SW MN IPM Stuff 2016 Issue 9

Volume 19, Issue 9 - June 17, 2016

This newsletter is also available in a print-friendly pdf format: SW MN IPM Stuff 2016-09

This newsletter and the advice herin 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 Southwest Research and Outreach Center (SWROC), a little spot about two miles west of Lamberton, MN can be found at the SWROC weather webpage.

We have received 667.5 degree-days (base 50°F) and 7.15 inches of rainfall May 1 - June 16 ,both above long-term average. There were 105 degree-days (base 50°F) accumulated from April 11-30.

The largest corn on the SWROC is averaging V8. Some big rains and a few tornados punctuated the 2016 spring. There was some vertically challenged corn after the Tuesday storms, but the stuff I windshield survey everyday has come back up. As soils have dried, corn health has improved. We are seeing wrapping of some area corn because of rapid growth. Some area fields have already closed a good canopy. There a going to be some "yield holes" in many SW and SC MN fields because of the excessive rain.

ipm09aThe largest soybeans here, planted April 13, are at V5 stage and branching where they have room. Group 0 soybeans planted the same day have been flowering for a week, and early-planted mid group I soybeans have just barely started to bloom. Over on the eastern front, "Deep Throat" also reported early-planted group I soybeans starting to show a few blooms.

Remember, late-planted soybeans will often begin to flower as smaller plants than those planted earlier. Reproductive stage soybeans do not typically respond to herbicide or other forms of defoliation with increased yield.

Spring wheat and oats are heading - flowering depending on planting date and variety.

As always, pay attention to label restrictions on pest stage and crop growth! Expect some late season weed pressure on late-planted and re-planted areas because of slow and smaller crop canopy.

Yellow soybeans

It may not be iron deficiency chlorosis (IDC), root rots, or even temporary yellowing from an herbicide application that is causing the problem. I visited a Redwood County soybean field that had IDC symptoms. Female soybean cyst nematode (SCN) cysts were starting to emerge from the roots and were easy to find on V1-2 SCN resistant soybeans. All SCN resistant soybeans are not equally resistant and SCN populations in some fields are virulent (can infest and reproduce) on one or more SCN resistance sources (e.g. PI88788 or Peking). Later planting and warmer soils can produce SCN symptoms on smaller plants. Symptoms on SCN resistant varieties indicate a problem with level or source of SCN resistance.

European corn borer

1st generation black light trap captures have been low. 2016 results are posted once a week and can be found at: https://www.vegedge.umn.edu/moth-data/ecb-info

Scout the tallest corn without an above-ground Bt trait first. There should be some shot hole feeding damage started.

The univoltine biotype will occur in July and may be more pronounced, particularly in WC and NW MN.

Soybean aphid watch 2016

Aphids have started to colonize a few more areas but numbers remain well below economic threshold here. Unless your fields have a much, much higher aphid population than I have been seeing, save the insecticide and some money for now.

The first SW MN aphids for 2016 are now being assayed for pyrethroid insecticide resistance.

Grass carrying wasps

Last week on Twitter, I mentioned black wasps on the flowers of some Brown County leafy spurge. Turns out, some similar insects have been plaguing my wife for a couple of weeks this spring.  She had been finding dead wasps in one of the rooms and asking me what they were. Once she found a live one between the window and screen, I decided it was time for me to spring into action. When sunlight hit the wings of the thread-waisted wasps, it revealed a beautiful purple-black sheen to the wings that would look good on any hot rod. After I noticed some bits of grass stuffed in the window frame the ID was easy.

ipm09bThese were indeed thread-waisted wasps in the family Sphecidae. The grass bits indicated they were in the group known as grass-carrying wasps. These wasps create nests with bits of grass they carry into abandoned tunnels and burrows made by other insects. The females provision nests with insects such as tree crickets and pupae over-winter. The screen track in our window and gaps under the brick molding apparently made a suitable substitute for an insect tunnel.

The wasps aggravating my wife were emerging from last fall's pupae. A quick double-check on the internet let me state that these were probably in the genus Isodontia. I pointed out that they were harmless and they were from last summer's larvae.

"How did they get inside the house?" - They probably found a gap between the window frame and the plaster.

"How do I get rid of them?" - Once they are done emerging that'll be it. You've only seen a few of them. They're harmless so relax quit worrying about them. I was impressing myself with my detailed knowledge of the subject; some of it new-found from the internet.

"There's a gap at the top of the screen. Will more get in this year?" - I wouldn't worry about it. If they do...heck, they might even keep the cricket population down. If you're that worried about it, you could fix the screen.

I never did find out what hit me.

This is a mostly true story but no actual wasps or IPM folks or thier families were harmed during the telling.

Upcoming Events

SWROC Organic Field Day July 6 and Organic Field School July 13

Ag Production Field Day July 11 

Field school for ag professionals July 26-27

ipm09cButterflies

2nd generation red admirals and alfalfa caterpillar adults are common now in SW MN.

Fortunately, we can still find a few caterpillars of the monarch butterfly in SW MN.

Nowadays, I have to look at a lot of milkweed plants to find a caterpillar but then...I did when I was pulling milkweed out of soybean fields years ago too!

Happy Trails,

Bruce Potter