Effect of Larval Diet on the Seasonal Occurrence of Diapause in the Pink Bollworm1

Abstract

The pink bollworm, Pectinophora gossypiella (Saunders), was reared in an open in sectary and in the laboratory on three synthetic diets. Diets utilized were a 5% cottonseed meal diet, a 1% cottonseed meal diet and a wheat germ diet. The 5% meal diet had the highest oil content and the wheat germ diet the lowest. Cultures were placed in the in sectary and laboratory locations at weekly intervals from late June to early November. Results indicated that diet had little effect on the occurrence of diapauses until other inductive stimuli came into play. The highest incidence of diapauses then on the diets having the greatest oil contents. When the period between sunrise and sunset decreased to approximately 12 hours (mid-September) or less, the incidence of diapauses increased abruptly in both the in sectary and the laboratory. Temperature appeared to have an additive effect to the photoperiodic stimulus; however, temperature alone may be sufficient stimulus to induce diapause in the pink bollworm.