Volume 24 Issue 3 | April 23, 2021
This newsletter and the advice herein are free. You usually get what you pay for.
Nothing to report this week. Typically, freezing temperatures can be more detrimental to hibernating insects after they have become active in the spring. It will take some time to determine if our recent cold snap affected any pests.
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.
- Weather systems conducive to insect migration and insect migrants have been lacking at the SWROC so far this spring. There might have been more insect deposition in those areas that received greater rainfall the past couple weeks. Although migrating insects can “rain out”, a “snow out” might be more challenging.
- The recent cold weather and dry conditions have minimized weed emergence. Common lambsquarters emergence has started. On the southern front, Corey Sinn reported giant ragweed emergence had started.
- The cold weather kept cautious folks from planting. That has changed the last couple days with more corn and soybeans planted.
- I have received photos of germinated corn and soybeans. The SWROC two-inch depth soil temperature was above 50ºF part of each day, and even on the coldest mornings did not drop below 36ºF. Any corn (and soybeans) that were planted should be fine unless planted too shallow. Coarse textured soils may have been a bit colder.
- The topsoil is dry in some fields, with some seed ending up in dry soil. Watch tillage depths and avoid long delays between spring tillage and planting.
Things to watch
Check planting depth and soil moisture often. Depending on the area and the field, you might need to seed a bit deeper to reach moisture. Planting deeper than two inches for soybeans is risky.
If weather remains dry, pre-emerge herbicides may need some help from a rotary hoe.
- The cooperative black cutworm reporting network continues to pick up a very few migrants.
- A single exception would be a trap in Steele County that picked up 6 moths the morning of April 16. That cooperator also reported finding a fungus colony had produced a rather large fairy ring in his lawn – there may not be any correlation between the two events.
- Weekly newsletters, and a revised PDF version of black cutworm facts can be downloaded from: z.umn.edu/bcw-reporting
Cold soils will delay emergence and may give some insects and pathogens a longer time to attack seed and emerging seedlings. However, pest activity can also be slowed when temperatures are very cold. Early-planted corn has been in the refrigerator lately.
Soybean aphid watch
A warm, dry spring and early soybean planting should favor successful soybean colonization. Cold temperatures may have been harmful to any small nymphs on buckthorn and any beneficial insects that emerged from hibernation.
Other soybean pests
Nothing to report. Seedling diseases would be favored by wet soils. Bean leaf beetles will be one indicator of the winter’s and early spring’s effect on insects overwintering above ground.
- Spring growth is 6- 8 inches. Some stems were nipped by frost but should recover.
- It has been hard to find a time where winds are calm and temperatures warm enough to do some effective sweep net sampling but the sweeps that I have taken are almost insect free at this time.
- Cold weather may have affected overwintering pea aphids.
Spring planted cereals are just beginning to emerge. A very few aster leafhoppers and winged English grain aphids in sweeps of a cereal rye cover crop study at the SWROC on April 21. These insects are migrants from areas to the south. Based on the recent stretch of N to NW winds, they have been here for a few days.
Particularly with drier conditions, you might not want to delay cover crop termination for too long.
As always, I appreciate hearing and seeing your observations!