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Midsouth Entomologist

Abstract

The corn borer complex, consisting of Diatraea grandiosella (Dyar), Ostrinia nubilalis (Hübner), and D. saccharalis (F.), poses a risk to field corn that is not protected through the use of foliar-applied insecticides or Bacillus thuringiensis (Bt) proteins incorporated into the plant's genetics. In the southern U.S., corn borers have been adequately controlled through the widespread planting of Bt corn hybrids. Refuge systems have been implemented to prevent the selection of Bt-resistant populations in target species. Historically, structured refuge compliance among corn producers has been low, leading to the commercialization of seed blended refugia in areas of the U.S. where cotton is not grown. It could be assumed that if seed blended refugia were approved for use in corn in the southern U.S., producers would not manage corn borers leading to the possible loss of refuge plants. To determine how a complete loss of refuge plants would affect yield, insect-related plant population loss was simulated at various levels ranging from 0% to 50% in 10% increments. Plant population loss was simulated at both the V5 and V10 growth stages. In low yielding environments, every one percent loss in plant population resulted in a 26.6 Kg Ha -1 reduction in corn yield. Subsequently, in high yielding environments, every one percent loss in plant population resulted in a 78.86 Kg Ha -1 reduction in corn yield. Results suggest that in a situation where a seed blended refuge was implemented into the mid-southern U.S., significant yield losses could be observed if refuge plants are left unprotected in the presence of high corn borer populations.

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