Second‐Brood Southwestern Corn Borer Infestation Levels and Their Effect on Corn1

Abstract

AbstractThe southwestern corn borer, Diatraea grandiosella (Dyar), is recognized as a serious pest of corn, Zea mays L.; however, no data relating level of second‐brood southwestern corn borer infestation of corn and the resulting damage have been reported. To determine the effects of varying levels of second‐brood southwestern corn borer infestation, corn plants were infested at anthesis with 0 to 35 southwestern corn borer eggs in a field study grown at Mississippi State, Miss, on a Leeper silty clay loam (fine, montmorillonitic, nonacid, thermic, Vertic Haplaquepts) in 1974, 1976, and 1977. Grain yields were measured and stalks were dissected after harvest to determine the extent of tunneling. Infestations with increasing numbers of southwestern corn borer eggs were accompanied by a linear decline in yield. A quadratic type curve best described the relationship between number of eggs and number of tunnels in a plant and between number of eggs and extent of stalk tunneling. Damage sustained by corn plants infested with 25 to 35 eggs was heavy and differences among treatments were slight. These results indicate that investigators involved in the evaluation of corn genotypes for southwestern corn borer damage should consider applying approximately 30 eggs per plant in order to achieve a uniform, heavy infestation.