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Corn dry down calculator goes live

Mon, 09/09/2019 - 21:39

One of the pressing questions this fall is when corn will reach maturity and if there is going to be enough time to dry down in the field. We have developed and released a corn grain dry down calculator that can help determine how quickly corn grain moisture will dry down in the field. The calculator can be applied at any location across the Corn Belt, from North Dakota to Missouri and from Nebraska to Ohio. Users select a map location and then enter a date and a kernel moisture content at that date. In turn, the tool projects in-field corn dry down. This tool can be used to estimate when a specific field will reach appropriately moisture for mechanical harvest (15-20% moisture) based on user input. The tool allows scenario planning by entering estimated dates and grain moisture for crops that are yet to mature compared to fields where crops have already matured. This is facilitated by the users ability to enter known (or estimated) dates and grain moisture.

Below is an example on how to use and interpret the tool. Let’s take a field in Story County, Iowa that reached black layer on 15 September at 30% grain moisture. In this situation it is estimated that on 19 September grain moisture will be 24.8% and 24 September grain moisture will be 21.8%. Furthermore, the grain dry down rate is estimated to slow down after 1 October. The yellow shaded area is the variance in grain moisture based on historical weather.


This tool prediction uses the daily temperature and relative humidity as the input for an algorithm developed from a multi-year, multi-location research trial in Iowa. This algorithm development can be found at: Evaluating maize and soybean grain dry down in the field with predictive algorithms and genotype-by-environment analysis. Where possible current temperature and relative humidity data is used. Forecasting beyond the current date is based on historical temperature and humidity information.

The effect of precipitation on dry down is indirectly captured by relative humidity whereby on rainy days the drying power of the air is low which is reflected by high relative humidity. We tested the prediction using data spanning from eastern North Dakota to southern Iowa and the tool predicted moisture decline with an error of 1.8%. The tool is best suited and recommended for use when crops reach physiological maturity, however, predictions can be made before that point.

Category: Crop ProductionGrain Handling and StorageTags: corn managementgrain dry downgrain moisturemoisture equilibriumAuthors: Mark LichtSotirios ArchontoulisCrop(s): Corn

Late season pest activity

Fri, 09/06/2019 - 08:21

This week was my last field day of the summer – it’s always is a signal the season is ending. I noted plants are senescing fairly quickly on my drive to Kanawha. However, there are still a few insects active on field crops, and worth scouting for this weekend.

Corn aphids are problematic in some cornfields this week. Their honeydew is promoting a black sooty mold that can interfere with photosynthesis. The sugar excrement can also cause issues with combines at harvest. Photo by Brian Lang, ISU.

In addition to grasshoppers, bean leaf beetles can cause direct injury to soybean pods and seeds this month. Photo by Brian Lang, ISU.

Category: Crop ProductionInsects and MitesTags: insectSoybeanCornpestscoutingAuthor: Erin HodgsonCrop(s): CornSoybean

Ergot: Be aware when harvesting small grains and grasses

Wed, 09/04/2019 - 10:35

One plant disease to keep a lookout for when harvesting grains and grasses for animal and human consumption is ergot. The ergot pathogen generates toxic alkaloids that potentially could create problems with livestock feeding, and when trying to market a small grain crop. The Crop Protection Network recently published an article outlining six things to be aware/mindful of when harvesting your small grains, including:

  • Diagnosis
  • Favorable conditions
  • Potential dangers
  • Inflected grain uses
  • Ergot in pastures
  • Ergot in grain

To view the full article, follow this link.

Category: Crop ProductionGrain Handling and StoragePlant DiseasesTags: ErgotSmall Grainsgrassesforage managementAuthor: Ethan StoetzerCrop(s): CornMinor crops

Sampling for the End-of-Season Corn Stalk Nitrate Test

Wed, 09/04/2019 - 08:35

Sampling corn stalks this fall will likely be later than normal due to the delayed planting in many Iowa cornfields. The overall suggestion is to wait until crop maturity, and sample within 1-3 weeks after kernel black layer. This does not work well for silage corn, so the suggestion is to collect stalk samples at the time of silage harvest or within 24 hours after harvest (as long as no rain between harvest and sampling). The publication describing the End-of-Season Corn Stalk Nitrate Test was updated in 2018 (Use of the End-of-Season Corn Stalk Nitrate Test in Iowa Corn Production, CROP 3154). That publication describes the sampling protocol and interpretation of results. The old interpretation categories were adjusted; now three categories of Low (< 250 ppm), Sufficient (250-2,000 ppm), and High (> 2,000 ppm). As noted before, the most reliable interpretation is with High concentrations (> 2,000 ppm) indicating more than enough plant-available nitrogen for that year. Also, as noted before, don’t base nitrogen management changes on only one-year results; instead sample multiple years to build a trend database. The stalk segment to sample remains the same, an 8-inch segment from 6 to 14 inches above the ground. Avoid sampling odd plants or plants damaged by disease or insects. Collect 15 stalk segments per sample area. Place stalk samples in paper (not plastic) bags. If needed, refrigerate until taking or shipping samples to the lab.

