Effects of the Insect Growth Regulator Hydroprene on Diapausing Alfalfa Weevils 123

Abstract

Hydroprene, when topically applied, terminated sexual diapause of adult Hypera postica (Gyllenhal). Significant changes in gonadal development, oviposition, and feeding were related to the concentration applied. A 1-μg amount of hydroprene terminated diapause in 15% of weevils, did not influence testis size, produced small increases in ovary size, instigated atypical oviposition in 10% of females, and increased feeding for 27 days. A five-μg amount terminated diapause in 37% of weevils, produced moderate increases in testis and ovary size, instigated atypical oviposition in 20% of females, and increased feeding for 27 days. A 10-μg amount terminated diapause in 66% of weevils, produced large increases in testis and ovary size, instigated atypical oviposition in 60% of females, and increased feeding for 37 days. A 50-μg amount terminated diapause in 100% weevils, produced large increases in testis and ovary size, instigated typical oviposition in 90% of females but with reduced egg fertility, and increased feeding for 49 days.