Regional Crop Update July 2 to July 10, 2018

July 10, 2018 11:12 AM
Blog Post

The warm conditions continue to push crops along. Across the state we are approximately 140 to 370 Growing Degree Days (GDD’s) head of normal. Most corn and soybean fields are now in the reproductive stages. Excessive moisture, drought, gray leaf spot, Japanese beetles, and off-target herbicide movement seem to be common issues Iowa State University Extension and Outreach field agronomists are seeing across the state this past week. Read on for more information about your region’s crop progress and field conditions.

Northwest Iowa   
Joel DeJong (Region 1): “Rainfall this past week was from half an inch to over 2 inches. That’s down significantly from recent weeks, thankfully. Many corn acres look great, particularly south of HWY 10. Corn is tasseling, although not quite half is at that stage yet. In the northern areas of this region, there remain lots of wet areas that have been lost and many blooming soybean fields that still need herbicide applications. Soybeans in the wet area have been struggling, but recent dry days have helped. Some green snap occurred in storms that rolled through on July 4. Corn rootworm beetles have just started to emerge, and a few bean leaf beetles are emerging, too. There have been a few phone calls and field visits due to dicamba injury in the region.”

Rainfall totals for the past week (July 2 to July 9) across the state of Iowa. Source: 

Paul Kassel (Region 2): "Farmers and commercial applications were hard at work last week with herbicide applications for the soybean crop. Large weed size, windy conditions, and wet fields presented a challenge for many applicators. The pre-emergence herbicide applications on soybean fields performed quite well this season. However, a few fields without pre-emergence or burndown herbicide applications had some 24 to 36 inch weeds that may present a problem to control. There is also some aerial application of urea being applied to help the nitrogen status on some of the corn fields. This is a difficult decision for farmers since the corn fields are extremely variable and not all of the field will benefit from the nitrogen application. Some of the soybean fields are looking better and have somewhat recovered from the waterlogged conditions of June. However, many of the areas in the corn fields that were stunted by the waterlogged conditions have not recovered and continue to appear stressed."

This applicator patiently waits for better conditions to treat this weedy soybean field. Photo by Paul Kassel. 

Northeast Iowa
Terry Basol (Region 4): “Considering the ample amount of rainfall over the past couple of weeks in Northeast Iowa, corn and soybeans are holding their own. According to the Iowa Mesonet, we received about 4.3 inches of rain from June 24 through July 8 at the NE Iowa Research and Demonstration Farm near Nashua. Most of the corn in the southern two-thirds of my territory has reached the R1 (silking) stage, with the rest of the corn throughout the territory in the mid to late vegetative stages (depending on planting date). I have seen some Physoderma brown spot showing up in corn fields last week due to favorable weather conditions. Green snap in corn fields has also been observed, particularly since the storm event on June 30th, which produced up to 50 – 60 mph winds across much of my territory. Soybeans are generally in the R1 (open flower at any node on the main stem) to R2 (open flower at one of the two uppermost nodes with a fully developed leaf) growth stage throughout my territory. Septoria brown spot remains to be found in the lower canopy; continue to scout and monitor to determine if it moves into the mid-canopy. There have been some reports of Phytophthora root and stem rot in soybean in the North Central and Northeast parts of the state due to the excessive rainfall and prolonged periods of saturated soils. So far, soybean aphid levels remain low from the weekly counts that ISU field agronomist Brian Lang conducts during the growing season.  

Southwest and West Central Iowa
Mike Witt (Region 6): “West Central Iowa received a break from the rain this last week with in general zero to 1 inch of rain falling on July 4. Corn is progressing well with fields anywhere from tasseling to brown silks. The current weather conditions with the warm nights are very favorable for quality pollination of corn. Soybean fields are greening up and canopies are starting to close. Final herbicide sprayings should be getting completed with soybeans, if not done, due to growth stages being mostly in R2 or full bloom. Diseases in corn are few with a little gray leaf spot and some Physoderma brown spot reported. So far this gray leaf spot is staying below the ear leaf and not progressing higher in the canopy so it is of lesser concern. Aerial fungicide applications are occurring around the area so be aware of surroundings and low flying planes. Japanese beetles are still the only insect flushes being reported with scattered small reports of bean leaf beetle or corn rootworm beetles seen. Remember, dicamba damage symptoms to crops occurs 10 to 14 and sometimes up to 21 days after application.”

