk rot too.


Ear rots

Although I have not noticed any ear rots in my trials or heard reports of ear rots, I suspect I will start to soon. I have noticed a lot of insect damage to kernels, which can lead to ear rots. Additionally, while the precipitation events that have occurred across most of the state through August have provided much needed moisture for the crop, they also provide a more favorable environment for fungal pathogens that cause various diseases of corn, including ear rot. It is important to scout your fields for ear rot because some fungi that cause ear rots produce mycotoxins. Similar to crown and stalk rot, if more than 10 percent of the plants have ear rot, schedule an early harvest, and get the grain dried and cooled as quickly as possible to prevent further fungal growth and mycotoxin production. Always store grain harvested from a field with ear rot in a separate bin from grain from healthy fields to prevent more grain from being contaminated.

The Crop Protection Network has an excellent publication on identifying ear rots.


Update on tar spot

I continue to hear reports of tar spot in Iowa. For the most part, the disease remains at pretty low levels, but there have been some fields along the eastern border of Iowa where the disease has become a concern. A fungicide application at around silking appears to have done a good job at reducing disease in some fields. Plants with high levels of tar spot die prematurely and lodging can be an issue. While it’s too late to do anything for tar spot this year, now is a good time to get out and make note if you see hybrid differences, which can help you plan for next year and also help you prioritize fields for harvest.






Category: Plant DiseasesTags: Anthracnose stalk rot; fungicideAuthor: Alison RobertsonCrop(s): Corn

Tips on Field Mapping with Aerial Imagery

Thu, 09/09/2021 - 11:34

As harvest starts to ramp up across Iowa, many people will be evaluating their crop scouting activities from 2021 and starting to make plans for 2022. In a previous article, we outlined options for capturing imagery of your fields to aid in scouting and making management decisions. Fall can be a great time to capture imagery to understand crop dry down, late season weed pressure and crop lodging. As you consider remaining imagery needs for 2021 and make plans for 2022, there are three characteristics of imagery you should understand:  

Figure 1. At this mid-range level of resolution of 20 inches in the top image, it’s possible to pick out row to row variation, but stand counts would still not be possible. At the 2-inch resolution on the bottom, it’s possible to see individual plant leaves later in the season and would provide the ability to do stand counts earlier in the season.

  1. Image Resolution
  2. Image Timing
  3. Image Type or Spectral Bands Captures

Image Resolution

Image resolution is the measure of the land area represented in a single pixel of your image. An image for a low-altitude UAV flight might be around 1 square inch per pixel, while a satellite image may be 6 square feet per pixel. With both UAVs and manned aircraft, resolution depends on the camera used and the flight altitude. Flying lower will increase resolution, but will also increase flight time and require a number of passes across the field to complete a map.

The level of resolution you need depends on your intended use for the imagery. To simply document drainage issues and ponding, satellite imagery may be suitable. However, if you’re looking to conduct plant stand counts or assess emergence issues, higher resolution images (likely from a UAV) will be necessary.


Image Timing

Timing your imagery capture with the weather is key to getting high quality images. However, it’s just as important to consider the growth stage of your crop when deciding when to conduct a flight. Flying too early in the season when not much plant growth has been established above the soil can result in an image that shows mostly soil. Flying too late can often hinder your ability to identify issues with planting, emergence and early season development. Figures 2, 3, 4, and 5 show aerial images taken of the same field several weeks apart. Note: These images are from 2019, which came with a wet spring and delayed planting in this field. The amount of soil visible in these images is not likely to be seen in June in an average year.  

Figure 2. This image was likely taken too early to assess crop emergence and vigor differences. This early imagery can be beneficial to understand water flow and pothole areas of a field. Some users have been able to map tile lines off this type of early imagery when the fields are saturated by spring rain.

Figure 3. Crop growth at this point is far enough along to see visual differences in crop color and vigor across the field. The impact of soil compaction from spring equipment passes is visible around many of the drowned-out areas of the field. Headland traffic from in-season sidedressing and spraying is also very visible.

Figure 4. By this point of the season the crop is far enough developed many of the early season crop vigor differences are difficult to detect. However, an area of tile work in the lower left area of the field is very evident in this image. Some compaction from traffic is visible across the field, but more difficult to see the impact of individual tires on a row.

Figure 5. Later season imagery can be useful for assessing variability in crop dry down. Some areas in this image are starting to dry down (center area of the image). Drowned out areas are still green with weeds at this stage. Some areas of around the tile work and drown out areas still appear yellow due to reduced crop vigor.


Image Type or Spectral Bands Captures

A popular image type for assessing fields is a NDVI (normalized difference vegetative index). NDVI utilizes an NIR (near infrared) image to generate the NDVI map. Time images shown in Figure 6 display the raw NIR image on top and the resulting NDVI image on the bottom. The near-infrared light bands can often display different characteristics than traditional RGB color images. The NDVI map highlights these differences by displaying them with varying colors.

Figure 6. A comparison of the same field captured using NIR and NDVI imagery.

Other indexes are also available and require different inputs in terms of light wavelength recorded by the camera. A VARI (visible atmospherically resistant index) will often look similar to NDVI, but uses an RGB photo input and emphasizes different crop characteristics.

Figure 7. A comparison of the same field captured using RGB and VARI imagery.

These indexes often look and are viewed similarly to a combine yield map. It’s important to understand the color variations and how they were assigned to show differences in crop vigor. Indexes are a way to categorize and differentiate data points to make differences easier to identify. These indexes often may display areas of lower or higher yield, but perceived poorer areas of a field in an image may still yield as well as other areas. The image doesn’t always predict a yield difference.

When deciding to include aerial imagery as part of your management plan, it’s important to understand not only the process of capturing images, but the options and adjustments that will affect the quality of your image. Take time to evaluate your crop scouting needs and take these characteristics into account before heading to the field or scheduling a flight.


Category: Equipment and MachineryTags: Digital Agaerial imageryUnmanned Aerial Systemdrone usageUAVsAuthors: Ryan W BergmanChris Murphy

Tips for Harvesting Test Plots and Trials

Tue, 09/07/2021 - 15:30

Figure 1. Yield sensors damaged by dirt or other debris must be replaced and data collected with damaged sensors should be removed from analysis.

With harvest quickly approaching, it’s time to make sure your combine is prepped and ready for the field. This article published in fall of 2020 has some good tips for calibrating your yield monitor to ensure high quality yield data. If you are going to harvest test plots or other strip trials with your combine, there are some additional steps you should consider to ensure high quality data from test plots.

Evaluate the Status of your Yield Monitor Components

Many growers harvested downed crops because of the 2020 derecho. While we recommend inspecting your combine and its yield monitoring components every year, it may especially important this year for many. Debris in fields in 2020 (like metal from buildings, wood, etc.) as well as crops with more dirt due to being downed may have prematurely worn components on your machine and could cause your yield monitor accuracy to be impacted.

