Iowa crop update July 26 to Aug. 1

August 1, 2016 5:08 PM
Blog Post

Iowa State University Extension and Outreach field agronomists report crop conditions in your area of the state.

Joel DeJong: It’s been pretty dry in the very western edge of the area, with less than 2 inches of rain in the last six weeks. Corn has been rolling every day the last 10 days in that area. However, conditions improve as you head east from there. Corn is R3 and soybean is probably R3-R4. Aphid numbers remain low.

Paul Kassel: There was not much rainfall this past week. However, there have been some 3.5-inch to over 6-inch rainfall totals for July in my area. Corn is in the late milk stage to early dough stage. Fungicide applications are nearing completion, although there is little corn leaf disease present in the fields. The soybean crop is R3-R4 stage. Fungicide applications are nearing completion. Soybean aphid numbers have been very low to date, but there are a few reports of aphid numbers reaching 100+ per plant. 

Brian Lang: Most soybeans are R3-R4 stage, and most corn is currently in the R2-R3 stage. Crop growing conditions are quite good in northeast Iowa. If conditions were stressful during R2–R3 stages, we would see yield reductions from loss of kernels (kernel abortion via tipping back of the ears). Once corn reaches the R4 stage, kernel number is established and yield reductions caused by stress would be from a decrease in kernel size. In corn, we’re still not finding much for leaf diseases except for common rust. In soybeans, we’ve seen bacterial blight, Septoria brown spot, Cercospora leaf blight, and Sudden Death Syndrome (SDS), which is showing up quite nicely in some fields. The continuation of a wetter than normal summer should enhance SDS disease development.

Mark Johnson: Early planted corn is in the R4 stage, with the later planted crop at R2. Soybeans are around R4, as well. There has not been very much insect or disease activity in central Iowa, but I have had a few calls on weeds. I continue to see fungicide applications, even with low insect and disease pressure. I have not been in a field yet of corn or soybeans that warrants a fungicide and/or insecticide applications.

Southwest and West Central
Aaron Saeugling: Corn is in the R2-R4 stage and looks good. We have observed some fungicide application being made in the past few weeks. Disease and insect pressure is rated low at this point. Some ears indicate stress factors during pollination, mostly due to high temperatures and planting issues earlier in the growing season. Soybeans are in the R2 to R4 stage with good growing conditions. There has been limited disease pressure, and some bean leaf beetle feeding along with isolated reports of Japanese beetles. Some fields have waterhemp pressure and others have scattered weed issues. 

Michael Witt: The west central Iowa area was mostly dry over this past week except for an area in Shelby County and Crawford County that received rainfall, totaling at around .5 to 1.5 inches on July 27. Both corn and soybeans are in good condition, with maturities being around R3-R4 for both crops. Continued, timely rains will be important during this phase of crop growth and development, as pods are setting and filling on soybeans and kernels are developing on corn ears.

Fungicides applications are still occurring for many fields even though the pressure for disease is low as compared to other years. Disease scouting around the area has seen some rusts and grey leaf spot in corn, and a few instances of SDS starting to appear in soybeans. Continued scouting and reporting of disease problems greatly helps all farmers in the community with managing possible issues. Notable insects that have been observed in this area are corn rootworm beetles, Japanese beetles, and grasshoppers. Corn rootworm beetles have been spotty in their numbers with some seeing large volumes and others very few. As corn matures, corn earworms will start to become more prevalent, so be aware and check for infestations. With the forecast of rain and hot and humid conditions returning to Iowa this week, corn and soybeans will continue on their current track of growth and development.  

South Central, Southeast, East Central
Rebecca Vittetoe: Corn and soybeans are moving right along in south central and southeast Iowa. Corn is mostly in the R3 (milk) to R4 (dough) stage, and soybean are mostly in the R3 (begin pod) to R4 (full pod) stage. The most popular questions I’ve been getting is whether to spray or not to spray a fungicide or a fungicide + insecticide. And “when is it too late to spray?” Just because your neighbors are spraying doesn’t mean that you need to. Instead, scout to see if you are seeing diseases/insects showing up, what diseases/insects, and how much. I answered these questions in my recent newsletter: Crop Connection Newsletter.

Gray leaf spot seems to be a common disease showing up in corn, and within the past week I’ve started to see soybean fields with Sudden Death Syndrome starting to appear.

Meaghan Anderson: Corn in east central Iowa is in the R2-R4 growth stage; it looks quite good with little disease pressure and few insects in many fields. Soybeans are looking great as well, with most in the R2-R4 growth stages. Some areas in soybean fields are beginning to show symptoms of sudden death syndrome (SDS). Anyone scouting should split the stem to make sure that the issue is SDS and not brown stem rot (

Virgil Schmitt: Last week we had an inch or less of rain, with most places receiving virtually none. Corn is R3-R4 and soybeans are also R3-R4. Concerns have been weed escapes and fungicide applications in both corn and soybean. Soybean Sudden Death Syndrome is also showing up.

Find your local ISU Extension and Outreach field agronomist here!

Related articles:
Iowa Crop Update July 18 to July 25