Category: Soil FertilityTags: nitrogen managementCorn Nitrogen Fertilizationtissue samplingAuthors: John SawyerAntonio MallarinoCrop(s): Corn

2019 Western Iowa Palmer Amaranth Tour

Wed, 09/04/2019 - 07:55

Sensing an impending lackluster performance by the Cyclone football team, I spent the Saturday of Labor Day weekend touring several Palmer amaranth infestations in western Iowa. This is the 6th year of this trek, the first stop is always Harrison County at the first reported Iowa infestation of Palmer amaranth. The primary field (approximately 25 acres) was dominated by Palmer amaranth in 2013 when Palmer was first identified.  Since then the population has continually declined. This year the field was in prevented planting and was recently tilled to control weeds.  I was unable to find any Palmer among the waterhemp and marestail carcasses in the field.  An area across the road established in native perennials has had scattered Palmer amaranth plants over the years.  This year it had been converted to alfalfa and a few small patches of Palmer amaranth were present.  I didn’t find any Palmer plants along the road leading to the field which had been present in previous years.  

No Palmer amaranth was found among the carcasses of waterhemp and marestail in prevented planting field in Harrison County.


A new stop on my annual tour was a 15-acre field in a commercial area of Council Bluffs that I learned was infested with Palmer last year.  This field was also in prevented planting, but unlike the Harrison County field had a healthy infestation of Palmer amaranth.  The field appeared to have been tilled earlier in the summer, but either there was a late flush of Palmer or early-establishing plants survived the tillage.  Plants were setting seed, so even if actions were taken in the near future the seed bank would be replenished.

Less effective management of Palmer amaranth in prevented planting field in Council Bluffs.

I was on my way to Fremont County when my daughter called to say she could get off work for lunch, so I turned around at the first exit on I-29 south of Council Bluffs.  While getting back onto I-29 I spotted Palmer amaranth on the side of the entrance ramp.  This was ‘exciting’ since it was the first time I have found Palmer amaranth in Iowa without having been notified of its presence.  After lunch as I headed to Fremont County I got off the exit again to further investigate the infestation.  I was surprised to find the Palmer amaranth extending for over a half-mile along the road.  The Palmer was restricted to the area immediately adjacent to the road and didn’t extend into the area of ditch with a healthy stand of smooth brome.  

Although the source of this infestation is unknown, there is a large grain processing facility nearby that is a logical source for Palmer amaranth seed.  I was surprised at the size of the infestation since annual weeds typically don’t do very well on our roadsides. I thought maybe the roadside recently was regraded which would create a more favorable environment, but the county engineer reported the last construction at this site was in 2009.  The county engineer had been unaware of the infestation, but said the county would take immediate action. The adjacent soybean field had a lot of waterhemp, but I didn’t spot any Palmer amaranth in the field.  

Palmer amaranth on roadside in Mills County.

The Palmer amaranth in Fremont County is inside the boundaries of a town decimated by this year's flood.  There was much less Palmer  than in previous years.  It will be interesting to see if the Palmer amaranth seed was moved to new areas by floodwaters and results in a spread of the weed.

The final stop was in Page County on the grounds of a commercial ag operation that has been home of a small infestation since 2013.  As in previous years there were a few scattered plants present on the property. It is nice that the infestation isn’t getting worse, but discouraging since it wouldn’t take much effort to remove these plants and stop them from replenishing the seed bank. There was no Palmer in the adjacent soybean field.

Summary:  While I don’t gather systematic measurements of the populations at these sites, the tour allows me to see whether Palmer amaranth is increasing or decreasing in time.  It is encouraging that Palmer amaranth isn’t becoming a dominant component of the weed community and isn't expanding into adjacent areas.  The Harrison County site was by far the worst infestation of the three when they were discovered in 2013, and in the past two years I haven’t found any plants in the field where Palmer was first identified.  There have been limited numbers of plants outside of the field that could be eliminated without much effort (same as at the Page County site), but the overall progress in eradicating Palmer amaranth is encouraging.

The most disappointing finds were the poor management in Council Bluffs and the discovery of Palmer amaranth along the road in Mills County.  If we are going to stop or limit the movement of Palmer amaranth in Iowa, everyone involved in crop production needs to be observant for new infestations and prevent them from becoming permanently established. The ability to drive down the infestation in Harrison County demonstrates this weed can be beat.  The lack of a large, established Palmer amaranth seed bank in nearly all of Iowa’s crop fields makes this a winnable fight.

Previous tour blogs:

Category: WeedsTags: palmer amaranthAuthor: Bob Hartzler

Northern Iowa Research Farm fall field day September 5 at Kanawha.

Thu, 08/29/2019 - 15:12

Thistle caterpillars, late season crops disease and crop development will highlight the September 5 fall field day at the ISU Northern Research and demonstration farm fall field day.

Registration and refreshments will begin at 9 a.m. A noon lunch will be available. The field day is open to the public and includes complimentary refreshments and lunch. 

The farm is located at 1040 James Ave., Kanawha – about two miles south of Kanawha on County Road R35. 

The program begins at 9:30 a.m. with Matt Schnabel, Northern Research Farm superintendent, giving a review of the growing season and a discussion of summer activities. 

Alison Robertson, professor and extension specialist in plant pathology and microbiology at Iowa State, will talk about late season corn diseases – including some discussion on tar spot of corn.

Paul Kassel will discuss the impact of the late planting and summer growing conditions on crop development. 