Inspecting critical components like the impact plate, clean grain elevator paddles and chain tension as well as the crop moisture sensor to ensure they are in good condition and ready for harvest will help produce high quality yield data. It’s important to remember that any adjustments made to the clean grain elevator chain tension will impact how crop hits the yield monitor impact sensor and is cause to recalibrate the yield monitoring system.

Figure 2. As corn moisture increased, yield monitor accuracy decreased. This is a primary driver for the importance of recalibrating yield monitors.

Calibrate the Yield Monitoring System

Ensuring the combine has a good multi-point calibration is a key first step to ensuring accuracy. Make sure the speed and yield of the crop being harvested in your trial area is similar to at least one point included in your multi-point calibration. This ensures the flow rate the machine will be operating at while harvesting your trial has a similar, scale verified calibration point. It’s also important to do multi-point calibrations with weights from a well-calibrated grain cart or weigh wagon. 

Crop moisture is often the biggest culprit of errors in yield monitoring systems. Ensure the multi-point calibration being used was developed with crop of similar moisture. Moisture differences of as little as 2.5% could cause yield measurement errors of up to five percent. For step-by-step information on calibrating your combine’s yield monitor, the Iowa State University’s Digital Ag team provides an online interactive monitor guide

Understand the crop flow delays within your machine

If harvesting continually through a strip trial or check block in a field, it’s important to understand delays in crop flow that are inherent with combine harvesters. On average, it takes about 13 seconds for grain to get from the combine head to the mass flow sensor. This delay depends on a variety of factors, such as header width, ground speed and the type of crop being harvested. Most commercial yield monitors attempt to correct for some of this delay in the display. By verifying that your GPS offsets and other machine parameters are properly set up, you can ensure the display will correct for this to the best of its ability. Failure to properly set up your display could result in the test block or strip trial not lining up correctly with other data sets, making analysis difficult.

Figure 3. As the combine continues to travel through the field, large amounts of grain are averaged to create a single data point. This increases with harvest speed. With a 40-foot corn head traveling at 2.5 miles per hour, grain from about 19 feet of forward travel distance is being merged to create a single data point. As speed increases to 4.5 miles per hour, the distance increases to 34 feet of travel.

It’s important to also understand that crop from the outside of the head takes longer to reach the feeder house than rows near the center of the head. This results in crop being merged along the forward travel distance of the combine. This distance changes based on header width and travel speed, shown in Figure 3. Consider this when harvesting field trials and plots. If continually harvesting through multiple plots, it will take a significant distance for all the grain from the first plot to pass by the yield sensor before you are completely measuring only grain from the second plot. When harvesting field trials, it’s recommended that a plot length be no less than 100 feet to account for this delay and collect the most accurate data. For more information on how this can affect yield data, see our spring article on setting up field trials.


Be wary of data from crop damaged fields

If harvesting crops from a field with wind or other damage that impacts your harvesting speed, caution must be taken when analyzing data. If your combine is speeding up and slowing down as it travels through a field, or for different crop varieties that have differing levels of damage, the associated yield data could be biased if machine flow rates are outside the flow rates you calibrated for. Additionally, if fields have extreme damage, any trial data from that field may not be accurate or representative of a typical year. You will have to decide whether to include it in any trial analysis, as well as whether to include the field as a whole in your continuing multi-year yield analysis.

The information discussed above is in regards to harvesting continuously through field trails or plots. The best way to get absolute data from test strips is to harvest all the grain from the test pass and weigh it in a calibrated grain cart or weigh wagon. Accurate yield data can be highly valuable for improving crop management and input decisions on your operation, but it needs to be a year-long practice to reap the full benefits. As new technology and automation tools continue to develop and become more hands-off for operators, it’s important to continue paying close attention to your data collection systems to quickly address any issues and ensure useful and insightful analytics. Ask for help as needed from local extension professionals or others in ag retail who can help you prepare in a way that results in high quality data.

Category: Crop ProductionTags: Digital Agfield testscrop testingfield plotssmall-plot experimentscombine harvesting tipsharvest 2021Authors: Ryan W BergmanMatt DarrLevi Powell

2021 Palmer amaranth Tour: Old Habits Die Hard

Tue, 09/07/2021 - 14:25

Although I am retired, I still am passionate about weeds and decided to continue my Labor Day Tour of the first known infestations of Palmer amaranth in Iowa. I started this ‘survey’ in 2014, links to earlier reports are found at the end of this article. My efforts do not involve a systematic sampling of Palmer amaranth infestations at these sites, but rather casual ‘hit and run’ observations. All but one of the sites involve less than 2 acres, so it is relatively easy to subjectively evaluate the prevalence of Palmer and observe changes in numbers from year to year.

Harrison County: This is the second straight year that I did not find any Palmer on the field edge or the adjacent roadside of the first field where Palmer was found in Iowa. However, the infestation in the alfalfa field across the road seemed greater than in 2020. A concern with this location is that transport of alfalfa could introduce seed to new areas. Grade: B

Pottawattamie County: In 2019 I was made aware of several ag fields inside an industrial area of Council Bluffs that had heavy Palmer infestations. This year the field I have followed had been left fallow and was dominated by annual weeds (the first step of old field succession). Marestail/horseweed was the most prevalent species, favored by its early germination, but Palmer amaranth, common ragweed and annual sunflower were holding their own. Ironically, marestail was suppressing Palmer amaranth better than the weed management program the previous two years since the Palmer population was lower this year than in 2019 and 2020. Grade: C-

Mills County: By happenstance, in 2019 I discovered a roadside infestation about ½ mile in length between I-29 and a large soybean processing facility. I suspect Palmer seed dropped from trucks bringing grain from Nebraska or other states with more significant Palmer amaranth infestations. The past two years there was a 6 ft wide strip of Palmer immediately adjacent to the road, but this year this area was solid annual grass weeds (foxtail, fall panicum, crabgrass). I suspect the county used multiple applications of a synthetic auxin herbicide (HG 4) to manage the Palmer. Grade: A+

Fremont County:  There seemed to be more Palmer escapes in the managed perennial sod (regular mowing) adjacent to the small crop field where Palmer was initially found. However, there was a large reduction in plants across the road in an area that in previous years had a sweet corn patch, but this year was not planted and left ‘to the weeds’. Unlike Harrison County the area appeared to have been mowed regularly. In addition, I didn’t find Palmer in roadsides about ½ mile from the initial infestation where it had been in previous years. Grade: B

Page County: This site had some major construction over the summer, eliminating some of the areas where Palmer was found previously. However, there were small patches of Palmer growing amongst other native and naturalized weeds in unmanaged areas of the commercial ag site. Grade: C

Summary:  As in previous years, I saw no evidence that Palmer amaranth is increasing in prevalence at these sites nor does it seem to be spreading. However, it continues to be frustrating to see the persons responsible for managing these areas aren’t going the ‘extra mile’ to prevent seed production and eradicate the newly introduced weed. They are missing the opportunity for ‘early detection and eradication’. Eventually Palmer amaranth will adapt to Iowa conditions and be much more difficult to manage.

