Life-table study of Anagrus atomus, an egg parasitoid of the green leafhopper Empoasca decipiens, at four different temperatures

The objective of our study was to assess the potential of the egg parasitoid Anagrus atomus L. (Hymenoptera: Mymaridae) for control of the greenhouse leafhopper Empoasca decipiens Paoli (Homoptera: Cicadellidae). The egg-adult development time, survivorship and reproduction of A. atomus were evaluated at four constant temperatures (16, 20, 24 and 28degreesC). Developmental time ranged from 33.6 days at 16degreesC to 13.3 days at 28degreesC. Based on a linear regression of development rate on temperature the lower threshold was estimated at 8.39degreesC. Anagrus atomus required 263.2 degree-days to complete its development from egg to adult. The egg-adult survival rate and the sex ratio were significantly lower at 28degreesC than at the other three temperatures tested. The intrinsic rate of increase (r(m)) varied significantly between all four temperatures. The potential of A. atomus to attack different host ages was additionally investigated. Host eggs were parasitized throughout their development but rate of parasitism was reduced in host eggs older than six days. The number of eggs parasitized was positively density dependent but the rate of parasitism decreased with increasing host density. A maximum rate of parasitism of 62.5% was recorded. The potential impact of the egg parasitoid on the population dynamics of E. decipiens is discussed.