Angie Rieck-Hinz, ISU Extension and Outreach field agronomist, and Karen Wilke, coordinator with The Nature Conservancy, will discuss cover crop management for 2020 and some local funding options. 

There are Certified Crops Advisor credits available. There is one credit each in Soil Water, Pest Management and Professional development. 

Category: Crop ProductionTags: Corncover cropsSoybeanAuthor: Paul KasselCrop(s): Corn

Have you seen this bug?

Thu, 08/29/2019 - 07:33

Yesterday, while waiting for my field day stop to begin at the ISU Northeast Research Farm, I noticed a bright green insect land on my leg. At first glance, I thought it was the threecornered alfalfa hopper (Photos 1 and 2). I’ve never seen one in real life and was surprised to see it in northeastern Iowa (and what good luck to land on me!). It is a frequent soybean and alfalfa pest in the south but my lab has never collected it during all my sampling in soybean since 2009. Back in the office today, I tried to confirm the species of this beautiful bug. After a little searching online (thanks, BugGuide!) and getting a closer look with a microscope, I think it is buffalo treehopper (Photo 3).

Photo 1. Threecornered alfalfa treehopper. Clemson University, www.ipmimages.org.

Photo 2. Male threecornered alfalfa treehoppers have a red-orange stripe on the smooth “shoulders.” Graham Montgomery, www.bugguide.net.

Photo 3. Buffalo treehopper, note triangular “thorns” behind the head. Erin Hodgson, ISU.

Threecornered alfalfa hopper nymphs and adults use their piercing-sucking stylets to feed. Repeated piercing in the same area of the main stem generates a swollen area and can result in a girdled effect, causing the stem to lodge and break off. The buffalo treehoppers are not considered field crop pests, and feed on black locust, elm, goldenrod and willow.

Category: Crop ProductionInsects and MitesTags: insectsamplingSoybeanAuthor: Erin Hodgson

End of August Crop Update for Northwest Iowa

Wed, 08/28/2019 - 15:06

Check out what ISU Extension and Outreach field agronomists in NW Iowa are seeing and hearing in their areas regarding crop progress and issues showing up in crop fields.

Joel DeJong (Cherokee, Ida, Lyon, Monona, O'Brien, Osceola, Plymouth, Sioux, and Woodbury Counties ): “In the NW corner of Iowa, most of the counties received a nice rain in the last two weeks. Lighter soils still show some stress, but most acres look good from the road at least. In the field, the crops look pretty good, too, except many aren’t nearly as mature as I would like of see for the last week of August. The June planted corn I observed late last week was still in the milk stage. There is a lot of concern about not only an early frost, but even some concern about a normal frost for corn along the Minnesota border with the present cooler than normal forecast. In most years, silage chopping has started by now. I have seen no activity so far this year. I have seen some disease pressure, but it doesn’t appear to be widespread in the region. Soybeans are starting to fill pods, and the southern part of the area has reported scattered patches of white mold this past week. Soybean aphids have reached treatment thresholds in scattered locations, too. Overall, this corner of the state looks quite good, except for the stage of growth for the last week of August.”

Paul Kassel (Buena Vista, Clay, Dickinson, Emmet, Hancock, Kossuth, Palo Alto, Pocahontas, Sac, and Winnebago Counties): “Soybean aphids have been the question of the week. Aphid numbers have continued to increase during August. Farmers are encouraged to make random checks throughout the field for soybean aphids and use the 250 aphid/plant threshold on 80% of the plants. Usually treatment is not beneficial after the R6 stage (soybean fills the pod cavity at one of the top four nodes) of development. A third generation of thistle caterpillars can be find in some soybean fields as well. The early May planted corn is in the hard dent stage and could be expected to reach the black layer stage of development in about three weeks.  June planted corn is in the late milk/early dough stage and could be mature in about five weeks.”   

A third generation thistle caterpillar found in a Buena Vista County soybean field. Photo courtesy of Paul Kassel.

Find your local ISU Extension and Outreach field agronomist here!

Category: Crop ProductionTags: crop updatefield agronomistsAuthors: Joel DeJongPaul Kassel

End of August Crop Update for East-Central, Souteast, and South-Central Iowa

Wed, 08/28/2019 - 10:06

Check out what ISU Extension and Outreach field agronomists in EC, SE, and SC Iowa are seeing and hearing in their areas regarding crop progress and issues showing up in crop fields.

Rebecca Vittetoe (Benton, Iowa, Johnson, Jones, Keokuk, Linn, Mahaska, Marion, Poweshiek, and Washington Counties): “Over the last two weeks, we’ve caught some much-needed rain in this part of the state with rainfall totals ranging anywhere from about 1 inch up to 5 inches or more in some areas. From a crop maturity perspective, corn ranges from R3 to R5 and soybeans are mostly R5. Tar spot has been found in several corn fields in Iowa again this year. At this point there is not much we can do other than making note of where it is at. If you suspect that you have Tar Spot, please reach out or send a sample in to the Plant and Insect Diagnostic Clinic. We are collecting samples for research. I’ve noticed and have gotten quite a few calls regarding yellowing in soybean fields. A lot of what I have seen looks like potassium deficiency, but I have seen a few fields that the yellowing looks more like top dieback.”

