Biological control of the American serpentine leafminer, Liriomyza trifolii (Burgess), on tomato in greenhouses by parasitoids. II. Evaluation of biological control by Diglyphus isaea (Walker) and Dacnusa siberica Telenga incommercial greenhouses.

The effectiveness of biological control against Liriomyza trifolii (Burgess ) on tomatoes was evaluated in commercial greenhouses. Five experiments wer e conducted at 2 locations, Hamaoka and Shimizu in Shizuoka Prefecture, fro m summer to winter in 1994, 1995 and 1996. Diglyphus isaea (Walker) and Dac nusa sibirica Telenga were released 3 to 9 times weekly after planting at r elease rates of 178 to 500 wasps per 10 a in biologically controlled greenh ouses. Only selective insecticides such as IGR and BT were applied in bio-c ontrolled (BC) greenhouses, whereas various insecticides including cion-sel ective pesticides were applied in chemical controlled (CC) greenhouses. In Hamaoka, the density of Leafminer larvae in BC greenhouses was kept at the same level as in CC greenhouses, and the mortality of leafminer larvae incr eased up to 100%. The density of mines and the number of adults captured by yellow sticky traps were kept at the same as or lower than those in CC gre enhouse, respectively. In Shimizu, the densities of leafminer larvae and mi nes, and the number of adults captured by yellow sticky traps in BC greenho uses were higher than those in CC greenhouses, but the mortality of leafmin er larvae increased up to 100% and the damage to tomato plants was not seve re. Maximum percentage of parasitism by the parasitoid complex based on the numbers of adult parasitoids that emerged from collected tomato leaves in BC greenhouses in Hamaoka and Shimizu were 100%. Dominant parasitoid specie s emerging from L. trifolii larvae in Hamaoka were D. isaea and D. sibirica , while dominant parasitoids in Shimizu were indigenous species. among whic h Neochrysocharis formosa and Hemiptarsenus varicornis were most dominant. Total frequency of insecticide applications in BC greenhouses were the same as or lower than those in CC greenhouses, but the frequency of insecticide application against leafminers was by far lower than those in CC greenhous es. These results suggest that biological control by the parasitoids agains t L. trifolii was practically effective on tomatoes in commercial greenhous es.