Physoderma brown spot lesions on the midrib of a corn leaf. ​​Source: Farmers Guide to Corn disease IPM 76. 

Central, East Central Iowa, Southeast, and South Central:
Meaghan Anderson (Region 7): “The last week brought a welcome break from most of the rain in central Iowa, which has hopefully allowed some of the flooding to recede across fields and let the crops dry their 'feet' (roots) off a little. I've been told that with the break from rain, many of the soybean fields previously showing yellow patches have begun to green back up and look much healthier. Soybean rows have closed or are nearly there for being closed. Most corn and soybeans are now in reproductive stages, and the cooler weather at the end of last week was a welcome change for both me and surely the crops as well. Most corn looks to be pollinating beautifully across the area, but I have noticed some unevenness across fields persisting from earlier in the season. While we've been keeping a close eye out for advancing diseases, gray leaf spot is not as bad as I would have expected given the weather we've had. It's important to monitor fields and determine whether it is moving up in the canopy to the ear leaf and above. Some Japanese beetles have been noted eating silks, primarily along field edges, but I have yet to see a field that meets threshold. Now through the end of the growing season is a great time to monitor for weed escapes, manage the ones you can, and take good notes for this fall and next spring. Phone calls across Central and East Central Iowa continue to be on herbicide drift and yellow or nutrient deficient crops.”

Rebecca Vittetoe (Region 8): “The dry spells continues in this part of the state. The majority of corn and soybeans are now in the reproductive stages. A lot of the corn has already pollinated or is pollinating right now. As far as any issues go, I’ve been seeing some gray leaf spot in corn, but for the most part it seems to be staying in the lower canopy. Continue to monitor fields to see if moves up in the canopy to help determine if a fungicide application is warranted. I’ve also seen some minor defoliation in soybeans due a variety of pests including grasshoppers, Japanese beetles, and even some green cloverworm. On the forage side, we have definitely hit that summer slump and the dry conditions are not helping. Continue to check alfalfa fields for potato leafhoppers.”

Checking on pollination in a corn field. Silks still attached indicate that those ovules have not yet pollinated. Photo by Rebecca Vittetoe. 

Virgil Schmitt (Region 9): “Most of the territory I cover received no rain during the last seven days. The far southeast corner received between 0.5 and 1.5 inch and the northern most area received 0.25 of an inch or less. Corn is mostly V17 to R1 and generally looks good. There is a little gray leaf spot showing up in corn fields. Soybeans are mostly at R2 and also generally look good. Japanese beetles and malformed soybean leaves dominated calls last week.”

Josh Michel (Region 11): “The dry spell continues in this part of the state. While the dry conditions have allowed for farmers to make their second crop of hay and also start to combine oats and rye, unfortunately the dry conditions are really taking a toll on pastures and forage crops. Pastures and forage crops that were previously looking ok, are showing more signs of drought stress. Overall, corn and soybean fields are looking very good considering the limited amount of rainfall that we’ve received.  Soybeans are mostly R2 to R3 and corn is mostly R1 to R2.​​ Minor Japanese  beetle feeding and other insect defoliation have been observed in soybeans. Gray leaf spot and Physoderma brown spot can be found in corn fields, but so far these diseases are not progressing too quickly. If the dry conditions continue to persist, spider mites will be a pest to be keep your eyes open for in soybean and corn fields. Also, conintue to scout for potato leafhoppers in alfalfa. Calls last week mainly consisted of pasture management questions and herbicide group 4 or plant growth regulator off-target movement.”

Some minor skeletonization or defoliation of soybean leaves caused by Japanese beetles. Photo by Rebecca Vittetoe. 

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. 



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...