Trip highlights:  I always enjoy the opportunity to jump across the Missouri River and have lunch with my daughter, a zookeeper at the Henry Doorly Zoo in Omaha.  But weed-wise, the highlight was finding several patches of Johnsongrass when driving north out of Hamburg. When I first came to Iowa, there were no known permanent infestations of this perennial weed in Iowa. Although infestations had been found, they usually died out after a couple years due to cold temperatures lethal to the rhizomes.

Previous tour blogs:


Category: WeedsTags: palmer amaranthLabor Day TourAuthor: Bob Hartzler

Yield checks Using the Yield Component Method

Mon, 09/06/2021 - 21:12

Anytime after R3 (milk stage) has traditionally been a great time to do yield checks in corn. After R3, kernel abortion is less likely and plant stress will result in reduced kernel size or fill rather than kernel loss. In addition to performing a yield check, 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. My colleague Patrick Hatting, Farm Management Specialist for central Iowa, and I performed yield checks in several Polk County corn fields in mid-August. See the details below.

Patrick and I visited 9 corn fields in Polk County on August 18 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 – estimates. The average yield of our 9 estimates using this method was 217 bu/ac in Polk County, but I’ll be very pleasantly surprised if the average corn yield approaches that number! Be sure to note areas where yield estimates are made in order to make comparisons after combines have run; you may even 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).

Category: Crop ProductionTags: corn yieldestimating yieldscorn grain yieldsexpected yieldsAuthor: Meaghan AndersonCrop(s): Corn

Tips for Harvesting Downed and Wind-Damaged Corn

Wed, 09/01/2021 - 09:47

Figure 1. Lodged crop near Plainfield, IA. Photo Credit: Josh Michel, ISU Extension Field Agronomist

With the recent storms rolling through northern Iowa, many growers are experiencing field conditions similar to those seen across the state after the 2020 derecho. To help ensure a safe and productive harvest, we’ve rounded up some tips and information that were developed after the derecho last fall for harvesting lodged and downed corn. While the damage from recent storms is not as widespread as last August’s derecho, some of the impacts to crops are very similar.

While you may be experiencing some of the same difficulties producers saw in 2020, a few key differences in current conditions may mean a slightly better situation this fall compared to last year. First, most of the damaged corn this year was closer to physiological maturity. This should mitigate some of the concerns seen in 2020 about how to deal with completely lodged crops that were still actively growing. Second, some of the reports we have seen also indicate that the crop is lodged further up the stalk (18 to 24 inches off the ground) compared with 2020, when much of the crop was completely flattened and lodged at the soil surface. This should make the crop easier to feed into the combine head and result in lower losses than if the crop was completely lodged at the soil surface.

Combine Adjustments for Harvesting Lodged Corn

This article outlines a list of operational changes that may increase combine performance in severely damaged fields. Additional details and guidance can be found in the reference articles at the bottom of the page.

VIDEO: Tips for Harvesting Downed Corn

In this 3-minute video, Dr. Matt Darr and Ben Covington with ISU Digital Ag share their tips for harvesting downed corn as well as resources that are available statewide to help growers manage a difficult harvest.

Category: Crop ProductionTags: corn damagehigh wind damagederechocombine harvesting tipsharvest challengesharvest 2020Author: Ryan W BergmanCrop(s): CornVideo: 

Upcoming Fall Field Days

Tue, 08/31/2021 - 22:27

Mark your calendars for our upcoming fall field days. Below is a list of the upcoming field days that will take place in early September and topics featured at each field day. All field days are free and open to the public. We hope you can join us!

Sept. 7, 2021 – Annual Forage Field Day hosted at Wells Dairy Farm (14658 252 St. Milton, IA)

This Sept. 7th field day will begin at 5:30 p.m. with a meal. Topics to be discussed during the field day include:

  • Agronomic considerations with annual forages
    Clarabell Knapp and Rebecca Vittetoe, ISU Extension and Outreach field agronomists
  • Utilizing annual forages in livestock operations
    ISU Extension and Outreach beef specialist Patrick Wall
  • A farmer’s perspective and experiences with using annual forages
    Jason Wells, Van Buren County farmer

The field day will include a tour looking at the annual forages being utilized on the Wells Dairy Farm. If you plan to attend, please RSVP to the Van Buren County Extension Office by noon on Sept. 7 by either calling the office at 319-293-3039 or emailing nancarr@iastate.edu.

Click here for more information, including directions to the farm.

Sept. 8, 2021 – Strip-till Field Day hosted at the Agriculture Engineering and Agronomy Research Farm (1308 U Ave., Boone, IA)

Registration for this Sept. 8th field day starts at 9 a.m. with the event kicking off at 9:30 a.m. and a complimentary lunch to follow the event at noon.

Topics to be featured include:

  • Welcome and 2021 research farm update
    Michael Fiscus, Agricultural Engineering and Agronomy Research Farm Superintendent and Meaghan Anderson ISU Extension field agronomist
  • Strip-till considerations for farmers
    Matt Darr, professor in agricultural and biosystems engineering at Iowa State
  • Considerations for reduced tillage and carbon markets
    Chad Hart, professor in economics and extension grain markets specialist at Iowa State University
  • Equipment and new technology demonstrations (will include several equipment manufacturers like Soil Warrior, Lynx Ag, Orthman, and Kuhn Krause)

Those who attend can qualify for two soil and water CCA continuing education units. RSVP to Meaghan Anderson, ISU Extension field agronomist by Friday, Sept. 3, to assure your spot and a complimentary lunch, at mjanders@iastate.edu or 319-331-0058.

For more information on this field day, click here.

Sept. 9, 2021 – Northern Research and Demonstration Farm Fall Field Day (1040 James Ave., Kanawha, IA)

Registration for this Sept. 9th field day will start at 9:00 a.m. and will feature the following topics as well as a wagon tour of the research farm:

  • Research Farm and Growing Season Updates
    Matt Schnabel, Northern Research Farm Superintendent
  • Dry conditions impact on soil sampling and corn stalk nitrate test results
    Antonio Mallarino, professor in agronomy and extension specialist at Iowa State
  • Growing season impacts on crop yields and harvest considerations
    Mark Licht, assistant professor in agronomy and cropping systems specialist at Iowa State
  • Efficacy of 2021 weed control and weed control thoughts for 2022
    Angie Rieck-Hinz and Gentry Sorenson, ISU Extension field agronomists
  • Carbon markets: The Wild West
    Chad Hart, professor in economics and extension grain markets specialist at Iowa State

A noon lunch will be available, at which time Hart will speak. The field day is free, open to the public and includes complimentary refreshments and lunch. A total of 2.5 CCA credits are available. Please register by contacting the ISU Extension and Outreach Wright County Office at 515-532-3453. More information on this field day can be found here.

