Iowa Field Reports: Soybean Gall Midge Emerging, Weed Management Concerns

Reports of soybean gall midge adults emerging, rainfall or lack of rainfall, weed management concerns, and herbicide drift were some of the common issues or concerns that ISU Extension field agronomists saw or heard about this past week. Read on for more about what’s happening in specific regions across the state.

Northwest Iowa

Joel DeJong (Region 1): “In the NW corner of the state, subsoil moisture still is good for the crop. However, daily temperatures in the 90’s and wind speeds over 20 mph are creating stress, particularly on the western edge of the state that is well under half of normal rainfall since planting.

“The rainfall a week ago really helped, but the area on the extreme edge of the state received only about 0.5 inch. More would certainly be welcome. This stress has some corn fields still struggling to get their root systems developed enough to get past the “ugly duckling” stage, while others are really taking off and growing.

“Afternoon leaf rolling isn’t that uncommon right now in corn. Most corn fields did get a post emergence herbicide application on days when the wind wasn’t bad, but many are waiting to apply soybean herbicides when this wind abates.

“Soybean gall midge adults are beginning to emerge – on Monday the first were found in emergence traps at the NW Research Farm. Some experimental insecticide applications have been applied to see if they will help reduce the injury from this pest. Stay tuned!

“Oats are starting to head, lots of hay has been baled, and some alfalfa regrowth was slowed by alfalfa weevil feeding. We’re hoping the rain in the forecast for later this week holds true.”

Paul Kassel (Region 2): “Crop development continues at a rapid pace with our current growing conditions. The corn crop is shading the rows in many fields and the soybean crop is reaching the V2 stage.

“Farmers and applicators are focusing on post emergence herbicide applications in soybeans. However, windy conditions have persisted since Saturday, June 13, and have made herbicide applications almost impossible.”

Central Iowa

Meaghan Anderson (Region 7): “Rainfall variability in central Iowa was significant last week, with some areas at 4+ inches and the majority of the area receiving less than 1 inch. Most corn is past V6, and post emergence herbicide applications are complete.

“Soon we’ll be out keeping a close eye on disease development to determine whether a VT/R1 fungicide application is necessary. Sulfur deficiency symptoms and rapid growth syndrome have been the most common calls in the past week for corn. The first soybean flowers are starting to show up, but most soybean plants have two to four trifoliate leaves.

AgFax Weed Solutions

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“Soybean calls on thistle caterpillars, herbicide options to treat different weed issues, and off-target movement from corn and soybeans have been popular. With post emergence herbicide applications finishing up in soybean fields, remember to scout fields in the week to 10 days following these applications to evaluate weed control.

“This kind of evaluation is essential to determine whether weeds may be resistant, or practices need to change for future years.”


Aaron Saeugling (Region 10): “Field activity has been busy this last week for corn and soybean farmers in SW Iowa. We received some much-welcomed moisture early last week. Parts of Pottawattamie, Cass, Shelby, Harrison and Audubon counties are still drier than normal.

“Consequently, SW Iowa could use substantial rains in the near as there is greater water demand with the lower humidity. Most corn has begun to green up with the recent rain. Sidedressing of nitrogen was a common sight in corn fields this past week, while post herbicide applications were common in soybeans fields with some fields receiving insecticide applications to control thistle caterpillars.

“The most recent news is the emergence of soybean gall midge adults, and I would expect damaging levels in those field with a prior history of this pest.”

East Central, Southeast, and South Central:

Rebecca Vittetoe (Region 8): “Rainfall generally ranged from almost 2 inches to 6 plus inches in a few isolated areas here in EC Iowa over this last week. Corn is mainly V5 to V7 and soybeans are mainly V3 to V4. I have had reports of soybeans starting to flower (R1).

“Do double check crop growth stages with pesticide label restrictions before making pesticide applications. With most post emergence herbicide applications having wrapped up in corn, post emergence herbicide applications are picking up in beans. I have had a fair amount of calls involving herbicide drift from corn fields into soybean fields this past week.

“Other common questions this past week have been on yellow and uneven corn (particularly in my more northern counties), sulfur deficiency, herbicide carryover, and weed management options. On the forage side, most of the first crop hay has been put or is getting put up this week.”

Virgil Schmitt (Region 9): “Rainfall last week was variable in the counties I cover, ranging from less than 0.5 to 2.5 inches. In general, temperatures last week in the counties I cover were normal to three degrees warmer than normal. First cutting hay harvest is nearly complete.

“Most corn fields are at V7 to V9 and look good. However, some fields have areas where plants are showing sulfur deficiency symptoms. Most plants look otherwise healthy and color should improve as root function improves. Some plants with shallow-planted seed are behind plants with deeper planted seed. Post emergence applications are wrapping up.

“I have gotten questions regarding “Rapid Growth Syndrome” (twisted whorls and yellow “flag” leaves) in corn. Soybeans are mostly V2 to V3, and in general, they also look good. Herbicide carryover, herbicide drift, herbicide injury, and dicamba dominated calls last week.”

Josh Michel (Region 11): “Many areas in this part of the state received between 1 and 2 inches of rainfall, with some isolated areas receiving up to 3 or more inches. Between rainshowers, first cutting alfalfa has been put up. Reports of overall quality and quantity have been average or slightly below average for the first cutting this year.

“Forage growth in pastures is quickly slowing down. Corn is generally around V6 to V7, and overall looking very good and continuing to grow quickly. Most sidedressing and post herbicide applications have been completed. Field calls regarding corn have mostly been uneven stands due to compaction.

“Soybeans are mostly V3 to V4, and in general look good. Insect activity, particularly bean leaf beetles, Japanese beetles, and thistle caterpillars have been noted in fields. Additionally, this past week I’ve had calls on herbicide drift in soybeans.”

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