Minnesota Crop News

by Robert Koch (Extension Entomologist)

While soybean aphid numbers have been generally low this year, defoliating insects (especially green cloverworm and thistle caterpillar) have been abundant in soybean fields across much of Minnesota. I have also received some scattered reports increasing defoliation from grasshoppers in northwest Minnesota and Japanese beetles in southeast Minnesota. To determine when to apply insecticides, rely on scouting and thresholds. Continue scouting through pod and seed development. Below is a summary of scouting and thresholds for defoliating insects from an earlier Crop News article. 

When needed, sulfur fertilization can produce profitable increases in corn yields. In this short video, Extension soil fertility specialist Dan Kaiser walks you through how to choose the right source of sulfur, and when and how to apply effectively.


For more information, read our sulfur guide.

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Support for this project was provided in part by the Agricultural Fertilizer Research & Education Council (AFREC).

by Robert Koch (Extension Entomologist) and Bruce Potter (Extension IPM Specialist)

Soybean aphid populations have been generally low across Minnesota. However, populations in some fields in southwest and southeast Minnesota are nearing threshold levels and may require insecticide application to protect yield. In these areas, soybean aphid infestation levels very considerably from field to field, so you should rely on scouting and the economic threshold (80% or more of the plants with aphids, average of 250 aphids per plant, aphid numbers increasing) to determine when to apply insecticides for soybean aphid.

As folks consider spraying fields for soybean aphid, we want to remind everyone that soybean aphid has developed resistance to pyrethroid (Group 3A) insecticides. Currently, any populations of soybean aphid in Minnesota should be considered potentially resistant to pyrethroids. Insecticide rotations are an important part of insecticide resistance management and may help reduce the…

by Hannah Rusch, Jeff Coulter, Julie Grossman, Gregg Johnson, Paul Porter, and Axel Garcia y Garcia

Balancing the supply and demand of nitrogen (N) in crop production is challenging. In most cases, application of N fertilizer is needed to ensure that adequate N is available to corn. Nitrogen that is not taken up by plants can be lost from cropping systems as nitrate through leaching or runoff.

Cover crops can help to manage nutrients within cropping systems. One function of cover crops is to capture available soil N by storing it in their tissues. The period between corn harvest and winter is limited by cool air temperatures and short days, making cover crop establishment following corn harvest a challenge. Interseeding cover crops into corn can increase the amount of growing degree days and solar radiation available for cover crop establishment and growth prior to winter. However, this strategy may raise concerns about competition of cover crops with corn.
Cover crop study To evalu…

by Robert Koch (Extension Entomologist) and Rafael Carlesso Aita (Graduate Student)

The brown marmorated stink bug (BMSB) has been detected in soybean fields in Dakota County, Minnesota for three years in a row. From 2016 to 2018, low numbers of BMSB adults and nymphs were collected in sweep net samples in those fields from mid-August to mid-September. During the pod and seed development stages, soybean is attractive to stink bugs and susceptible to their feeding injury. However, due to the low densities of BMSB observed in Minnesota the last few years, we don’t expect any substantial injury from this pest at this time. However, as populations of BMSB continue to spread and increase, it could become a pest that growers will need to actively manage, which is the situation in some of the eastern states. The purpose of this article is to inform you about the likely presence of low numbers of BMSB in soybean fields in southeast Minnesota. If you find any life stages of BMSB in your crops,…

By Lizabeth Stahl, Extension Educator in Crops

If you would like to hear the latest research and information on cover crops from University of MN researchers and educators, reserve your spot for the U of MN field day “Cover Crops: Setting up for Success”, August 20, at the Southwest Research and Outreach Center in Lamberton. University research will be highlighted when discussing management tips and considerations to help farmers and Ag professionals successfully incorporate cover crops into Minnesota cropping systems. Check-in will start at 8:30 and the program will run from 9:00 AM to 2:30 PM. 
Registration is requested by August 13 at https://z.umn.edu/cover-crops-success or by calling 507-752-7372 to help with the meal count. The first 40 paid registrants will receive a FREE copy of the “Midwest Cover Crops Field Guide” 2nd Edition. The $25 registration fee includes lunch, refreshments, and handouts.  Topics & speakers include: Cover Crop Demo. Key cover crops for Minnesot…