Sept. 9, 2021 – Southeast Research and Demonstration Farm Fall Field Day (3115 Louisa-Washington Rd, Crawfordsville, IA)

Registration for this Sept. 9th field day starts at 1 p.m. with the field day kicking off at 1:30 p.m. Certified crop advisor credits will be available (1 PM and 0.5 SW). Topics to be featured include:

  • Research Farm and Association Updates
    Cody Schneider, Southeast Research and Demonstration Farm manager and Duane Jordan, past president/board member of the Southeast Iowa Agricultural Research Association
  • Utilizing Tile Drainage to Increase Productivity
    Matt Helmers, professor and agricultural engineering specialist with ISU Extension and Outreach
  • Corn Rootworm Management Strategies and Demo
    Erin Hodgson, professor in entomology and extension specialist in entomology at Iowa State University
  • Integrated Weed Management Strategies in Soybeans
    Prashant Jha, associate professor and extension weeds specialist at Iowa State

This field day is free and open to the public. No RSVP is needed and refreshments will be available. Click here for more information on this field day.

Sept. 15, 2021 - Western Research and Demonstration Farm Fall Field Day (36515 Hwy E34, Castana, IA)

The Western Iowa Research and Demonstration Farm will be hosting a fall field day on Sept. 15 from 10:30 a.m. to 3:00 p.m. The Western Iowa Experimental Associaiton will be celebrating its 75th Anniversary during this field day. 

The field day will highlight current and historic agricultural research important to western Iowa agricultural interests.  A steak  lunch provided by Tyson Fresh Meats and the Monona County Cattlemen will be served at noon.  A brief keynote address will be provided by Dr. Jay Harmon, Iowa State University Director of Agriculture and Natural Resources Extension. 

Topics to be cover after lunch include:

  • Corn and soybean genetic demonstration plots
  • Technology in agriculture including drones and GIS tools
  • Livestock production
  • Soil demonstration pit
  • Equipment used through the decades and more.

For more information on this field day contact the Western Experimental Association Research Farm Manager, Chris Beedle at 712-420-2460.

Category: Crop ProductionTags: field daysSERFNorthern Iowa Research Farmannual foragesWestern Iowa Research FarmAuthors: Rebecca VittetoeMeaghan AndersonAngie Rieck-HinzClarabell KnappJoel DeJong

Regional Update: August 9 to August 24, 2021

Tue, 08/24/2021 - 22:38

The drier and warm conditions have really pushed crops along across the state. In addition to the drought concerns and issues related to the drought, other common observations made in fields across the state include more sightings of tar spot, sudden death syndrome and/or brown stem rot in soybeans, and corn rootworms. Read on for more specifics on what’s happening in fields across the state.  

Northwest Iowa

Joel DeJong (Region 1): “There are definitely “haves” and “have nots” around NW Iowa. Some areas aren’t coming close to getting the water needed to finish this crop, in fact some are finishing prematurely now. At the same time, fields ten miles away might have received 5+ inches of rain more than these stressed neighborhoods and look great. Silage harvest started early last week, of course on some of the poorer fields. Estimated yield reports for at least some of those fields was quite low. Silage harvest on better fields began in some areas this week, but others are still too wet to chop. Soybeans in the really dry areas were actually wilting during the daytime last week, while in other areas they looked great, too. However, there has been more white mold showing up recently in parts of those areas that received good rainfall during the first half of July. Sudden death syndrome (SDS) has been observed at times, and spider mites continue to cause some damage occasionally. I had the chance to visit the area that was hailed out in late June in Plymouth County, and found corn a week post-tassel, and soybeans fully flowered (R2). These acres will certainly need quite a bit more time. A reminder to all producers, as we reach maturity in these cornfields, you will really need to evaluate for standability and prioritize your harvest!”

Corn field that has missed most of the rains and is finishing prematurely. Photo courtesy of Rebecca Vittetoe.

Gentry Sorenson (Region 2): “Rainfall last week ranged from 0.25 inches in Storm Lake to over an inch in other areas.  The D3 drought (extreme drought intensity) has extended in the area that I serve to include parts of Palo Alto County as well as an area that extends further south in Kossuth County. Parts of Clay and Dickinson counties and all of Emmet County that were previously in this status remain in the D3 intensity. Pastures in the area lack height and regrowth from the lack of rainfall. Corn is at the R5 growth stage (dent) with soybeans fields at the R5 to R6 growth stage. In some soybean fields pod abortion can be found on plants that are experiencing heat and drought stress. Corn ears in drought stressed areas are displaying tip back of the corn ear. Incoming calls were concerning drought stress to crops and questions regarding corn and soybean yields.”

Pastures are looking pretty tough in this part of the state. Photo courtesy of Gentry Sorenson.

Northeast Iowa

Terry Basol (Region 4): “Most of the corn in the area is at dent (R5) and up to ¼-milk line progression. Soybeans are primarily somewhere in the R5 stage up to R6. In regards to crop condition, corn and soybeans are doing their best to holding their own amidst the drier weather conditions. For the lighter soil textures in the area, firing in the lower canopy and tip-back on the ears has been observed in corn fields, but for the medium to fine soil textures, most ears are filled out to the end. Soybeans continue to roll or flip their leaves. Recent rains over the past couple of weeks in the territory will still help both corn and soybeans in dry matter accumulation, which results in added test weight.  Hay fields look pretty good considering and should be able to produce another cutting for producers. Disease and insect activity remains relatively low in both corn and soybeans. Rainfall totals over the past weekend ranged from 0.5 inch up to 3 inches in some isolated areas. The map below from the Iowa Mesonet shows that parts of NE Iowa range anywhere from 4 to almost 11 inches deficit of precipitation from average for this year’s growing season (April 1st through August 24th).

Rainfall depature from average across the state of Iowa from April 1 to August 24, 2021. Source: ISU Mesonet.

Josh Michel (Region 5): “Most of NE Iowa has received some much needed rainfall. This came at a critical time as both corn and soybeans are rapidly maturing. Unfortunately, there are some areas in Buchanan and Fayette counties where crops are showing symptoms of severe drought stress. Many corn fields I’ve visited lately have been at R5 (or dent stage) with fields past the ¼ milk line. Some dairy producers have started harvesting corn silage, and I’d expect many others to begin shortly. Soybeans are generally around R6 as the uppermost pods are being filled. While a third crop of alfalfa is getting finished up, I have been seeing and hearing reports of moderate hopper burn persisting in some areas. Pastures continue to hang on in areas where they have received rainfall, otherwise warming temperatures have caused many to go dormant. Recent field calls have centered around corn rootworm management, corn silage, alfalfa and forage seeding management, and cover crop considerations.”

