Regional Crop Update: July 6 - July 14, 2020

July 15, 2020 7:15 AM
Blog Post

While the western part of the state continues to be on the dry side, parts of central and eastern Iowa got hit with some storms this past week resulting in wind and hail damage. Besides the dry conditions and storm damage, herbicide injury in soybeans, gray leaf spot, potato leafhoppers, and low levels of soybean aphids are some of the issues ISU Extension field agronomists have observed this past week. Read on for more specifics for what’s happening in different regions across the state. 

Northwest Iowa

Paul Kassel (Region 2): “The corn crop is tasseling and silking across much of the area. I would expect the average pollination date will be around July 18 for the area. We are also short on rainfall with much of the area listed on the Drought Monitor as being D0 or abnormally dry. The soybean crop is reaching the R3 or early pod stage. Many farmers and commercial applicators are considering fungicide application to their soybean crop. Low levels of soybean aphids have been found near Sioux Rapids in Buena Vista County.”

Low levels of soybean aphids found near Sioux Rapids in Buena Vista County. Photo courtesy of Paul Kasse.

Northeast Iowa

Terry Basol (Region 4): “Corn and soybeans in general look pretty good in the area. Corn has started to tassel or in the VT stage of growth. Continue to scout for foliar diseases, as some reports of grey leaf spot have been showing up according to Alison Robertson, ISU extension plant pathologist. Tar Spot has also been confirmed in Muscatine, Johnson, Dubuque and just recently Polk County. Soybeans are in the R1 to R2 stages of growth. We received some severe storms that passed through the area on evenings of July 9 and July 11. Some crop damage resulted due to strong winds and hail. From those storms according to the National Weather Service, we received anywhere from 1 to 4 inches of rain for the area. In regards to the hay crop, the second cutting is basically completed.”

Hail damage to a corn field south and west of Shell Rock from a July 11 storm that came through the area. Photo courtesy of Terry Basol.

Central Iowa

Meaghan Anderson (Region 7): “Central Iowa continues to have the “haves” and the “have nots”, with the worst areas receiving less than 0.5 an inch of rain in the last 30 days. I’m hopeful the predicted rains this week will finally bring some to the driest parts of Dallas and Boone County. Corn is basically all pollinating, though development has slowed in dry areas and tassel appearance is still uneven. Most corn is really clean though grey leaf spot and common rust are easily found in some fields. Weed issues are still apparent under the canopy in several fields I’ve walked. Soybeans are R2 to R3 and still look quite nice, though we still see a lot of sunlight on the ground in a lot of 30-inch rows. Big concerns in the last week were the discovery of tar spot in a Polk County corn field (!!!!), more off-target plant growth regulator injury, potato leafhoppers in alfalfa (require treatment) and soybean (require watching), and a small but mighty population of thistle caterpillars in a few Jasper County fields."

Tar spot found in a Central Iowa corn field at very low levels. Photo courtesy of Meaghan Anderson.

Southwest Iowa

Aaron Saeugling (Region 10): “Dry conditions persist over most of SW Iowa, which is causing corn to roll to conserve moisture. Corn is in the late vegetative stages and starting to tassel. The hot conditions are impacting pollination in some fields. Soybeans are coming along with most narrow row fields shading the rows. Hot spots of Japanese beetle feeding is occurring in some fields. I’ve received several calls on poor alfalfa regrowth related to several factors including herbicide carryover, insect feeding, lack of fertility due to dry conditions, and most of all limited rainfall.”

U.S. Drought Monitor showing parts of western Iowa (and little part of eastern Iowa) showing up as a D0 (abnormally dry) or D1 (moderate drought). Map released on July 9, 2020. Source: U.S. Drought Monitor.

Corn showing signs of drought stress. Photo courtesy of Meaghan Anderson.

East Central, Southeast, and South Central Iowa

Rebecca Vittetoe (Region 8): “This last week brought some storms across EC Iowa on July 9 and two rounds on July 11 that caused some pretty severe wind and hail damage in crop fields. The worst damage seems to be north of I-80, particularly in Linn and Jones counties. Most corn fields are either late vegetative or at VT/R1 and soybeans are mainly at R2 to R3. Over this last week, I’ve noticed more gray leaf spot starting to show up in corn fields. Remember this disease favors warm and humid conditions. Double check to make sure what you are seeing is gray leaf spot and that it’s not potentially bacterial leaf streak, as I’ve had a few more reports of that showing up in EC Iowa corn fields as well. Outside of some insect feeding (primarily Japanese beetles) and herbicide injury, soybean fields are looking good.”

Gray leaf spot has started to make its appearance within the last week. Photo courtesy of Rebecca Vittetoe.

Virgil Schmitt (Region 9): “Rainfall last week was variable in the counties I cover, ranging from less than 0.5 inch roughly south of Highway 92 to over 2 inches roughly north of I-80, with locally heavier or lesser rains. Several of the counties I cover sustained wind damage to corn in storms Thursday and Saturday evening and a large swath of hail on Saturday morning severely damaged crops in parts of Cedar, Jones, and Linn Counties. Second cutting hay harvest is mostly complete. Most corn fields are at V16 to VT/R1 and generally looking good, except for storm damaged fields. Soybeans are mostly R2. In general, they also look good, again except storm damaged fields. Grasshopper nymphs can be observed in grassy areas. Herbicide drift, potato leafhopper management in alfalfa, Japanese beetles, and storm damage were common topics of discussion last week.”


Josh Michel (Region 11): “While a few scattered showers did bring up to 0.25 inches of rainfall to parts of SE Iowa, dry conditions continue across most of SC Iowa. With continued above average temperatures and limited rainfall, pastures and alfalfa fields in many areas are showing signs of stress. Second cutting of alfalfa is mostly wrapped up, with many reports of lower than average yields and severe potato leaf hopper damage in some areas. Despite the limited moisture in some areas, corn is generally still looking good with most fields tasseling. In the drier parts of my area it is not uncommon to see corn fields with leaf rolling due to the heat and dry conditions. Farmers should be on the lookout for corn rootworm damage and silk cutting from Japanese Beetles. Soybeans are generally R1 to R3, and despite the limited rainfall are looking good as well. Most of my soybean related field calls continue to be centered around herbicide injury, herbicide drift, and insect feeding. I’m also seeing some soybean fields with 30-inch rows that will most likely not reach full canopy closure. This will most likely result in some late season weed escapes.” 


Alfalfa field with some very severe potatoa leafhopper damage. Photo courtesy of Meaghan Anderson.

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