SW MN IPM Stuff 2022 Issue 9

Volume 25 Issue 9 | June 23, 2022

This newsletter and the advice herein are free. You usually get what you pay for.

Crop Weather

Rainfall, air and soil temperatures, degree-days, soil moistures, and other current and historical weather data for the University of Minnesota Southwest Research and Outreach Center (SWROC), a little spot about two miles west of Lamberton, MN, can be found at http://swroc.cfans.umn.edu/weather.  

Hot, dry, and windy in SW MN.  Corn on some of the lighter or compacted ground has started to roll during the heat of the day. Most fields still have good moisture a few inches down, but a moderate rain would be appreciated by many.

Small Grains

Late June through mid-July is armyworm season. Include them in your scouting plans.


On June 22, soybean aphids were found in the soybean foliar fungicide plots at the University of Minnesota Rosemount Research and Outreach Center. Some of these beans were as small as 1st trifoliate. We did not find aphids in the study at Waseca but it’s likely there were some about. The following day more aphids were found in the plots at Lamberton. These were all very small populations, and the infestations are still a long way from yield-threatening.

As the season progresses, larger beans will provide aphids some shelter from excessive heat and winds. On the bright side, we observed the black mummies of aphids parasitized by Aphelinus wasps at Rosemount. For more information see the recent MN Crop News article soybean aphids are beginning to colonize soybean.

Soybean gall midge

It is later than typical, but we finally detected the emergence of overwintering generation adults in SW MN today. Apparently, our emergence cages missed the beginning of the emergence by a few days. While we did not notice any obvious symptoms, soybean stem dissections revealed some white larvae.  You may be interested in seeing this relatively new soybean pest and its injury symptoms in a field situation. We will hold a soybean gall midge field day near Luverne in Rock County, MN on Wednesday, July 13. Details and registration information to follow soon.

If you see soybean gall midge in your fields, please let me know. An entomology graduate student working on natural enemies of the soybean gall midge is looking for fields to sample.

Corn rootworm

As of 6/23  at the SWROC near Lamberton, MN  we were at 625 DD (base 52F) at 2" soil depth and 615 DD at 4".  Peak (50%) egg hatch might occur as early as next week in some fields. You should start seeing some larvae and perhaps root injury by then. We will soon start to get an idea of the extent of corn root injury from rootworms in 2022.

We will be starting to deliver corn rootworm sticky traps next week. Please let me know if you would like to monitor adult rootworm populations in some of your fields, want traps, and haven’t already let me know. The rootworm trapping project is supported, in part, by the farm families of Minnesota corn farmers and their corn check-off investment.

In addition to the reports of true armyworm infestations of corn planted into rye cover crops, an economic threshold population in at least one lodged cereal rye field was reported.

Make sure armyworms are still present before you apply an insecticide. If you didn’t see the recent IPM email on armyworms, here is a slightly more refined version pest alert: armyworm

Happy trails,

Products are mentioned for illustrative purposes only. Their inclusion does not mean endorsement and their absence does not imply disapproval.

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