Hopper burn is being observed in some alfalfa fields. A reminder to get out and scout your alfalfa fields. Photo courtesy of Josh Michel.

Central Iowa

Meaghan Anderson (Region7): “Much of my area received rainfall in the last week, but parts of Madison, Warren, and Jasper counties missed out this time. Corn is solidly in the R5 (dent) stage, with many corn fields past the ¼ milk line and some possibly nearing R6 already. Corn has been looking very stressed in the afternoons with the hot weather. Brief yield checks over the last week have shown good kernel counts, but smaller kernels and relatively short ears; we’ll see how much this crop was able to fill in those kernels when the combines start running in just a few short weeks. I’ve seen a little more tar spot in some central Iowa fields, but it hasn’t advanced to the ear leaf in most fields or been very prevalent due to weather. Soybean are solidly in the R6 stage with some of the shorter relative maturity varieties looking like they’re turning in parts of fields. Most calls recently have been about soybean – stem disease, potassium deficiency, sudden death syndrome, and brown stem rot. Now is a great time to check fungicide vs. no fungicide treatments in fields and weed control in order to make notes and plan for future years.”


Good reminder if you see what looks like SDS in fields to split open the stem and double check you are not seeing brown stem rot instead. Photo courtesy of Meaghan Anderson.

East Central, Southeast, and South Central Iowa  

Rebecca Vittetoe (Region 8): “Rainfall has been spotty the past couple of weeks with totals ranging from trace amounts to some areas getting closer to 2 inches. Crops have really been pushed along with the warmer and drier conditions. Most corn fields are at R5 with many at ¼ milk line, and soybeans fields are late R5 to R6. It was not uncommon to see some soybean plants aborting pods the last couple of weeks. Over the last couple of weeks it’s been easier to find tar spot in some EC Iowa corn fields, and I’ve also received questions about sudden death syndrome and/or brown stem rot in soybean fields. Corn rootworms continue to generate a lot of questions. I've also seen and had a few isolated reports of corn aphids."

Virgil Schmitt (Region 9): “Rainfall during the last two weeks in the counties I cover was generally less than 0.25 inch along the I-80 corridor with amounts increasing both north and south of I-80 to over 2.0 inches. In general, temperatures during the last week in the counties I cover were 1 to 2 degrees above normal. Corn is generally in early R5 and soybeans are generally late R5. There are few insect or disease problems at this time. Moisture stress in corn is showing up on coarser textured soils along the I-80 corridor. Calls and farm visits last week mostly involved corn rootworms and weed management.”

Rainfall totals across the state from August 9 to August 23, 2021. Source: https://mrcc.illinois.edu/CLIMATE/Maps/stnMap_btd2.jsp.

Clarabell Knapp (Region 11): “The South Central region has had mostly dry weather the past couple of weeks. A rain system worked its way through the area on August 13th, with precipitation accumulating anywhere from a few tenths to a few inches. Corn fields are in the dent stage (R5), and soybean fields are being seen in full seed (R6) stage. We are starting to see some third cutting of hay occurring. In the past week, the presence of tar spot was confirmed in a few corn fields in Monroe County. Tar spot is a newer disease for the state of Iowa. It was first confirmed in eastern Iowa in 2016. More information on this disease can be found here.”

Tar spot found in a field in Monroe County. Photo courtesy of Clarabell Knapp.

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

Category: Crop ProductionTags: regional updatecrop updatefield agronomistsAuthor: Rebecca Vittetoe

Fall Approaches – Time to Think about Crop Fertility for 2022

Mon, 08/23/2021 - 14:45

As we enter the harvest season, we know we need to be looking forward to the next growing season at the same time. Having plans in place for your 2022 fertilization program before harvest starts is a good idea. Making these plans is tougher this year due to variable yields across the state due to drought stress this season, and the fact that fertilizer prices have risen a lot since this time last year.

Interestingly, some recent calculations comparing the relationship of corn price and fertilizer costs shows nearly the same price ratio now as we saw at this time last year – but the prices of both are significantly higher. Some producers in Iowa will have reduced yields due to drought or other weather problems. Others might be experiencing cash flow restrictions. Still others are just concerned about spending that much money on fertilizer per acre. Those are a few examples of why there might be consideration given to reducing the amount of fertilizer applied to 2022 crops. If that is you, here are a few questions to consider:

1. What was the “cost of doing business” in 2021? In other words, how much phosphate and potash did I apply before this crop and how much did I remove from each field when I harvested my crop? Don’t forget to start by doing that math. Read PM-1688, “A General Guide for Crop and Limestone Recommendations in Iowa,” and use Table 2 to calculate removal from your fields. If yields were reduced, and your normal application rate is based on nutrient removal, you might be able to reduce fertilizer inputs and subsequently the cost of fertilizer inputs.

2. Can I reduce my fertilizer inputs for 2022? It depends. The best way to determine that is to know your soil test levels for P and K. As stated in PM-1688, the percentage of P and K applications expected on average to produce a yield response within each soil test category is 80 percent for Very Low, 65 percent for Low, 25 percent for Optimum, 5 percent for High, and less than 1 percent for Very High. This means that as soil test levels increase, the probability, and the amount, of a positive yield response to fertilization decreases. Additionally, net return decreases and usually becomes negative at High and Very High soil test levels. Consider avoiding applications to fields or field areas that do not need P and K or lime. But do not skip areas with low soil test levels – the odds certainly favor a positive economic response!

3. If soil-test levels are low, do I need to fertilize at a level to rapidly move those soil test numbers up? The ISU recommended rates of fertilizer application in the Low and Very Low soil test categories are greater than crop removal, but do not rapidly build soil test levels. These application levels should produce maximum yield in most conditions, provide profitable crop responses, and will gradually increase soil test levels over time. Applying rates higher than those recommended in PM-1688 will increase soil-test levels faster, but seldom will increase yield further.

4. If it continues to be dry, will my soil-test results be accurate? If possible, try to delay soil sampling until meaningful rainfall because it will result in a better sample and more reliable soil-test results. If you must take soil samples under the current dry conditions, be careful with sampling depth control and that you get the complete soil core in the bag. Note that soil pH test results may be a bit more acidic than it would in normal conditions. Also, soil K test results may be lower than they would be under normal conditions due to less recycling to the soil and less replenishment of soluble or easily exchangeable soil K pools. However, soil P test results probably will be affected little by the recycling issue. See this ICM News article titled “Be Cautious When Interpreting Early Fall Soil-Test Results” for a further discussion.

Category: Soil FertilityTags: soil fertilityphosphoruspotassiumsoil testingAuthors: Joel DeJongAntonio MallarinoCrop(s): CornSoybean

Breaking Plant Breeding Barriers and Crop Production with UAS Technology

Mon, 08/23/2021 - 13:29

Choosing the best crop variety to maximize yield and profitability while still staying within budget is vital to any farm, whether its 100 acres or 100,000. It is also a driving objective for plant breeders that develop these varieties for farmers.