Virgil Schmitt (Cedar, Clinton, Des Moines, Henry, Jackson, Lee, Louisa, Muscatine, and Scott Counties): “Rainfall the last two weeks ranged anywhere from 1 to 5 inches in my area. Corn ranges from R3 (June planted corn) to R5 (April planted corn). The R5 corn is about 0.5 milk line. Soybeans are mostly R5. Group 4 injury calls are continuing. Potassium deficiency and/or top die back is showing up in a few fields. Pastures are starting to recover. Inquiries about and Group 4 and group 15 herbicide injury on soybeans dominated calls last week. Weed escapes and late-summer forage seeding were also common calls.”

Monday August 26, 2019 analysis for the last 14 days. Source: https://water.weather.gov/precip/

Josh Michel (Appanoose, Davis, Lucas, Jefferson, Monroe, Van Buren, Wapello, and Wayne Counties): “Widespread rain showers brought over an inch of rain to much of SC/SE Iowa last week, with heavier amounts up to three and half inches in some areas. Pastures and hayfields are greatly benefiting from the precipitation and cooler temperatures. April planted corn is generally around R5 and looking good. The later June planted June corn is around R2 to R3. Early planted soybeans are mostly around R5 to R6, while late planted soybeans are generally around R2 to R3. Common field calls and questions have included foliar diseases in corn (common rust, gray leaf spot and northern leaf blight), fall stalk nitrate testing, third generation thistle caterpillars, late season weed escapes, and herbicide injury in soybeans.”

Find your local ISU Extension and Outreach field agronomist here!

Category: Crop ProductionTags: crop updatefield agronomistsAuthors: Virgil SchmittJoshua MichelRebecca Vittetoe

Join us for the fall field day at the Southeast Research and Demonstration Farm on September 5, 2019

Wed, 08/28/2019 - 09:27

Mark your calendar for the September 5th Fall Field Day at the Southeast Research and Demonstration Farm near Crawfordsville! The event will begin at 5:30 p.m. with a complimentary meal and registration. The tour starts at 6 p.m. and will feature the following topics:

  • Season Review by Cody Schneider and Myron Rees, Southeast Research Farm Superintendents
  • Water Quality: Edge-of-Field Practices by Matt Helmers, ISU professor and extension agricultural engineer
  • Market Facilitation Program and Crop Market Outlook by Ryan Drollette and Charles Brown, ISU Extension and Outreach farm management specialists
  • Current Crop Conditions and Harvest Challenges by ISU Extension and Outreach field agronomists Virgil Schmitt, Josh Michel, and Rebecca Vittetoe, and extension ag engineer Kristina Tebockhorst

Attendees can discuss concerns and ask questions with each of the speakers. Certified Crop Adviser continuing education credits will be available (0.5 S.W.M., and 1.0 C.M.).

This field day is free and open to the public with no pre-registration required. The meal is sponsored by the research farm association; Louisa, Washington, Henry, Jefferson and Des Moines County Farm Bureaus; and Hills Bank and Trust Co. 

To reach the farm, follow U.S. Highway 218 one and three quarters miles south of Crawfordsville, then two miles east on county road G-62, then three-quarters of a mile north.  Signs will be posted.

Category: Crop ProductionTags: fall field dayAuthors: Virgil SchmittJoshua MichelRebecca Vittetoe

Update on Crop and Soil Status Across the I-States – August 21, 2019

Thu, 08/22/2019 - 15:02

Update on crop and soil status across the I-states – August 21, 2019

This year the FACTS project is providing a suite of regional scale maps to assist decision making. The data provided is based on APSIM model simulations which are driven by current and forecasted weather data, soil data, NASS planting date data and different corn hybrids and soybean varieties across the landscape. The maps were created from 30 field simulations per county. In this article we provide an update on weather, soil, and crop variables.

Precipitation: The May 1 to present precipitation accumulation is 2–6 inches above normal for most of the three I-states. This is largely the result of high rainfall amounts in May and limited rainfall in July. According to Weather Prediction Center, during next week (August 20 to 27) rain is expected across the area with higher precipitation to occur in southern Iowa.

Temperature: Growing degree day (GDD) accumulation from May 1 to present is about 50 to 150 GDD below normal in Iowa and about 50 to 150 GDD above normal in Illinois and Indiana. Since May 1, northern Iowa has accumulated 1800 GDD while southern Illinois more than 2500 GDD. For the next week, GDD accumulation is projected to be 20 GDD below normal for Iowa and 20 GDD above normal for Illinois and Indiana. Iowa’s 50% corn planting progress was about 2-3 weeks earlier than Illinois and Indiana. On the other hand, Illinois and Indiana are accumulating GDD faster, which suggests that the difference in crop maturity among states will be less than anticipated despite the 3-week difference in planting.

Soil moisture and rooting depth: Current soil moisture levels across the soil profile are within 75 to 115% of field capacity, which is considered ideal for plant growth and soil N mineralization. Crops are taking up water from the soil at a rate of about 0.20 inches/day. At present, model simulations indicate that both corn and soybean have roots at a 50 to 60-inch soil depth across much of the area.

