Assistance with 2019 European corn borer and corn disease survey requested

The following article was written by University of Minnesota Extension IPM specialist Bruce Potter, entomologist Bill Hutchison and plant pathologist Dean Malvick. Note that in the northwest I am still looking for fields in Clay, Clearwater, Kittson, Marshall, Norman, Pennington, Polk, Red Lake and Roseau Counties. 

Entomologists and plant pathologists at the University of Minnesota continue to document and understand changes in European corn borer (ECB) populations and corn diseases in our state.

Each fall, approximately 150 corn fields are surveyed for the presence of corn borer damage (Figure 1), overwintering corn borer larvae, and corn diseases. During the growing season, weekly updates of ECB moth captures in black light traps are made available at: https://www.vegedge.umn.edu/moth-data/ecb-info. Funding from the Minnesota Corn Research and Promotion Council has provided us an opportunity to improve these efforts.

Figure 1. Overwintering European corn borer larva in corn stalk.

Monitoring still important

Since the widespread adoption of Bt traits in the 1990s, populations of ECB been quite low; the areawide suppression of ECB has been correlated with Bt use rates. Over the past few years, corn growers have increased the number of acres planted to hybrids without Bt traits (conventional corn) for ECB. Additionally, Bt resistant ECB populations have recently been reported from Canada. Several corn diseases have been observed to be increasing or expanding their range in the state. These issues highlight the importance of maintaining annual monitoring efforts for this insect.

To ensure that insect and disease survey results reflect the effects of the non-Bt acres as well as the overall crop mix, we need to include a percentage (at least one field/county) of the conventional corn acres in survey efforts for each county. We will also collect overwintering stage larvae from fields where ECB populations are large. These larvae will be reared to determine the prevalence parasites and/or the single generation strain of this insect.

Can you help?

We are still looking for cooperating corn growers to help us improve the accuracy of survey efforts for corn insects and diseases and will be starting the survey soon.

If you would allow us to sample one of your conventional corn fields this fall, please contact Bruce Potter (bpotter@umn.edu) by September 16.

Please supply the following information:

• Your name
• Phone number or email
• Field location description of the field (GPS or County, Township, Section)

We will select surveyed fields to provide the best geographic representation of populations. Growers will be advised if we find their field has a high population of borers but individual field locations and farmer information will not otherwise be shared. Figure 2 shows previous ECB survey results.

Figure 2. Populations of ECB larvae (data interpolation) based on fall stalk dissections of field corn. The maps show the marked difference between recent populations (2016-18) and those before plantings of Bt corn were widespread (1995-97) when period outbreaks caused widespread economic yield loss.