SW MN IPM Stuff 2019 Issue 7B

Volume 22 number 7b


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

This issue is available in a print-friendly pdf format: PDF iconIPM Stuff_2019-07b

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. In this part of the world, it’s been raining… a lot. Soybean weed control is going to be challenging again.

soybean gall midge larvaeFigure 1. An early instar soybean gall midge larva and damage to a V3 soybean stem.

Soybean gall midge 

I am hoping to pull together a field day for scouting and ID for next week. Will need to work through the issue of limited parking at the study sites first. 

In the meantime, here are a few more pictures of larvae from this year. 

The white early-instar larvae (Figure 1) are very small and easy to miss when examining plants. Beneath the stem epidermis, however, the damage to the lower stem of soybean can be impressive.

soybean gall midge larvaeFigure 2. As gall midge larvae mature, their color becomes orange. While refrigerated over the past weekend, this individual was able to continue its development. Mature larvae can be a bright orange color.

Late instar larvae are orange and much easier to see (Figure 2).

Damaging populations of this insect appear to be limited in Minnesota. Hopefully they can stay that way. 

When viewed under microscope lights, soybean gall midge larvae are quite active and we were able to film a group of them doing the soybean gall midge boogie. I am not holding my breath waiting for a best picture nomination from the Academy.

If you notice these insects and their damage, please contact me.

False Japanese beetle 

false Japanese beetleFigure 3. False Japanese beetle on a white petunia blossom. The beetles are often attracted to white flowers or other objects.

Over the past few days there has been some questions on medium sized (< ½ inch long) beetles that have been active, especially in areas with sandy soils in southern MN.  These are false Japanese beetles (Figure 3).  

They resemble small June beetles and are sometimes they are confused with the invasive Popillia japonica, or Japanese beetle, that has been plaguing the eastern Corn Belt including parts of eastern Minnesota. Being members of the Scarab family in beetles, both species share a June beetle body and antenna shape. The larvae of both feed on the roots of grasses and both have a single generation per year. The native, false Japanese beetle, Strigoderma arboricola, is much less metallic in coloration and lacks the Japanese beetle’s tufts of white hair along the abdomen (Figure 4).

Japanese beetleFigure 4. Japanese beetle on soybean

Large numbers of these beetles can be annoying when buzzing around corn and soybean fields, but they are not known to be crop pests. They can cause cosmetic damage to flowering ornamental plants, especially white or light colored. In addition to flowers, they seem to be attracted to white objects in general including clothing and pickups. 

Japanese beetle adults should be appearing soon. I would like to hear about any real Japanese beetles you might see in Minnesota west of Highway 169. 

Have a great 4th of July and...

Happy trails, 

Bruce Potter