SW MN IPM Stuff 2019 Issue 2

Volume 22 number 2

05/10/2019

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

A print-friendly version of this newsletter is available to download here: PDF iconSW MN IPM STUFF 2019-02

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 SWROC Weather.

Chart comparing the springs of 1993 and 2019Figure 1. A feeble attempt at optimism.


Yes, it has been a cold wet spring. Minimal degree-days (Base 50ºF) have accumulated so far this spring, but I have received a picture of early-planted corn emerging. 

In much of SW MN (and other areas), little corn has planted, including the SWROC.

Although it is much wetter than 1993, it has been a couple degrees warmer (Figure 1). There is quite a bit more tile in the ground since 1993 though. I hope we will see improved weather for the remainder of 2019 planting and beyond. 

Black cutworm

The latest UMN Cooperative Black Cutworm Trapping Network Report (#4) is available at UMN Cooperative Black Cutworm Network 2019-04. You can find previous reports and additional information on scouting and managing this insect at UMN black cutworm reporting network.

This spring, there have been several flights of migrating black cutworm into the state. Based on the size of some of these flights, it will be prudent to pay attention to fields without the Herculex I or Viptera above-ground Bt traits during early-season corn scouting.

Soybean gall midge

MN is one of several states that are working to understand the distribution and biology of a new insect pest of soybeans, the soybean gall midge, Resseliella maxima Gagné.

Soybean gall midgeFigure 2. Soybean gall midge


Infestations of this insect can cause death of small plants and breakage of lower stems on larger plants. It is unknown if this recently described insect species is native or introduced.

As you are checking soybean fields this season, pay close attention to any wilting plants on field edges. Peel back the epidermis at the base of the plant and look for small orange maggots.

Bob Koch and I would appreciate hearing about any infestations you discover. More on this insect later!

Seed corn maggot

If you are planting into fields where dry livestock or green manures have recently been worked in been worked, risk from seed corn maggot injury increases if planting occurs close to egg-laying by the flies. Anthony Hanson has placed degree-day models for this insect on the web at https://www.vegedge.umn.edu/scmdd. Slow crop emergence can increase seed corn maggot damage. There are multiple generations of this insect.

Two of the more unusual invertebrate pests to watch for in cool, wet, high residue conditions are slugs and millipedes. Damage from these pests is relatively rare in MN. Finding their damage is easy; managing these non-insect pests is not so easy. 

Soybean aphid

Should now be present on developing buckthorn leaves. It is unclear what effect the winter had on egg survival, particularly lower in the canopy. Additionally, last fall, for the first time since 2001, I was unable to find any soybean aphid on buckthorn at Lamberton and surrounding area.

However, as most have you have witnessed, the soybean aphid is capable of rapidly increasing its population on soybean. Where, and how well, the 2019 population becomes established will also depend on this spring’s weather and emerged soybean plants available when the aphids move from buckthorn.

Miscellaneous

Where it is dry enough to be possible, scout crop stands as they emerge.

Winter cereal crops that planted for grain harvest can use an initial scout for aphids and it would be worth starting to check alfalfa for insect issues also. We will be posting updates on what we find at Lamberton and elsewhere in future issues.

As always, I appreciate y’all keeping me posted on any pest issues you are seeing.

Happy trails, 

Bruce Potter