Regional Crop Update: August 12 - August 25, 2020

August 26, 2020 3:45 PM
Blog Post

Rainfall still eludes most of the state of Iowa, and drought has continued to envelope the state, with the driest areas expanding from the west central part of the state. Crops continue to go downhill in the drought and the derecho areas, especially with the warmer temperatures of this week. Other issues noted by field agronomists include nutrient deficiencies and decline of soybeans, twospotted spider mites, silage harvest beginning, and a continuation of the fast maturation of crops due to dryness. Read on for more specifics for what’s happening in different regions across the state.

Northwest Iowa

Joel DeJong (Region 1): “The NW corner of the state remains very dry. In the last several days we have been able to observe many fields beginning to change color. Some neighborhoods and fields show corn husk browning and even some ear drop. You can also see a few soybean fields begin to turn. The hot weather of this week will speed the end of the season. Silage harvest started on some stressed acres at least 10 days ago, and is now the better looking acres are being chopped. Very little disease symptoms have been present, and most insect levels have been relatively low. The one exception has been corn rootworm injury on continuous corn this year. While looking at rainfall data for this region you can see several sites that report nine inches or less since April 1. That doesn’t add up to good yield potential, and hot weather certainly does not help."


Paul Kassel (Region 2): “Corn and soybean crops have started a rapid decline in response to the dry weather. Many of the cornfields have gone from a green color to a brown color in the past few days. Ears of corn in many fields have tipped down and are beginning to dry down. Soybean fields are starting to turn as well. Many farmers were hoping for a late season rain to help out a mostly good looking soybean crop, but it does not look like that will happen.  However, areas of Kossuth, Winnebago and Hancock counties have had some rain in August and are looking pretty good. Spider mites have appeared in a few area corn and soybean fields as well. However, there is not much interest in treatment because of the rapid development of both crops.

corn ears suffering from drought and hot weather
Corn ears shrink in size due to the recent hot, dry weather. Photo by Paul Kassel.


Central Iowa


Meaghan Anderson (Region 7): “Most of central Iowa received less than an inch of rain in the last two weeks, which has not been enough to bring any real relief to the crops suffering from dry conditions and the after effects of derecho. Most of my area is excessively dry and the crops are racing through their late reproductive stages due to that and the recent heat. Corn fields impacted by the derecho continue to mature quickly, with some corn (individual plants) having reached R6 (physiological maturity, black layer) already. Variability will be a significant challenge within and across fields. Most corn is currently somewhere between early R5 and mid R5 (1/2 milkline). Silage harvest has started and is going well, picking up more corn than I expected on acres affected by derecho. Keep updated on storm damage resources on our webpage. Soybeans are rapidly maturing in the R6 stage primarily. Some are apparently lodged or leaning after the derecho and may present a challenge at harvest. Monitor corn fields, particularly those with damage like hail, for ear rots as we continue toward crop harvest."

hailed corn with ear rot beginning
Hailed and damaged corn beginning to show ear rot damage. Photo by Meaghan Anderson.


Aaron Saeugling (Region 10): “Crop conditions in SW Iowa have rapidly deteriorated the last two weeks due to high temperatures and no precipitation. Most corn is now R5 (dent) Silage chopping is currently being done with several reports of 15 to 25% reduction in tonnage this year.  I expect to combines rolling in the coming weeks on thin soils and corn on corn fields. Soybeans had great potential two weeks ago but with no moisture leaf rolling has started daily. Soybeans are in the R6 to R7 stage (full seed to beginning maturity). Forage and pasture conditions north of Hwy 34 are poor with little to no growth in the past 21 to 30 days.  Livestock producers are supplementing cows on pasture. Final alfalfa cutting yields for the year look to be poor."

corn beginning to senesce in SW IA
Drought-stressed corn senescing in SW Iowa. Photo by Aaron Saeugling.

Southeast, and South Central:
Virgil Schmitt (Region 9): “Rainfall last two weeks in the counties I cover was generally less than 1.0 inch except Most of Clinton and Jackson Counties received between 1.0 and 2.0 inches. In general, temperatures the last two weeks in the counties I cover were near normal to a little cooler than normal, as was the southeast two-thirds of the state. Most corn fields are at R5.25 and generally looking good, except for storm damaged fields. Plants vary from not effected at all by the derecho to being destroyed by breaking off below the ear, and everything in between. Occasional sightings of tar spot continue. Soybeans are mostly R5.75. In general, they also look good. Soybeans have generally recovered well from the derecho wind but hail-related issues remain in some areas. Dicamba drift and dealing with derecho-related issues were common topics of discussion the last two weeks."

Accumulated precipitation from August 11 to August 25

Josh Michel (Region 11): “Crops across the region are showing signs of heat stress. Crops on lighter soils are especially showing severe heat stress and are maturing very quickly. No precipitation was recorded last week and many areas have seen less than 0.25 inches of precipitation over the past two weeks. Most of the corn is generally at R5, with a few fields reaching early R6 within the next week. Many fields having firing up to the ear leaf, and I’m seeing a lot of tip dieback and small shallow kernels. Most of the corn related field calls lately have centered around nitrate testing, mycotoxin testing and assessing damaged fields. Soybeans are generally R5 to R6, and surprisingly are still looking ok in most areas despite the warm temperatures and limited precipitation. Soybeans on lighter soils however, are showing signs of heat stress. Most of the soybean related field calls have centered around: nutrient deficiencies, insect feeding, assessing spider mite damage, group 4 herbicide damage and managing late season weed escapes. I’ve also been seeing more fields with Septoria brown spot and frogeye leaf spot. Alfalfa fields and pastures continue to grow very slowly. 3rd cutting in many areas is put up with many farmers reporting considerably less than average quality and quantity of bales. Insect feeding and questions about fall seeding continue to be prevalent.”


Lucas County corn field senescing already due to dry conditions
Lucas County corn field showing drought stress. Photo by Josh Michel.


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

Field agronomist location map


Meaghan Anderson Field Agronomist in Central Iowa

Meaghan Anderson is a field agronomist in central Iowa and an extension field specialist at Iowa State University Extension and Outreach. Educational programming is available for farmers, agribusinesses, pesticide applicators, certified crop advisors, and other individuals interested in...

Rebecca Vittetoe Field Agronomist in EC Iowa

Rebecca Vittetoe is an extension field agronomist in east central Iowa. Educational programs are available for farmers, agribusiness, pesticide applicators, and certified crop advisors.

Areas of expertise include agronomy, field crop production and management of corn, soybeans, and...