Studies on Cold Hardiness and Diapause Initiation of Agromyza frontella (Rondani) (Diptera: Agromyzidae)

Abstract

The supercooling-point values for field-collected and laboratory-reared alfalfa blotch leaf miner, Agromyza frontella , pupae were always below −;25°C with no evident seasonal changes, as reported for other northerly freeze-intolerant species. Nondiapausing pupae were exposed to −10°C for 21 days at different stages of pupal development and then returned to 20°C. Some adults emerged, particularly from pupae placed at −10°C at 6 and 9 days of age, a developmental stage similar to the partially developed overwintering individuals. Photoperiodic conditions during egg and larval development influenced the initiation of pupal diapause, which increased from 55% with a decrease in the light period from 18 to 10 h, at both 15 and 20°C. The effect of temperature was less pronounced, although under a 14 h light period significantly more pupae were in diapause if eggs and larvae were reared at 15°C (39.8%) than at 20°C (22.3%).