Development of a System To Time Scouting for the Lesser Cornstalk Borer (Lepidoptera: Pyralidae) Attacking Peanuts in the Southeastern United States

Abstract

We developed a system to time scouting for the lesser cornstalk borer, Elasmopalpus lignosellus (Zeller), in conventionally planted and tilled fields of peanut, Arachis hypogaea (L.). The system used borer-days (BD) to predict when to scout for the damaging larval stage. Borer-days was patterned after degree-days and is a running total of hot and dry weather minus cooler and wetter weather during the growing season. Number of borer-days explained 67% of the variance in the density of E. lignosellus larvae during the 1986 population outbreak in Alabama and Georgia. We calculated the number of borer-days for the past 9 yr and found that borer-days reached >10 in the outbreak years of 1980, 1986, and 1990 but never reached this value in years when E. ligllosellus did not achieve outbreak densities. Applying a granular insecticide at 0 to + 10 BD increased yield compared with yield in untreated plots. Yields did not increase when a granular insecticide was applied at <;0 BD. Borer-days can be a valuable tool in predicting when to scout for this insect.