Effects of temperature and winter diapause on survival and development in bivoltine and trivoltine ecotypes of the rice stem maggot, Chlorops oryzae Matsumura (Diptera : Chloropidae), reared on a winter host

Abstract

In Chlorops oryzae, winter diapause in the first larval stage is induced by short days in the egg stage and maintained by short days in the larval stage. On wheat plants (winter host), most diapause and non-diapause larvae failed to pupate and died within 50 days at 23°C regardless of photoperiod. When diapause larvae were reared on wheat plants at 10, 15 or 20°C under LD12 : 12, the survival rates increased with decreasing temperatures. Diapause development at 10°C was completed about 70-90 and 40-50 days in the Akita (bivoltine, 39°N) and Aichi (trivoltine, 35°N) strains, respectively. The survival rates on wheat seedlings at 23°C in diapausing larvae of the Akita strain increased with increasing periods of previous exposure to 10°C from 41 to 80 days. Aichi larvae showed higher survival rates regardless of the period at 10°C. It appears that low temperature promotes survival of the larvae on wheat plants, and larvae which complete diapause development can grow to the pupal stage on winter hosts.