Rice leaffolder,Cnaphalocrocis medinalis(Guenée),has become a major pest throughout the rice cultivating areas of China and caused severe damage to rice production.Cnaphalocrocis medinalis granulovirus(CnmeGV),a naturally occurring baculovirus,is revealed as a potential microbial agent for the pest control.Field applications of CnmeGV were conducted against rice leaffolder larvae in rice paddies.CnmeGV infected the larvae not only in the current generation but also in the successive generation,resulting in a sustained infection in the larva population for at least 48 days.Under diferent concentrations of CnmeGV(7.5×1011 and 1.125×1012 occlusion body(OB)ha-1)at 30 days after spraying,larval population reduced up to 76.32%and rice leaf rolled rate kept in 15.42%.Simultaneously,CnmeGV had no impact on arthropod predators of C.medinalis,with abundances ranging from 2.39 to 3.79 per ten hills.These results revealed that CnmeGV is suitable as a bio-pesticide for rice leaffolder management in rice paddies.
The growth and reproduction of rice leaffolder,Cnaphalocrocis medinalis,fed on an artificial diet were studied.The results showed that the larvae were able to grow and pupate on the artificial diet.The durations of larvae and pupas of C.medinalis on the artificial diet were 28.1 d and 10.1 d,postponed 4.9 d and 1.7 d respectively,compared with those reared with rice leaves.The number of ovipositions was 41.6 per female,26.2% higher than that fed on rice leaves.Survival rate curve of larvae was a descent function of mortality-age,with no significant differences from the curve of larvae fed on rice leaves.The net reproductive rate (Ro),intrinsic rate of increase (rm) and finite rate of increase (λ) of the population fed on diet were 17.6928,0.0884 and 1.0924,respectively,and the mean generation time (T) and double time (td) were prolonged 4.9 d and 1.3 d in comparison with the treatment of rice leaves.Population trend index (I) was 3.26,indicating a growing number of the population of C.medinalis fed on artificial diet.
