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10-Minute Paper

Plant-Insect Ecosystems

P-IE: IPM - Field Crops 1

Parsing the halo-effect for Bt crops: Spatio-temporal dynamics for 25 years of European corn borer areawide suppression in Minnesota and Wisconsin

Wednesday, November 8, 2023
9:36 AM – 9:48 AM ET
Location: Gaylord National Resort & Convention Center, Maryland 5-6
In-Person
Genetically engineered (GE) crops, Bt corn and Bt cotton, which express several Bacillus thuringiensis Cry toxins, have been widely adopted in the U.S. and more than 28 countries. Numerous studies have documented economic and environmental advantages of GE crops, including the benefits of insect pest suppression in nearby non-Bt crops, including high-value vegetable crops. This unique benefit of pest suppression has been characterized as the “Halo-Effect.” Despite early theoretical evidence for the halo, and empirical data for some pest species, little research has demonstrated how the halo can be measured. Moreover, a better understanding of the mechanisms of pest suppression in non-Bt or refuge crops is necessary to show how the halo can be used by growers (and industry) to optimize Bt crop deployment for long-term value. Expanding on a previous 60-year “fall survey” data set for two corn-belt states in the Midwest U.S., we examined temporal and spatial dynamics of pest population growth, before and after the advent of Bt corn. We used data from Minnesota to build an empirical model documenting the halo then validated the model using Wisconsin data. The current analysis indicates an optimal planting density of 40-50% non-Bt corn, over multiple years, will best maintain sub-economic corn borer populations. Accounting for the beneficial impacts of the halo-effect can inform decisions to better balance the trade-offs between maintaining long-term efficacy and mitigating the evolution of Bt resistance in pest species.