Diamond-back moth 40 years hence: is it still a menace to cruciferous crops?
2005
Colting, L.M. | Morallo-Rejesus, B. | Versola, E.A. | Mangili, T.K. | Cardona, E.V. | Alimurong, T.A., Benguet State Univ., Trinidad, Benguet (Philipines); Philippines Univ. Los Banos, College, Laguna (Philippines). Crop Protection Cluster; Department of Agriculture, Cordillera Autonomous Region (Philippines); Bureau of Plant Industry, Baguio City (Philippines)
Diamondback moth (DBM), Plutella xyllostella (Linn.), has been a major pest of crucifers in the Philippines since mid 60's while Pieris canidia canidia (= rapae) Sparrman became minor pest. Complete reliance for more 20 years on insecticides to control DBM resulted in the development of DBM strains with multiple or cross-resistance. Farmers then mixed 2 to 3 kinds of insecticides, increased the frequency of application and even used cyanide (early 1990's) that almost destroyed the vegetable industry in the Cordillera. An interagency IPM-DBM Task Force was created and the IPM concept introduced through the Farmers Field School (FFS). The season-long (planting to harvesting) training focused on biological control, cultural management practice, and conduct of an ecosystem analysis to convince farmers that pests can be reduced through a need-based use of pesticide less toxic to natural enemies. In 1989, larval parasitoids Diedegma semiclausum Hellen and Cotesia plutellae (Kurdji) in southern and northern Luzon effectively reduced DBM damage. Survey in 1996 in Cordillera showed reduction in number of insecticides sprayings from 32 to 8 times per cropping season and lengthened application interval from 5 to 20 days, thus reducing insecticide sale in Benguet and Mt. Province to 58.65 percent of that in 1991, and that above 75 percent of the farmers were using Diadegma. Cotesia releases reduced the number of spray applications to 1-6 times from 21-30 times before parasitoid release, greatly reducing production cost and increasing cabbage yield. Both Diadegma and Cotesia have been established in Cordillera and Southern Tagalog, respectively, with parasitization ranging from 32 to 80 percent in the farmer and 74 to 92.5 percent in the latter. With DBM population reduced there is now apparent re-emergence of cabbage butterfly P. canidia canidia in Cordillera and Crocidolomia pavonana (=binotalis) (F) in warmer areas of Luzon, both destructive pests of crucifers in the 50's to 60's in said areas.
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