Regional Crop Update July 9 to July 17, 2018

July 18, 2018 11:18 AM
Blog Post

This past week brought drier conditions across the state. Northern Iowa appreciated the chance to dry out some, but parts of southern Iowa could really benefit from some much needed rain. Check out what Iowa State University Extension and Outreach field agronomists have been seeing in fields across the state over this past week.

Northwest Iowa   
Paul Kassel (Region 2): “Herbicide application to the soybean crop is wrapping up. Weed control with the dicamba products labeled for soybean appear to be working well; however, waterhemp in some of the fomesafen (PPO-inhibitor) treated fields are starting to recover and are not dying. The damage from the waterlogged conditions from the heavy rains in late June is still evident. While there are a lot of corn fields that are looking better, there are still areas in corn fields that have not recovered. The soybean crop on the other hand appears to have recovered from the waterlogged conditions fairly well in most cases. A few farmers replanted some drowned out areas last week. The mid-May planted soybean fields are approaching the early pod stage (R3).”


Corn stunted from waterlogged conditions that is in the V14 stage, compared to the rest of the field which is at VT. Photo by Paul Kassel.  

Northeast Iowa
Terry Basol: (Region 4): “Weather was very favorable for crop development this past week. According to the Iowa Mesonet, we received about 2.5 inches of rain from July 9 through July 14 at the NE IA Research and Demonstration farm near Nashua. In general, most of the corn in my territory has reached VT, with the exception of the late planted corn. Some corn in the southern part of the territory is in the R1(silking) to R2 (blister) stage of development. Overall, soybeans are in the R2 (full bloom) to R3 (begin pod) stage. According to the most recent Iowa Crop Progress & Condition Report  from the National Agricultural Statistics Service (NASS), eight percent of the soybeans in NE Iowa are setting pods. Soybean aphid levels continue to remain very low for NE Iowa. Continue to scout both corn and soybeans for foliar diseases.”

Southwest and West Central Iowa
Mike Witt (Region 6): “West central Iowa received some rain between 0.25 of an inch to 1.25 inches last week. This rain pattern has helped the crops continue to grow well with adequate moisture in most of the region. The cooler temperatures expected during the end of the week will help slow down some of the pollination and growth rate of the plants. Corn is anywhere from having pockets of tassels still emerging on later planted varieties to pollination complete and blister kernels starting to form. This spread is normal and with the forecast, the weather will be a good environment to finish the corn pollination season. Soybean fields are mostly closed canopy and are at the R2 growth stage. Fungicide spraying is in full swing across the area with many airplanes flying. Remember to scout your fields and make good economic decisions because disease has been very spotty so far in western Iowa with not all fields needing a fungicide. Insect populations are also spotty with Japanese beetles, grasshoppers, and corn rootworm beetles being reported. As a tip, there is usually more insect damage, especially from Japanese beetles, at the field edges as opposed to the middle. Be sure you hit your damage thresholds before spraying with tight margins this year. When soybeans are in the reproductive stage, the threshold for spraying for insect defoliation is if there is 20% defoliation across the whole field. Herbicide applications pretty much wrapped up last week, so if scouting for dicamba damage remember it occurs 10-14 up to 21 days after application.”


Soybean defoliation injury is often over-estimated. These leaves show various levels of soybean defoliation. Source: University of Nebraska Extension.

Central, East Central Iowa, Southeast, and South Central:
Rebecca Vittetoe (Region 8): “Corn is mainly in the R2 (blister) to R3 (milk) stage and soybeans range from R2 (full bloom) to R4 (full pod). Overall, crops look pretty good, but I was seeing some corn fields in the drier areas that were really starting to show signs of stress towards the end of last week. Gray leaf spot seems to be the biggest issue in corn right now. In some fields, the gray leaf spot is moving up in the canopy and fields are needing to be sprayed. If you haven’t recently checked your fields, I encourage you to do some scouting. Not seeing much for disease pressure in soybeans. On the insect side, potato leafhoppers continue to be a concern in alfalfa, and I also had a report of some armyworms in an alfalfa/grass hayfield. Other insects to be looking for include adult corn rootworms and first generation bean leaf beetles. On the weed side, I am seeing weed escapes appearing in fields. Now is a great time to walk fields and take care of some of those escapes, but also consider what caused those weeds to escape. Calls on off-target dicamba movement have picked up more in the last week.”

Virgil Schmitt (Region 9): “Rainfall amounts were generally less than 1.5 inch during the last week. Corn is mostly at R2 to R3 and generally looks good. Gray leaf spot took off last week in some fields and planes and helicopters started spraying in earnest. Soybeans are mostly R3 (begin pod) and also looks good. There is some Septoria brown spot in the mid canopy in some soybean fields. Off-target dicamba movement concerns and Japanese beetles dominated calls last week.”

Josh Michel (Region 11): “Some much needed precipitation provided some relief across the region, but rainfall amounts were spotty and varied from 0.1 inch to 1.5 plus inches in isolated areas. Pastures and hayfields are slowing down and showing more stress with the persistent dry conditions. Over the last week, oat harvest has wrapped up. Most corn fields are at R2 (blister), with a few fields at R3 (milk). Considering the lack of moisture, in general corn fields in the region are looking ok, but some fields are showing more signs of stress. Soybeans are mostly at R2 (full bloom) to R3 (begin pod), with some of the earlier planted fields at R4 (full pod), and in general they are looking good. Calls last week consisted of pasture management questions, late season weed management concerns, minor defoliation in soybeans, gray leaf spot, corn earworms, and group 4 herbicide damage in soybeans. Looking ahead, keep an eye open for spider mites, especially if the dry conditions persist.”


Corn earworms found feeding on the tip of some field corn in Appanoose County. Photo by Josh Michel. 

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


Map showing the regions and counties field agronomists cover.

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Rebecca Vittetoe Field Agronomist in SC Iowa

Rebecca Vittetoe is an extension field agronomist in southeast/south 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, so...