Plant phenotyping is an important part of that decision-making process in plant breeding and for farmers. Agronomy and engineering researchers at Iowa State University and elsewhere have published a paper reviewing the different equipment and methods of phenotyping a field using the latest unmanned aerial system (UAS) technologies while not breaking the bank.

Dr. Asheesh Singh and graduate student Matt Carroll, with his UAS hovering above. Photo by Zach Clemens. 

Iowa State researchers, headed by Matt Carroll, a fourth-year graduate student in Dr. Asheesh Singh’s lab, collaborated with Dr. Wei Guo and colleagues at the University of Tokyo, as well as with researchers at the University of Arizona who provided the cyber infrastructure expertise to make this review possible.

“We are excited about this paper and being Open Access so people can read it and have this information for their use. The approach that Matt and team took was to ensure that we are removing or minimizing the barrier of entry for people who have an interest in utilizing drone-based applications or that can lead to objective or action-based outcomes for farm production or research applications,” Dr. Singh said.

Dr. Singh said the motivation or this paper actually came out of conversations with farmers, who wanted to know how to gather the information on phenotyping themselves. The target for this review paper is not only researchers, but farmers as well and even drone enthusiasts who want the ability to obtain accurate information from crops.

“Matt Carroll is a good example of someone who comes from a farming background who has over the years acquired these sophisticated technical and analytics skills that were not in his routine usage at the farm,” Dr. Singh said.  “And using some of these tools and technologies and then using the data analysis puts him in a prime position as he also understands the constraints of farming as well as the opportunities for growth and profit.”

Carroll explained that a phenotype is the genetic makeup of the plant and the environment it is experiencing. Basically, what you can see, like how green is the canopy, the height—what you can measure.

“You are looking for the best phenotype, and indirectly that means it’s the best genotype, and over time you whittle it down to your best [varieties] in the breeding program,” Carroll said. “When experimental varieties are harvested at the end of the year, there is a lot of documenting, a lot of notetaking looking at yield, disease incidences, and using things like drone based imagery is useful in finding out other information on which lines to keep and which lines to discard at the end of the year.”

The process of using UAS for phenotyping has been around, but is gaining steam. Before it was all legwork, literally.

“Before using this technology, it was going out and taking notes in the field, going plot to plot covering larger areas in field,” Carroll said.

Carroll’s paper reviews the different terminology to introduce UAS, which is a system typically consisting of hardware (i.e., drone and cameras) and the control software (i.e., the programs that help run the hardware efficiently).

“My first project with UAVs was dealing with iron deficiency chlorosis. IDC causes millions in crop loss each year for soybeans, so we were looking at how can we use UAS to identify these deficiencies,” Carroll said. “It is a very visual symptom so that is why we started with that.”

Carroll then spent two weeks at the University of Tokyo with Dr. Guo, learning about UAS and how to extract data from the images.

“Out of that collaboration and internship in Japan we decided to write a review paper on it,” Carroll said. “There is kind of a barrier to entry to phenotyping like this, like what type of cameras do I need, what drone, what else needs to be purchased along with it. We wanted our paper to be something that people could read and give beginners a starting point and allows them to be able to use this technology.” 

UAS are becoming an increasingly useful tool for crop producers all over, Carroll said. He did say that UAS does only see what is on top, so anything below 

Carroll's drone equipped with multispectral cameras. Photo by Zach Clemens.

canopy and or root based traits would need some different technologies, like ground rovers.

“The soynomics team at Iowa State University is looking at above and below canopies to marry these different traits into the optimum outcome,” Carroll said.

He said to make sure to learn all local regulations when flying drones, and make sure to know how to extract the data that is gathered.

“The analysis downstream is important, figuring out how to get your data out of it, they are becoming a lot more accessible, some pay-for services, some open source,” Carroll said. “Still a long way to go but it is becoming a lot better to reducing some of those struggles we have had in the past.”

Weather is also something to keep in mind, as a consistent sky—either consistent cloud cover or no clouds—is an important factor to getting accurate readings.

Some of the cameras Carroll uses take not only regular video, but also multispectral, including infrared and red edge. This captures a lot more information than just regular RGB cameras capture.

“Doing any UAS or phenotype research, we work in transdisciplinary teams where we work with engineers, data scientists and people who aren’t necessarily in the department of agronomy, and that really allows us to do a lot of this research,” Carroll said. “Working together  across disciplines has really allowed us to do a lot of interesting research.”

This research was possible with the financial support of the Iowa Soybean Association, USDA-NIFA and the National Science Foundation.

Category: Crop ProductionTags: UAScrop productionphenotypingplant breedingAuthor: Zachary ClemensCrop(s): SoybeanVideo: 

Corn Silage Harvest and Storage Tips

Fri, 08/20/2021 - 08:10

Historically, corn silage harvest starts within the next two weeks. However, harvest has started early in some droughty areas with light soils. Corn is a high yielding, high energy, low protein forage that is commonly used for growing and finishing beef cattle, in cow-calf production systems, for growing dairy heifers, and for lactating dairy cows. Understanding proper harvest management and timing is critical for producing high-quality corn silage.

Silage that is too wet when harvested may not ferment properly and can lose nutrients through seepage. If silage is too dry, it has lower digestibility because of harder kernels and more lignified stover. In addition, dry silage does not pack as well, increasing the potential for air pockets and mold. Optimum silage moisture at harvest ranges from 50-60% for upright oxygen-limiting silos, 60-65% for upright stave silos, 60-70% for bags, and 65-70% for bunkers.

As a forage crop, corn generally reaches maximum yield and quality around 50% kernel milkline development or R5.5. But due to variability among hybrids and growing conditions, it is necessary to measure silage moisture using a commercial forage moisture tester or microwave oven rather than simply estimating it from the kernel milkline.  Instead, kernel milkline should be used as an indicator of when to collect the first silage samples for moisture testing. A general guideline is to begin moisture testing when the milkline is 1/4 of the way down the kernel for horizontal silos or bunkers, and 1/2 of the way down the kernel for vertical silos. A short article from the University of Wisconsin on whole plant moisture variability in the field, desired moisture for various storage structures, and procedures for moisture determination of corn silage can be found here: http://www.midwestforage.org/pdf/592.pdf.pdf. Directions for using a microwave oven are included in the following publication:  https://store.extension.iastate.edu/Product/Livestock-Determining-Moisture-of-Immature-Corn-Silage-Disaster-Recovery-Series.