Soil N mineralization and crop N uptake: On average for 60% of the region, soil N mineralization since May 1 is at or above normal. The exception is a transect from east central Iowa to southeast Indiana where soil N mineralization is below normal. However, at this period, soil N mineralization is of less importance for corn as corn plants have taken up most of their N needs and current N uptake is at about 1.5 pounds N/acre/day. In contrast to corn, soybeans are taking up 2-3 times more N than corn.  At the present soybean stage, N-fixation can provide up to 2.7 pounds N/acre/day. The current soil moisture is ideal to support high N fixation rates.    

Crop photosynthesis and grain accumulation: Currently corn photosynthesis, estimated as pounds C/acre/day, is 75 pounds C/acre/day while soybean photosynthesis is about half as much. According to USDA NASS, 29.4 million corn acres and 26.4 million soybean acres have been planted across the three I-states. Thus, the total amount of carbon that is fixed through photosynthesis across the area is about 3.2 billion pounds of C/day! Nearly all that C is being assimilated as in corn kernels and soybean seed. Across the area, model simulations for the next week indicate corn grain yield accumulation of 4.5 bu/acre/day.

In conclusion, the temperature and radiation levels in September, which are currently unknown will determine the date of crop maturity, final yield levels, and expected rate of grain moisture dry down.

Category: Crop ProductionTags: FACTSrooting depthweather impactgrain accumulationAuthors: Sotirios ArchontoulisMark LichtCrop(s): CornSoybean

Allee field day to discuss cover crops

Wed, 08/21/2019 - 17:00

Farmers and agribusiness are invited to the Allee Demonstration Farm for a field day on Tuesday August 27.  Coffee and registration will be at 9:30 with a free lunch at noon.  

The Allee Research Farm is located at 2030 640th St., Newell – 1 mile southwest of Newell and a quarter mile east. 

The focus of the field day will be cover crops. Attendees can see a demonstration of cover crops seeded in June as well as hear about fall seeded cover crops. 

Lyle Rossiter, Allee farm superintendent, will discuss cover crop research at the Allee farm.

Michaela Klump, USDA NRCS in Buena Vista County, will discuss cover crop funding resources for the 2020 growing season. 

Mike Witt, ISU Extension and Outreach field agronomist, will talk about research on cover crop species for interseeding into standing crops. 

Paul Kassel, ISU Extension and Outreach field agronomist, will discuss planting a soybean crop into a fall seeded cover crop. 

Field day visitors are invited to the Jamie Adams farm, at 5961 185th street, Newell, after the noon lunch. Adams will discuss his use of cover crop as a forage crop and his cover crop plans for the 2020 growing season. 

Category: Crop ProductionTags: Corncover crops. soybeanAuthor: Paul KasselCrop(s): Corn

2019 Corn Grain Filling Progress in Iowa

Wed, 08/21/2019 - 09:02

According to the latest NASS report, the 2019 corn crop is about 2-weeks behind normal in terms of reaching dent stage. What are the implications of this delay in grain filling period and end of season yield? We address this question by examining two key weather variables; solar radiation and temperature.

Solar radiation interception is expected to be 15% lower during the dent phase in 2019 compared to past years (Fig. 1). This is because daylength, and therefore amount of solar radiation, decreases as we move from August to September. An unknown factor is the clouds during 2019 dent phase, which may compensate for the decreased radiation energy. Solar radiation is the main driver for crop photosynthesis, which for the present week is estimated at 210 lbs dry matter/acre/day for Iowa (see FACTS website). Crop photosynthesis is strongly related to corn grain accumulation, which for the present week is estimated at 4.5 bushels/acre/day for Iowa (Fig. 2). For reference, the maximum grain accumulation rate can be up to 7 bushels/acre/day.

Fig 1. Average solar radiation (left panel), average daily temperature (middle panel) and minimum temperature (right panel) for central Iowa. Data points are averages over 10-day period (e.g. 5 June is the average from 1 June to 10 June). Horizontal green lines in the middle and right panel indicates the base temperature of 50oF and killing frost temperature of 32oF, respectively. Blue and red horizontal lines indicate the normal grain fill duration (blue line) and the expected 2019 grain fill duration (red line). 

Fig 2. Simulated current grain accumulating rates (in bushels per acre per day) across three I states. Data are from the FACTS project simulations.

Temperature during the dent phase is also expected to be around 5oF lower in 2019 than past years (Fig. 1). A 2-week delay in the start of dent stage will probably delay corn maturity by 3 weeks because temperatures begin decreasing from late August to September. When crops can be expected to reach maturity this year depends on the planting date and hybrid maturity combinations. In general, crops planted before June 1 should not have an issue reaching maturity in Iowa. Historically, the average temperature will be above 50oF until October 10 for central Iowa, while the first frost likely would occur after October 20 in central Iowa, thus crops will likely make it to maturity. The key issue this year will be the dry down period for grain moisture to reach 15-20%. While it is expected that with normal fall conditions, even late planted corn will reach maturity, grain dry down will be slower resulting in wetter corn at harvest

For the state of Iowa, the 2019 corn yields can be expected to be lower than the past 3 years because temperature and radiation during the grain filling period is less than would typically be expected due to later than normal planting dates. However, there is a lot of variability across the state for planting date, corn maturity, and weather conditions that will be addressed in a follow up article.

