Leafminers (Liriomyza sp.) importance in greenhouses in the Oeste region of Portugal and its natural parasitoids as control agents in IPM programs
2000
Godinho, M. ((Escola Superior Agraria de Viseu (Portugal))) | Mexia, A.
Leafminers species were considered as a key-pest on vegetable greenhouses in Portugal, particularly in the Oeste region of Portugal. Liriomyza trifolii (Burgess) and Liriomyza huidobrensis (Blanchard) are the two species, which were accidentally introduced before 1986 and 1990 respectively. The studies that were developed during five years are related with: (1) identification of the leafminer species, (2) identification of the parasitoids complex species, (3) population dynamics in different agroecosystems, (4) monitoring, (5) evaluation of the parasitoids role as natural control agents, (6) and the development of an IPM program against leafminers in greenhouse vegetable crops. The importance of the leafminers damages in the different crops, the leafminers species present and its parasitoids complex species are presented and discussed. Since 1991, L. huidobrensis dominates the leafminers species complex in greenhouse vegetable crops in all of the three " different " greenhouse agroecosystems that were surveyed. Yield losses occurred more frequently in green beans and lettuce crops. The damages on curcubits and tomato seemed as being tolerable in general. The complex of the parasitoid species is very dynamic. In fact, the abundance and parasitism rates found varied during this period. In 1993 levels of parasitism of 100 percent were observed with Diglyphus isaea Walker + Diglyphus poppoea (Walker) and during 1994-95 the two most important species were D. isaea + Diglyphus crassinervis Erdos. The presence of Dacnusa sibirica Telenga was also registered as well as other species with less abundance. Natural control is frequently enough to maintain populations on tolerable levels that is based on the activity of autochthonous fauna
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