Generally, a cutting height of 4 to 6 inches is recommended for corn silage, as it maximizes silage yield and quality. However, drought-stressed corn can accumulate nitrates in the lower part of the stalk, thus increasing the potential for nitrate poisoning, particularly in older livestock on lower-energy rations. The potential for high nitrate silage can be made even worse if drought-stressed silage is harvested within 10 days of a rainfall event, since the rain increases crop uptake of soil nitrogen.  An article on Nitrate Toxicity and Testing from the Iowa Beef Center can be found here: https://www.iowabeefcenter.org/information/IBC50.pdf. For assistance on how to sample a corn field for nitrate levels, the Iowa Beef Center also has this article: https://www.iowabeefcenter.org/information/NitrateSamplingInCorn.pdf.

Silage with high nitrate levels can be managed by dilution with other feeds or by increasing the cutting height up to 12 inches. Cutting at 12 inches leaves the wettest, poorest quality part of the plant in the field. This leads to a decrease in forage moisture by 3-4% and an increase in forage quality by 8-12%. However, it also means a reduction in forage yield by 10-15%. Corn stalks though, are a good source of fiber and the lower tonnage with chopping silage at a higher cutting height typically makes it difficult to justify doing so in the absence of high nitrate levels.

Length of cut and crop processing are also important for obtaining high-quality corn silage. This is because the breakage of cobs and kernels increases surface area, which improves digestibility, reduces cob sorting by cows, and results in higher density silage that packs better. If two or more half or full kernels are present in a 32-ounce cup of silage, then more kernel breakage is needed.

When harvest begins, fill silos rapidly to reduce exposure of silage to oxygen and to reduce fungal growth. For bunker silos, pack silage as tightly as possible in progressive wedges in depths of 6 inches or less. Any extra time spent to thoroughly cover bunker silos and obtain a good seal around bunker sidewalls is also a good investment. Additional information about silages and other wet forages from the Iowa Beef Center can also be found here: https://www.iowabeefcenter.org/feedstuffs.html. In summary, producing and storing high-quality silage can be achieved with proper considerations for harvest management and timing.

Category: Crop ProductionTags: corn silageforage for livestockAuthors: Angie Rieck-HinzJoshua MichelCrop(s): CornBiomass and Forage

New counties confirmed for soybean gall midge in Iowa

Thu, 08/19/2021 - 07:56

My lab has been driving all over western Iowa looking for soybean gall midge. They stop by 3-6 fields in each county and scout for larvae along field edges. This is part of a larger effort funded by the North Central Soybean Research Program to better understand the current distribution of this new pest.

So far, we’ve sampled 30 counties this summer and found soybean gall midge in every county. Most fields are at low infestation levels and would be difficult to confirm without splitting stems open. Some fields do not have larvae. As of today, we have confirmed infestations in three new counties: Emmet, Adams, and Taylor. My crew will continue to scout more central counties this month.

Map created by Ashley Dean, ISU (18 August 2021).

Like in previous growing seasons, infested plants are first detected along field edges. Look for wilted plants and take a closer look at the base of the stem. Spilt the stem to look for larvae feeding inside.

I’ll post more real-time updates about soybean gall midge here and on Twitter (@erinwhodgson). Visit the Soybean Gall Midge Alert Network for distribution maps in Nebraska, Minnesota, and South Dakota. Sign up for the Alert Network by sending an email to Justin McMechan at UNL (justin.mcmechan@unl.edu)

Category: Crop ProductionInsects and MitesTags: midgepestscoutingSoybeanAuthor: Erin HodgsonCrop(s): Soybean

Is that really SDS in a dry year?

Tue, 08/17/2021 - 12:40

I have seen yellow patches in Iowa soybean fields this past week. Plants within these patches have foliar symptoms that appear to be caused by sudden death syndrome (Figure 1; SDS). When talking to the farmers, they are a bit surprised to see these symptoms as seeds in these fields were treated with an “SDS seed treatment” and dry conditions have been present throughout much of the state in 2021.

A few thoughts/observations…

  • I have observed the most SDS on soybeans with new herbicide traits. From past observations, when new traits come to market, they often are introduced in soybean cultivars focused more on yield/standability (not disease resistance).
  • Are the SDS seed treatments working? We obviously want to see reductions in SDS, but most of the fields I have been in do not have check strips, so there is no way to know how much disease would have been there without the seed treatment. In past years, we sometimes still see significant differences in yield between treated and non-treated seed even if there were no obvious differences in foliar symptoms. This may be due to delaying foliar symptom development or reducing the root rot phase of the disease. We have some of these same seed treatments in our small-plot trials, so I am curious to see if this same trend will play out at harvest this year.
  • Some of the yellow patches that hardly look like SDS are indeed still SDS. The lack of rain here in parts of Iowa has resulted in some very non-traditional disease symptoms. I think this is the impact of the root rot phase. Roots are rotted in these patches with stunted and yellow plants, but the yellowing is not from the toxin, but perhaps from the root rot phase of SDS.
  • If you have SDS this year, take note of it because it has not been an ideal year for SDS. However, split stems because I am also seeing some possible brown stem rot in fields (Figure 2; we are doing isolations this week to confirm). Before you make conclusions about how well your cultivar and seed treatments are holding up, be sure you have the correct disease!

Figure 1. Yellowing and death of leaf tissue symptomatic of sudden death syndrome in soybean.

Figure 2. Split soybean stems to help tell the difference between SDS and diseases that have similar foliar symptoms such as brown stem rot.


Category: Plant DiseasesTags: sudden death syndromesoybean diseaseseed treatmentdisease resistanceAuthor: Daren MuellerCrop(s): Soybean

Regional Update: August 2 to August 10, 2021

Tue, 08/10/2021 - 12:25

With parts of northern Iowa now being in a D3 or extreme drought and other areas on the drought monitor expanding, the drier conditions are a concern with what impact they are having on the crops as well as forage availability. Other concerns coming from the field this past week included spider mites as well as corn rootworms. Read on for more specifics about what’s happening in fields across the state.

Northwest Iowa

Gentry Sorenson (Region 2): “Rainfall last week ranged from 0.2 inch in western Emmet County to over an inch per the Iowa Mesonet in the area.  Emmet, northern Clay, the eastern edge of Dickinson and the northwestern part of Kossuth counties have been moved from the severe drought to the extreme drought intensity. In those areas I have seen tip back on corn ears in many cornfields with aborted kernels on the tips.  In soybeans, we have seen stress observed with visual signs of flipped leaves giving the field a silver green colored appearance along with reduced vegetative growth.  Soybean growth stage is at R4 with some soybeans more advanced.  Spider mites have been observed in some growers’ fields, so continue to scout your fields for spider mites along with other pests.  Incoming questions were concerning lack of rainfall, spider mites, and off-target herbicide injury to soybeans.”

Soybean fields and cornfields are showing more signs of drought stress this past week. Photo courtesy of Gentry Sorenson.

Corn ears starting to tip back due to the dry conditions. Photo courtesy of Gentry Sorenson.