Category: Crop ProductionTags: radiationtemperaturegrain fillingcorn yieldAuthors: Sotirios ArchontoulisMark LichtCrop(s): Corn

US Drought Monitor Update and How it Works

Fri, 08/16/2019 - 08:22

We've gone from being too wet to the other extreme of being dry in parts of the state. Below is a summary of the most recent US Drought Monitor (USDM) map for the state of Iowa and a brief explanation of what data goes into making the USDM.

Current Conditions in Iowa.

Yesterday (August 15), the latest USDM map was released.  As of Tuesday, August 13, Abnormally Dry (D0) conditions covered 43.1% of Iowa, up from 36.39% the previous week. Additionally, 9.5% of the state is now considered to be in a Moderate Drought (D1).

Below is a table from Drought.gov explaining the various levels of drought.

What determines these levels of drought?

Weekly recommendations to the USDM author are based on a variety of variables and on-the-ground impact reports. Recommendations are formed using a “convergence of evidence” approach in which data such as rainfall deficits, top and sub-soil conditions and various moisture indices are considered and compared to physical impact reports. When a majority of the evidence supports a drought class designation (D0-D4), a recommendation is submitted to the USDM author after data cut off at 7:00 am CDT on Tuesday. The final map is released at 7:00 am CDT the following Thursday. The USDM map is not a forecast but rather a representation of current conditions.The monitor focuses on broad-scale conditions, and local conditions may vary.

Category: Crop ProductionTags: droughtWeatherdry conditionsAuthor: Justin Glisan

Considerations with late summer seeding of forages

Thu, 08/15/2019 - 14:44

Now is the time to be doing late summer seeding of forages. This ICM article Steve Barnhart, retired Extension forage specialist, wrote does a nice job providing basic information to successfully establish a late summer seeding of forage. Read on for suggested times to complete a late summer seeding and for weather/environmental considerations when doing late summer seedings.

With a late summer seeding, seedlings need 6 to 8 weeks of growth after emergence to have adequate vigor to survive the winter. Suggested times to complete a late summer seeding are: 

  • by August 10 in the northern third of Iowa
  • by August 20 for the middle third of Iowa
  • by September 1 for the southern third of Iowa

Planting one to two weeks later than what is stated above often will work; however, later seedings are much more dependent on favorable fall weather.

For a late-summer forage seeding to work, we need good seeding technique and timely rainfall. Unfortunately on the rainfall we are running short in parts of the state. There is a higher risk of seeding failure when planting seeds in drier soil as there may be enough moisture to get the seed to germinate but not enough for seedling establishment.

There looks to be anywhere from a 10 to 30% chance of rain over the weekend and start of next week. The National Weather Service is also predicting a higher probability of above average precipitation in their 8 to 14 outlook (as of August 14). While there is hope for moisture for a late summer seeding, we'll have to play it by ear based on what Mother Nature decides to do.  

Category: Crop ProductionTags: late summer seedingdry conditionsAuthor: Rebecca VittetoeCrop(s): Biomass and Forage

Regional Crop Update: August 5 to August 13, 2019

Tue, 08/13/2019 - 14:12

Limited rain fell across the state this past week, and approximately 36% of the state is considered to be abnormally dry according to the U.S. Drought Monitor as of last Tuesday, August 6. In addition to the dry conditions and moisture stress, other issues ISU Extension and Outreach field agronomists saw this past week included soybean gall midges, soybean aphids, the start of a third generation of thistle caterpillars, growth regulator injury in soybeans, and Tar Spot in corn. Read on to see what’s happening in specific areas across the state.

Northwest Iowa

Joel DeJong (Region 1): “Last week was pretty dry, but most fields are doing OK. Sandy soil areas are showing the stress, but those are the only areas showing significant stress right now. Corn ranges from just finished with pollinating for the late corn to dough stage for the earlier corn. Some gray leaf spot is present and scattered rust, but most fields are not showing a lot of disease currently. Soybeans appear to be mostly late R3 to R4, with the early fields approaching R5. Some frogeye is present, you can find gall midge damage on field borders quite easily in some counties, and soybean aphids are beginning to show up. Aphids might be close to the threshold at the NW Research Farm this week. A good rain would be welcome. Calls regarding off-target movement of dicamba in soybeans continue to come in.”

Paul Kassel (Region 2): “An analysis of two planting dates using the same 99-day corn hybrid planted in Clay County shows that the May 5 planting date should reach black layer development on September 17. The same 99-day hybrid planted on June 5 in Clay county predicts an October 20 black layer date. The actual black layer in this example will likely be a few days before October 20. Corn hybrids require about seven Growing Degree Days (GDD) less to mature for every day of planting delay (about 140 GDD less in this example). There is a 56% chance of a 28oF freeze event before October 20. A few farmers are reporting low numbers of soybean aphids. A few days ago soybean aphids were about nonexistent, so take time to scout your fields. There have been lots of painted lady butterflies flying around. It remains to be seen if we will see a third generation of thistle caterpillars in our fields. Regardless, farmers are encouraged to check their soybean fields for insect damage and defoliation through mid-August.”

The same 99-day corn hybrid planted on June 5 (top) and planted on May 5 (bottom) in Clay County. Photo courtesy of Paul Kassel.

