Crop Update July 24 - August 2

August 2, 2017 7:52 AM
Blog Post

Rainfall continues to be scattered across the state. According to the U.S. Drought Monitor, 64% of the state is abnormally dry, 34.7% is in a moderate drought, and 1.6% is in a severe drought. ISU Extension field agronomist share what they are seeing in their respected areas across the state.

U.S. Drought Monitor as of July 25. Source:

Northwest Iowa

Joel DeJong (Region 1): “Rainfall was scattered again last week, and the driest areas received about .75”. Cooler temperatures and some rain has helped improve their appearance for the short run, but the driest areas are again showing stress, even with cooler days over the weekend. At the same time, some areas that have received more rain since May 20 are hanging in there well and look pretty good in the field. The range of yields in corn this fall will be quite wide. A few of the worst fields are beginning to be harvested for silage. In the middle of the region I cover, the beans are not really closing 30” rows. More rain is needed. There has been a few calls about spider mites, but they don’t look widespread at this time. Aphid numbers remain low, but can be found much more easily. Off-target dicamba injury calls continue, and last week might have been the most I have received in a week. Recovery is very slow in the areas where moisture is limited."

A field injured by an application on June 20 is still not showing a significant return to normal leaf shape after 40 days, and the “brown gaps” between rows is wider when you are closer to the neighboring field where the herbicide originated. Photo by Joel DeJong.

Paul Kassel (Region 2): “Most of my area has made an appearance on the Drought Monitor either as abnormally dry or moderate drought. Much of the corn is in either R2 (blister stage) or early R3 (milk stage). Most fungicide applications have been completed. The soybean crop is the R3 (early pod stage) with some early plant soybean fields into the R4 (full pod stage). Soybean aphids are more common. I encourage farmers to check their fields for soybean aphids since soybean aphid yield damage is greater with dry soil conditions. Fields affected by dicamba movement have been very slow to recover. This is likely due in part to the continued dry weather. Farmers who have soybean fields affected by dicamba movement are concerned about the yield impact from these conditions.”

Soybean plant with cupped leaves from dicamba movement on 7 nodes in Buena Vista county. Photo by Paul Kassel.


Mark Johnson (Region 7): “The nine county area I serve is all in either abnormally dry or moderate drought. Much of the corn is in either blister stage (R2) or milk stage (R3).  Virtually all the soybean are in either full bloom (R2) or beginning pod (R3). From what I have seen most soybeans are in R2. Rainfall continues to be far behind for June and July.  However crops still look fairly good due to beginning the season with a good amount of water in the soil and the fact that roots were never saturated during June so developed extensively. Pollination went well considering how hot and dry it was during pollination. The high humidity kept the silks from getting desiccated and so the ovule fertilization was able to be completed. There is some tipback of kernels. Tipback will occur for up to about two weeks following pollination in any given field if conditions aren’t favorable. Both disease and insect issues have been at a very low rate and severity.  I have found slight infestations of common rust and slight feeding by grasshoppers. I continue to go on dicamba issues calls and Palmer amaranth in CRP/Pollinator calls.”

Grasshopper feeding on a corn leaf. Photo by Mark Johnson. 

A few common rust pustules found on a corn leaf, but overall disease pressure is fairly low. Photo by Mark Johnson. 

Southwest and West Central:

Aaron Saeugling (Region 6): “Corn is in the R2 to R4 stage in most of SW Iowa. Welcome rain was received in some portions of SW Iowa last week with amounts varying from nothing to over 2 inches reported. In the dry areas moisture is still needed. This will help kernel fill. Planes were still flying fungicides on in corn last week. There are some foliar diseases present, but overall disease pressure is at low levels. Soybeans are in the R1 to R3 stage and are tolerating the dry weather better. There have been some sightings of aphids as well as hot spots of Japanese beetles. Still getting drift reports, which also continues to be a topic of conversation. Alfalfa and hay conditions declined due to dry weather, even in areas that have received rain. More rainfall is needed to allow the pastures to recover. Cooler temps are forecasted, which will help stressed pastures.”

Southeast and South Central: 

Rebecca Vittetoe (Region 8): “We continue to be very dry in this part of the state. Rain was pretty spotty and limited again last week, with rainfall totals ranging from nothing to 0.5 inches. Corn is in the R2 to R4 stage. With the lack of rain, we are seeing quite a bit of tipping back on corn ears and also firing of plants. In some areas, farmers are starting to green chop or are looking to start doing silage. Nitrate levels can be high in drought stressed corn that is stunted or not growing normally. It is important to test and see if nitrate toxicity might be a problem. Ensiling will help to lower the nitrate levels. Soybeans are mostly in the R2 to R3 growth stage. As we enter the pod set and seed filling stages,the soybeans could really benefit from a rain. On the pest side, seeing little to no disease pressure in corn or soybeans. Spider mites are a pest to keep an eye out for though. Continuing to receive phone calls on Group 4 herbicide drift in soybeans. Pastures and hay fields look pretty tough due to the dry weather.”  

Not an uncommon site to see tipping back on corn ears this year. Photo by Rebecca Vittetoe. 

Meaghan Anderson (Region 9): “Corn in east central Iowa is mostly in the R2 to R3 growth stage. Planes are flying to apply fungicides and possibly some insecticides, despite relatively low disease pressure across much of the area. Pollination looks to have gone well in most fields; plants will continue to fill kernels now, though some may be aborted if conditions are not great for grain fill.  Soybeans are also mostly in the R2 to R3 growth stage across the area. Japanese beetles should be clearing out of fields soon and most fields are relatively clear of any disease. It is not difficult to find spider mites in soybean fields in my southern counties and given the immediate forecast of little chance of rainfall, keep monitoring for these insect-like pests. Erin Hodgson’s ICM article is helpful to make management decisions. Waterhemp is peeking above many soybean canopies and will produce significant seed. Suspect PPO or glyphosate-resistant populations can still be sent to the University of Illinois for testing.”

It's not uncommon to be seeing waterhemp peeking above the soybean canopy. Photo by Meaghan Anderson. 

Virgil Schmitt (Region 10): "Rainfall has been sparse with most places receiving less than an inch of rain in the last week. Long-term lack of rainfall continues to be an issue generally along and south of Highway 92. Corn and soybeans are both R2 to R3 and look quite healthy. Common rust can be found in some fields. There is a fairly constant drone of airplanes making applications of insecticides and/or fungicides. There has been a new find of Palmer amaranth in Clinton County. It looks like eradication will be a community-wide project. Items from last week include Palmer amaranth, Japanese beetles, bean leaf beetles, spider mites on a few soybean fields, fungicides, and Group 4 herbicide exposure to soybeans.”

Map showing rainfall totals for Iowa over the last week. Source:  

Find your local ISU Extension and Outreach field agronomist here!


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...