Iowa Field Reports: Were Too Wet, Now Too Dry

The growing season started off too wet, but now we are going to the other extreme of being too dry in places. According to the U.S. Drought Monitor, just shy of 25% of the state was considered abnormally dry as of July 30.

In addition to the dry conditions, growth regulator damage in soybeans, potato leaf hoppers, gray leaf spot, and concerns about a third generation of thistle caterpillars have been some of the issues or pests ISU Extension and Outreach field agronomists have seen in fields this past week. Read on to see what is happening in specific areas across the state.

Northwest Iowa

Paul Kassel (Region 2): “Development of the late April and early to mid-May planted corn is in the late blister (R2) to the milk stage (R3). The June planted corn is pollinating.  Fungicide applications on corn are wrapping up this week. The soybean crop is in entering the full pod stage of development (R4). Questions and comments on thistle caterpillars have been the main point of conversation with many farmers and applicators. Soybean aphid numbers are light to nonexistent, but farmers are encouraged to check fields for aphid development for the next three weeks.”

North Central Iowa

Angie Rieck-Hinz (Region 3): “Corn is mostly R3 and the earliest planted corn is very early R4 across NC Iowa. The late May-early June corn is approaching VT-R1. Gray leaf spot is becoming more prevalent, but other diseases are at low pressure. Fungicide applications in corn are nearly finished.

“The earliest planted beans are R4 (full pod). I have seen very little disease in soybeans. Soybean aphids continue to be sparse but there are localized areas with heavier pressure. I have seen a lot of questionable control of waterhemp across all the herbicide groups. At this point, I would say weed size was too large when sprayed in most of these situations.”

Central Iowa

Meaghan Anderson (Region 7): “Parts of central Iowa got a much-needed shot of rainfall last week, with some of my northern area getting some more last night (8/5). The eastern part of my area really needs rain as we’ve had only about 2 inches of rain since July 1, but our forecast doesn’t look promising. Some corn is starting to really show some stress and soybean fields are flipping their leaves over fairly early in the day.

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“Most corn is R2 and R3 with some stragglers just starting to tassel and others further along. Soybeans are mostly in the R3 stage, though I am sure there are fields further along that I haven’t seen. Soybeans have been a focus of most of my field calls in the last several weeks, with questions about thistle caterpillars still dominating the conversation (will they be back for a 3rd time?!) and dicamba drift on soybeans coming up second.

“Other phone calls have been about weed identifications, disease development, soybean gall midge, and Japanese beetles.”

East Central, Southeast, and South Central:

Rebecca Vittetoe (Region 8): “We’ve gone from being too wet early in the season to being on the dry side now here in East-Central Iowa. Some rain did come through the area on Monday night (August 5) with the northern part of my area getting more rainfall than the southern part. The crops, pastures, and hay fields have been showing signs of stress. Corn ranges from late vegetative to R3, and soybeans are mainly R2 to R4.

“Continuing to see gray leaf spot as the main disease in corn and very little to no disease in soybeans. On the insect side, seeing lots of Painted Lady Butterflies (adult thistle caterpillars) flying around right now. Potato leafhopper continue to be a problem in hay fields. Additionally, I’ve seen a few soybean aphids, but overall pressure is light so far.

“If the dry conditions persist, keep an eye out for spider mites. Most of my calls and field visits last week were on growth regulator (Group 4) herbicide injury in soybeans. Other calls included fungicide and insecticide applications in corn and soybeans, weed identification, pasture management, and fall seeding of alfalfa.”

Virgil Schmitt (Region 9): “Rainfall last week was mostly zero. Corn ranges from V15 to R3. The June planted corn (V15) is starting to show some tassels and silks. There is a little rust and gray leaf spot. Soybeans are from R2 to R4. There is little disease pressure at this point. Group 4 injury calls are continuing. Oats are mostly turned. Pastures are turning brown.

“Potato leafhoppers continue to be an issue in hay. Inquiries about and Group 4 herbicide injury on soybeans and fungicides on corn dominated calls last week. Other calls included potato leafhoppers, weed management on prevented plant acres, cover crop management, Japanese beetles, and managing new seedings in drought.”

Josh Michel (Region 11): “While some isolated areas in my region did receive up to 1.5 inches of rain, many areas were only lucky to receive around .10 inches. Fields and pastures have started to show more signs of stress. Reports of grasshoppers and potato leafhoppers continue to be found in hayfields. April planted corn is generally ranging around R3, with a few fields possibly reaching R4 by this weekend.

“Late planted June corn may start tasseling later this week. Early planted soybeans are mostly around R3 to R4. Common questions this past week included foliar diseases in corn (common rust and gray leaf spot), Japanese beetles feeding on silks and causing defoliation in soybeans, thistle caterpillars, late season weed escapes, and herbicide injury in soybeans.”


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