Central Iowa

Meaghan Anderson (Region 7): “Most of Central Iowa went another week with little to no rainfall, but some areas received a well-needed shower to keep grain fill going. Some corn and soybean fields are showing stress from the warm temperatures and rainfall deficit, especially when you get out in (corn) fields and look at things more closely. Most corn is in the R4 stage, with some of the earlier planted fields beginning to dent already. Gray leaf spot is still the most prevalent disease, but I’ve received numerous photos of Physoderma brown spot as well. Insect pressure is low overall, but some fields have had issues with Japanese beetles along field edges. I noticed a pocket of high northern corn rootworm beetle pressure in SW Dallas and NW Madison counties this last week. Soybeans are mostly in the R4 to R5 growth stage and are dominating my phone calls. In the last week, I started noticing thistle caterpillar eggs on the upper side of soybean leaves again; these will take about a week to develop into caterpillars. We also confirmed the presence of soybean gall midge in Dallas County, so please be out scouting for it. I’ve also started to get reports of soybean aphids; however there does appear to be a lot of variability in populations so also be scouting for aphids.”

Soybean gall midge larvae were confirmed in Dallas County this past week. Photo courtesy of Meaghan Anderson.

A thistle caterpillar egg laid on the upper side of a soybean leaf. Photo courtesy of Meaghan Anderson.

East Central, Southeast, and South Central:

Rebecca Vittetoe (Region 8): “Last week was another dry week across most of my area. The crops, hayfields, and pastures are showing signs of stress. Corn ranges from VT to R4 and soybeans are mainly R3 to R4. From a disease perspective, gray leaf spot and common rust tend to be the common diseases found in corn, and soybeans continue to have little to no disease pressure. Tar spot has been found in a couple of my more northern counties again this year. There have been plenty of painted lady butterflies flying around the area. I suspect that this week we could start to see the third-generation larvae in soybean fields. I continue to get calls regarding growth regulator injury in soybeans. Other calls and field visits have been on pasture management, fall seeding of forages, and late-season weed escapes.”    

Departure of normal precipitation across the state from July 1 through August 12. Source: Iowa Environmental Mesonet.

Virgil Schmitt (Region 9): “Rainfall last week was mostly between 0.5 and 1.0 inch, with western Lee receiving less than 0.5 inch, a little streak through Cedar, Muscatine, and Scott Counties receiving between 2.0 and 3.0 inches, and most of Jackson County receiving between 1.0 and 2.0 inches. Corn ranges from R2 (June planted corn) to R4 (April planted corn). Some of the R4 corn is starting to show some early signs of denting. There is a little rust and gray leaf spot. I’m receiving reports of more tar spot in Jackson County. Soybeans are from R4 to R5. There is little disease pressure at this point. Group 4 herbicide injury calls are continuing. Oats are mostly harvested. Pastures are turning brown. Potato leafhoppers continue to be an issue in hay. Inquiries about and Group 4 herbicide injury on soybeans and fungicides on corn and soybean dominated calls last week. Other calls included potato leafhoppers, weed escapes (mostly waterhemp), drift, and anthracnose leaf blight on corn.”

Rainfall totals across the state for the past seven days as of August 12. Source: https://water.weather.gov/precip/.

Josh Michel (Region 11): “While some areas in the eastern part of my region did receive up to a half inch of rain, many areas in south central Iowa remained dry over the last week. Fields and pastures have been showing signs of stress with the lack of moisture. Reports of grasshoppers and potato leafhoppers continue in hayfields. April planted corn is mostly around R3 to R4 with the late planted June corn being at VT to R1. Early planted soybeans are mostly around R4, with a few fields possibly reaching R5 later this week. Common questions this past week included foliar diseases in corn (common rust and gray leaf spot), Japanese beetles feeding on silks and causing defoliation in soybeans, thistle caterpillars, late season weed escapes, and herbicide injury in soybeans.”

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


Category: Crop ProductionTags: crop updatefield agronomistsAuthor: Rebecca Vittetoe

What is a realistic goal for weed management?

Tue, 08/13/2019 - 09:48

The current approach to weed management in Iowa is at risk due to rapid expansion of herbicide-resistant weeds. In order to preserve the efficacy of herbicides two things must happen: 1) adoption of integrated weed management, and 2) shift the goal of weed management from protecting crop yields to minimizing the size of the weed seed bank. The first requires a shift in behavior, the second a change in attitude.

At a recent industry-sponsored field day a speaker discussed his company’s soybean herbicide portfolio and the unique problems posed by waterhemp. He addressed both of the above issues, including the statement that farmers should strive to eradicate waterhemp from their fields. As I walked to the next station I was approached by several of the company reps. My initial thought was 'I haven’t said anything that could possibly upset them', but it turns out they were just seeking my opinion on their suggestion that we attempt to eradicate waterhemp and other problem weeds.  

So what do I think about ‘eradicating’ waterhemp? First, it’s a pipe dream. People involved in pest management long ago gave up on the idea of eradicating established pests.  The goals for management pests at different stages of invasion include: 1) prevention, 2) eradication, 3) containment, and 4) control (Figure 1).  We are long past the point where it is feasible to eradicate or contain waterhemp (or any of our other common weeds).  We shouldn’t forget that waterhemp is native to Iowa and the western Cornbelt.  We can realistically talk about eradicating Palmer amaranth in much of Iowa, in some areas we are probably at the containment stage.

