Iowa: New Counties Confirmed with Soybean Gall Midge in 2022

A number of labs within the Midwest have been monitoring the distribution of soybean gall midge in Iowa since 2018. Final yr, we sampled many counties in western Iowa however solely confirmed three new counties. This yr, we targeted on the counties simply east of the distribution in 2021 and had been capable of verify eight new counties in Iowa that had soybean gall midge: Humboldt, Kossuth, Palo Alto, Pocahontas, Polk, Ringgold, Warren, and Webster (Determine 1).

Iowa now has 42 counties confirmed with soybean gall midge, practically half of the state. To see the distribution in different states, go to our regional web site (155 complete counties in 5 states).

Within the newly confirmed counties, we stopped in random soybean fields on the western half of every county. We prioritized soybean fields that shared a border with a cornfield (see rationalization beneath).

As soon as we discovered a really perfect area, we checked crops on the edge (subsequent to corn) for useless/dying crops, wilting, or black lesions on the base of the stem. If lesions had been discovered, we pulled the crops and opened the lesions to substantiate that soybean gall midge larvae had been inside (Photograph 1).

The fields we confirmed larvae on this yr had low infestation ranges – we might solely discover a couple of crops with black lesions and there have been lower than 5 larvae inside. Be certain to verify area edges for useless crops, wilting, and black lesions, then break the stem open to substantiate that soybean gall midge larvae are inside. Infestations in new counties could also be troublesome to identify due to this low incidence or be confused with fungal pathogens.

There aren’t any confirmed administration techniques obtainable for soybean gall midge presently. Pesticides are probably ineffective as a result of the larvae feed inside the stem and are troublesome to achieve. We suggest monitoring for larvae throughout July and August, particularly in soybean fields which have a border with a area the place soybean was planted the earlier yr.

For extra info on soybean gall midge, learn this ICM encyclopedia article. If you’re all for real-time updates on soybean gall midge exercise and distribution in 2023, be part of the Soybean Gall Midge Alert Community or the Iowa Pest Alert Community.

Determine 1. Counties with soybean gall midge in Iowa (as of twenty-two August 2022). Orange highlighted counties had been confirmed in 2022. Grey counties had been scouted however not confirmed. Click on Picture to Enlarge

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Photograph 1. Black lesions kind on the base of the plant close to the soil line (left) on account of larval feeding damage. When the lesions are opened, larvae might be discovered inside. Right here, you may see the orange, third instar, by way of the lesion (proper). Photographs by Ashley Dean. Click on Picture to Enlarge

First detection scouting suggestions:

Midges overwinter in soybean fields and start grownup emergence in mid-June. They may search out soybean to put eggs however aren’t thought of long-distance flyers. New area detections are nearly at all times confirmed alongside the sting rows. If these crops are clear, don’t hassle sampling the sphere inside.

• Begin wanting on the edge rows which are adjoining to a area that was soybean the earlier rising season (probably now a cornfield).
• In vegetative soybean, concentrate on discovering wilted or stunted crops. Pull the crops and break open the stem simply above the soil line to seek out feeding larvae.
• Typically surrounding crops will fill within the gaps of useless crops or get changed by weeds.
• In reproductive soybean, half the cover and search for darkish lesions on the stem simply above the soil line. In some instances, infested crops turn into brittle and simply break off from the roots.
• Later within the season, infested and useless crops might be held up by surrounding crops.

In case you discover soybean gall midge in a county not indicated as infested in Determine 1, attain out to your area’s extension area agronomist or the authors for affirmation.