7/28/2021 | Volume 24 issue 12
This newsletter and the advice herein are free. You usually get what you pay for.
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 SWROC Weather.
It’s hot and dry, except for areas of the state that are hot and not so dry.
Corn rootworm beetles
Western corn rootworms predominate in many southern MN long-term corn issues. If you have a field that has a rootworm Bt pyramid and is experiencing heavy root damage and/or beetle populations, the correct answer for managing the field in 2022 is probably not to plant a SmartStax Pro hybrid or beetle bomb.
We are also seeing an unusual number of western corn rootworms in rotated corn fields.
After a long hiatus, northern corn rootworm, including extended diapause, populations have made a strong comeback. They will need to be included in future rootworm management.
True armyworms are just one reason that grassy weeds and grass cover crops should be controlled in corn.
Soybean aphid populations, while low in most cases, have tolerated the heat well. Do not count them out as weather cools.
Soybean gall midge 1st generation adults have been active and plant symptoms will continue to increase over the remainder of the summer. The insect has now been detected in Watonwan County, adding to its known distribution in Minnesota.
The hot, dry growing season has led to infestations of two-spotted spider mites in many areas of MN. I suggest you read this MN Crop News blog post: Two-spotted spider mites in 2021 in Minnesota crops? to stay on top of the issue if it is a concern in your area.
Look for stippling (figure 1) as an early sign of mite presence.
- For more information on spider mites on soybean see: Managing spider mite on soybean
- For corn, a 2012 fact sheet PDF is available for download at: Managing two-spotted spider mites in corn.
In addition to spider mites, several insects are taking advantage of the hot dry weather. Potato leafhoppers, Tarnished plant bugs (lygus), and alfalfa plant bugs are all active now. Some SW MN alfalfa where leafhoppers were not managed are looking tough now.
Watch for lygus (Figure 2). Darroll Ike has reported finding some fields with high populations.
Meetings & other topics of interest
- August 10 Crop Pest Management Plot Tour at the SWROC. There will be some stuff to observe! Please pre-register to help us plan ahead. We’re a bit out of practice on in-person events.
- August 17 Cover crops field day. SWROC