Minnesota Corn: Skip Bt Traits? Weigh European Corn Borer Options

European corn borer larva and damage. Photo: Bruce Potter

The economics of 2018 corn production challenge many farmers with minimizing losses per acre. One area some farmers have targeted for reducing costs is hybrid selection. Planting corn hybrids without Bacillus thuringiensis (Bt) proteins for protection against European corn borer (ECB), corn rootworm or both will greatly reduce seed costs.

However, if not careful, farmers could inadvertently reduce crop revenues if they select hybrids without considering yield potential or insect populations in their fields.

Yield potential is the first thing to consider when selecting a corn hybrid. Bt traits only protect the yield potential of a hybrid; yield benefits only occur when targeted insects are above economic levels. When insect pressure is low or absent, economic benefit with trait-protected hybrids only occurs if higher costs are offset by greater yields. Switching to less-expensive non-Bt seed can be a good strategy when yields are comparable or when seed cost savings exceed any reduced yield potential plus prospective insect losses. In many 2018 fields, planting corn without a Bt trait can work, if you recognize your insect risk.

Historical, current and future ECB populations

Since the adoption of Bt corn 22 years ago, Bt use rates in Minnesota have grown to approximately 80% of the total acres planted, including the 2017 season (Figure 1). ECB populations throughout most of the Midwest Corn Belt have been effectively suppressed by a similar adoption of Bt. ECB populations continue to be low in Minnesota where Bt use has remained relatively high since 2007. Low ECB moth flights (Figure 2) parallel the low ECB larval populations detected in…

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