North Central Iowa

Angie Rieck-Hinz (Region 3): “Corn is R3 to R4. Soybeans are R5.  With the introduction of a D3 (Extreme) Drought in all of Franklin County, and parts of Cerro Gordo, Wright and Hardin counties, concerns are deepening about forage and pasture supplies, corn nitrate issues with silage, and continued crop stress in corn and soybeans. Rainfall received over the weekend of August 7 and August 8 was highly variable, but Hampton received 2.1 inches of much needed rain. This will likely not impact drought conditions very much as we face a very hot and humid second week of August. There is a lot of mowing and baling of road ditches, grass waterways and CRP. Notable phone calls and conversations this past week included many discussions about “edge effect” and the continued presence of high numbers of corn rootworm beetles.” 

Northeast Iowa

Terry Basol (Region 4): “ Corn ranges from milk (R3) to beginning dough (R4) and the soybeans range from full pod (R4) to beginning seed (R5). The Northern counties of the territory are looking really good, as they have been able to catch some extra rain events, but as you move south in the territory, soil moisture conditions are a lot drier. For the southern half of the territory, crops are showing moisture stress, particularly in the lighter soil textures of the field. Corn is starting to fire on the bottom canopy with leaf rolling in the hot temperatures. Soybeans are turning their leaves so that the bottom of the leaf is turned upwards to help reduce water loss in the plant. As far as pest activity, continue to scout drought affected soybean fields for two-spotted spider mites as well as defoliators such as Japanese beetle, grasshoppers, and bean leaf beetles. Disease presence in corn and soybean fields have been very low due to the warm dry weather conditions. We were blessed with some precipitation this past week that helped the whole territory. For the NE Iowa Research and Demonstration Farm, the Iowa Mesonet reports 5.94 inches this past week, in which 5.85 inches resulted from Sunday, August 8. Within the territory, accumulations ranged from 0.5 up to 8 inches in isolated areas of Floyd and Chickasaw counties.”

Josh Michel (Region 5): “Most of NE Iowa was fortunate to receive some timely rainfall as area crops are quickly maturing. Areas in the northern part of the region and along the Mississippi River received heavier amounts of up to 1.5 inches, while areas along and south of Highway 20 from Manchester to Independence received around 0.25 to 0.50 inch of precipitation. Corn is generally around R3 to R4, while soybeans are generally around R4 to R5. Alfalfa and pasture growth has benefited from the recent rains, and the third cutting harvest of alfalfa is well under way in most areas. Oat harvest is pretty well finished up, with many reports of average to slightly above average yields and test weights. Recent field calls have centered around corn rootworm management, alfalfa and new forage seedings management, disease pressure and fungicide applications.”

Central Iowa  

Meaghan Anderson (Region7): “Much of central Iowa received more than 0.5” of rainfall in the last week, another welcome drink the crop needed very much. Corn is in the blister to dough (R3 to R4) stage and some earlier maturing varieties are at ¼ milk line. Corn in the northern part of my area has been showing some significant stress from the drought, but most fields are holding on well. Soybeans are mostly in the R4 to R5 (beginning pod) stage and some areas seem to be yellowing already. Volunteer corn plants in soybean continue to be very attractive to corn rootworm beetles and will be a likely location for egg-laying yet this year. Calls continue to trickle in about two-spotted spider mites and corn rootworm. More phone calls have come in recently about seeding pastures and cover crops as we look toward fall, crop harvest, and cooler weather.”

Volunteer corn plant found in a soybean field that is attracting corn rootworm beetles. Photo courtesy of Meaghan Anderson.  

East Central, Southeast, and South Central Iowa  

Rebecca Vittetoe (Region 8): “Last week was a fairly dry week across EC Iowa, but some areas did receive some much-needed rain over the weekend. Rainfall totals ranged from 0.1 to 1 or more inches. The heavier rainfall totals were more from parts of Benton, Linn, and Jones counties. The drier conditions are becoming more apparent in parts of EC Iowa, especially parts of Benton, Linn, and Jones, and Poweshiek counties. Some cornfields have started to fire, and you can see the stress in soybean fields with the plants flipping their leaves over and giving the fields that silverish appearance.  I have received a few questions about yellowing in soybeans mainly on thinner soils that is not due to SDS, SCN, spider mites, or early senesce. The fields I’ve looked at, it looks more like a nitrogen deficiency to me. I have also received a few more reports on southern rust and tar spot in corn and seeing a little SDS in some soybean fields. Corn rootworms continue to be generating a lot of questions and discussion as well. Corn is mainly in the R3 (milk) to  R4 (dough) stage, and soybeans are mainly R4 (full pod) to R5 (beginning seed). Other calls or questions focused on late-summer forage seedings, cover crops, and pesticide drift from aerial applications.”  

Virgil Schmitt (Region 9): “Rainfall during the last week in the counties I cover was generally less than 0.5 inch. In general, temperatures during the last week in the counties I cover were normal to 2 degrees below normal. Corn is generally R3, and soybeans are generally R5. There are few insect or disease problems at this time. Fungicides are being applied in some fields even though there is little evidence of disease pressure. Two public areas, one in central Clinton County and one in northern Henry County, received significant drift from aerial fungicide applications. Calls and farm visits last week mostly involved corn rootworms, pesticide drift, weed management, insect management, cover crops, and late-summer forage seedings.”

Rainfall totals across the state from August 2 to August 8. Source: https://mrcc.illinois.edu/CLIMATE/Maps/stnMap_btd2.jsp.

Clarabell Knapp (Region 11): “The past week has been more of a quiet one as field applications wind down along with second cutting of hay beginning to wrap-up. On Thursday, much of the area received a few tenths of rain. Cornfields are typically around the R4 stage while soybeans are in the R4 to R5 growth stage. There has been little insect and disease pressure, but I have seen some gray leaf spot and southern rust in corn.”

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

Category: Crop ProductionTags: regional updatedroughtspider mitescorn rootwormAuthor: Rebecca Vittetoe

New Aerial Applicator Study Manual and Exam

Mon, 08/09/2021 - 08:25

A new Aerial Application Manual (CS 26) is now available for individuals planning to take the aerial applicator exam to become certified or renew their certification. This manual will assist aerial applicators and aerial applicator consultants in preparing to take the commercial pesticide applicator Category 11, Aerial Application exam, administered by the Iowa Department of Agriculture and Land Stewardship. The new manuals are available at the Iowa State University online store.

Starting September 1, 2021, aerial applicator exams will be based on information covered in the new manual as well as material from the Core Manual, Category 1A, Agricultural Weed Management, Category 1B, Agricultural Insect Management, and Category 1C, Agricultural Crop Disease Management. The Category 11, Aerial Applicator exam can be taken online or in-person. Pesticide applicator testing information, including a tutorial video, is available on the Iowa Department of Agriculture and Land Stewardship Pesticide Bureau website.

Category: Pesticide EducationTags: Pesticide applicator manualAuthor: Elizabeth Danielson