Management of corn earworm Helicoverpa zea in sweet corn grown for processing can be challenging due to the lack of effective transgenic and chemical control options. However, biological control by generalist predators can provide a significant impact on pests in this cropping system. One of the most ubiquitous predators of H. zea and other lepidopterans is the insidious flower bug, Orius insidiosus. This small hemipteran has been observed as an important mortality agent of H. zea in several cropping systems, but the strength of the trophic connection between these species has not been documented in sweet corn. Molecular gut-content analysis was conducted to test field-collected O. insidiosus for the presence of H. zea DNA using species-specific PCR primers developed and optimized for this project. Controlled feeding trials determined that the detectability half-life of this technique was 2.32 h. At peak predation in late August, 32% of O. insidiosus tested positive for H. zea DNA. The date of peak predation also corresponded with peak silking of sweet corn plants, which is the most attractive crop growth stage to both H. zea and O. insidiosus. These results indicate that within a short window prior to collection from the field, on the peak date of predation, approximately one third of O. insidiosus in sweet corn had consumed one to two H. zea eggs and/or first instar larvae. The demonstration of this high frequency of predation allows for the assertion that O. insidiosus is a critical mortality agent of H. zea in sweet corn, and conservation biological control practices should be explored to protect and promote this key predator.
Bibliographical noteFunding Information:
We would like to acknowledge Kacie Athey and Eric Chapman (Department of Entomology, University of Kentucky ) and Laurel Mosca and Paige Owens-Kurtz (Department of Entomology, University of Minnesota ) for their assistance with technical aspects of the project and Stephen Kachman (Department of Statistics, University of Nebraska-Lincoln ) for his assistance with data analysis. This research was also supported by the Minnesota Agricultural Experiment Station ( MAES ), University of Minnesota, St. Paul.
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- Biological control
- Corn earworm
- Gut-content analysis
- Insidious flower bug
- Predator-prey interactions