Figure 1.  Stages of a pest invasion and appropriate management goals.

Having said that, I don’t have a problem promoting the concept of waterhemp eradication. Another company has promoted the concept of ‘zero seed threshold’, with the goal of preventing production of any weed seed within a field. I don’t think this is an achievable goal on the scale of today’s agriculture either. However, there is nothing wrong with setting high/unrealistic goals for weed management if it will change behavior. 

The widespread acceptance of late-emerging waterhemp escapes that don’t pose a threat to yield or harvest efficiency is the engine driving the rapid evolution of herbicide resistance in this species.  Anything that can be done to change this behavior will pay long-term dividends.  If promoting weed eradication or zero-seed thresholds can change attitudes towards weed management and promote the adoption of integrated weed management I am all in.

Category: Herbicide ResistanceTags: integrated weed managementherbicide resistanceweed controlAuthor: Bob Hartzler

2019 Iowa State Fair Weed Identification Contest Results

Mon, 08/12/2019 - 14:28

The 2019 Iowa State University Extension and Outreach Iowa State Fair Weed Identification Contest was held on August 9 outside the John Deere Agriculture Building.  Contestants need to identify live samples of weeds of agricultural, horticultural, and natural habitats in Iowa.  Youth are tasked with identifying the first 20 weeds, species that are common across the state. Those competing in the General Division identify an additional 10 weeds, which are less common species. Professionals (weed science professionals and prior winners of the General Division) identify an additional 5 weeds. The weeds for the Professional Division test the contestants’ botanical knowledge. We select some plants that might stretch the definition of a weed (e.g. devil’s claw and devil’s beggarticks).  This year we included cotyledon stage common lambsquarters as many of the contestants in the Professional Division don’t have an agronomic background, and thus might not be familiar with seedlings (we never claimed to be nice).

All weeds remain on display throughout the fair inside the Agricultural Building.

In the Professional Division, Lowell Sandell, a former ISU Weed Science grad student now with Valent, narrowly beat out Josh DeGroot, a current ISU grad student in Agronomy/ABE. Dennis Hartstack, a contest regular, won the General Division.  In the Youth Division, Aiden Anderson finished in 2ndplace for the second year in a row, while Laci Orr moved up from 4th in 2018 to win. Lowell Sandell’s niece and nephew, two of the youngest contestants and first time competitors, finished in 3rdand 4thplace.

Weed identification is a family affair:  Lowell Sandell and Wesley and Aubrey Biegler all went home with ribbons.

Iowa Secretary of Agriculture Mike Naig understands the importance of knowing what weeds are in your fields.

IPTV will feature the contest on the Fair Highlight Show on 
Tuesday night (Aug 13).

Meaghan and I want to thank Erin Jacobson (ISU Biology student) and Dawn Refsell (Valent) for helping make the contest run smoothly.  If you’re at the fair this week, the weeds are on display inside the John Deere Agriculture Building, across the building from the butter cow.  The contest is always held on the first Friday of the fair, and we hope to see you next year.

It was a beautiful day on the fairgrounds for the contest.


Category: WeedsTags: Iowa State Fairweed IDweed identificationAuthors: Bob HartzlerMeaghan Anderson

Predicting the First Fall Frost and Freeze Dates?

Sun, 08/11/2019 - 23:12

When will the first hard freeze or killing frost (equal to or less than 28°F) date be this fall? This is a question a lot of folks are wondering about right now. Over the last few decades the trend for the first frost and freeze dates in the fall has been that they are occurring later in the season when compared to the long-term behavior. The figures below illustrate the average first freeze (32°F) and frost (28°F) dates across the Midwest from 1980 to 2010. While these figures show us what the average freeze and frost dates have been, it is too early to make any predictions about frost and freeze dates for this year yet. 

Median first frost (32°F) dates across the Midwest from 1980 to 2010. Source: Midwestern Regional Climate Center.

Median first freeze (28°F) dates across the Midwest from 1980 to 2010. Source: Midwestern Regional Climate Center.

Category: Crop ProductionTags: frosthard freezeAuthor: Justin Glisan

More and more reports of tar spot on corn

Fri, 08/09/2019 - 15:57

This past week there have been numerous new reports of tar spot within the Midwest, including Iowa (Figure 1). For updates maps, please visit https://corn.ipmpipe.org/tarspot/

Figure 1.  Map of the Midwest showing where tar spot has been confirmed (red) or is pending confirmation (yellow) as of 9 August 2019

Although tar spot is reasonably easy to identify - small, raised black spots on the lower leaves of corn that do not rub off - we are requesting that suspected samples of a few leaves get sent to the ISU Plant Disease and Insect Clinic. Please include the date, county (or nearest township) and information on how much disease is present in the field.  This may include:

  • Percent of plants in the field with tar spot?
  • Which leaves on the plant have tar spot?
  • Approximately how many tar spot occur on each leaf?
  • Does the field have a history of tar spot?  If yes, in what previous years was tar spot observed?

These data will be shared with colleagues in the Midwest who are researching tar spot with a goal of understanding how the disease is spreading. 

Category: Plant DiseasesTags: Tar spot IowaAuthors: Alison RobertsonEdward ZaworskiCrop(s): Corn