Volume 25 Issue 11| July 8, 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.
Crops are looking good in most areas I’ve been through, although behind in development in some.
Many received a welcome rain. Some areas received high winds that flattened corn (see also corn rootworm). Depending on weed seedbanks and herbicide programs, areas that had been dry earlier could see some late germinating weed pressure in fields that are slow to canopy.
The recent rains and morning dews might help beneficial fungi temporarily suppress aphid and spider mite populations. Grasshopper populations have remained low in much of SW Minnesota and prolonged wet weather can help suppress populations, especially small nymphs.
Alfalfa
Potato leafhoppers will be the primary concern from now into August. New seeding fields are generally the most attractive. Don’t ignore alfalfa seeded with a companion crop. Don’t overreact to low populations.
Small grains
There are some very good-looking fields out there. The cool early-season weather helped the tillering in late-planted fields.
Soybeans
The forecast weather and soybeans entering reproductive stages should favor soybean aphid population increases. They are present at very low levels in many fields near a buckthorn overwintering source. We should start to get a pretty good handle on the 2022 soybean aphid risk by mid -R3 stage soybeans
In one of the areas at the SWROC where I can usually find large aphid populations first, aphid populations are still low, but we are seeing a large population of mealybug larvae. I am waiting to see how this population develops.
Soybean gall midge
Currently, we are seeing mostly mature larvae and plants with symptoms but where the larvae have left to pupate. The next adult flight should begin soon.
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 can be found at Soybean gall midge field day. Please register by July 11.
Corn
European corn borer
Yesterday I was looking for soybean gall midge in potential native prairie legumes as potential hosts. As reported yesterday I observed large numbers of European corn borer moths in a grassy area adjacent to a Lincoln County corn field. I had not seen a moth population this dense since the 1990s but other grass areas near corn I was in revealed no moths. European Corn borer moths aggregate and mate in grassy areas in and near corn but may mate within larger corn.
To help with the timing of scouting and insecticide applications see the degree-day models for the current univoltine strain and upcoming summer generation of the bivoltine strain of corn borer.
For scouting and management tips see European corn borer in Minnesota field corn.
Corn rootworm
Root injury is visible now with larval feeding ongoing. Currently, there are 1st - 3rd instar larvae present but we have not found pupae in our two Redwood County research sites. It is still too early to know how 2022 and 2021 rootworm injury and populations compare.
Rootworm-injured corn may be most obvious in those areas where wet soils and high winds occurred. Remember to check the roots for rootworm feeding injury before jumping to conclusions.
For those of you trying to float rootworm larvae from corn roots, pay close attention to the specimens to see.
Bits of root or the mostly transparent pot worms might appear similar but, unlike corn rootworm larvae, they lack tiny thoracic legs, a brown head, and a dark spot at the end of the abdomen.
Happy trails,
Bruce