Natural enemies for tomato pest control in Sardinian greenhouses

Supported by public funds during the 1990s, integrated control measures, like beneficials augmentation, were implemented in more than one-third of Sardinian tomato greenhouses. In recent years, the situation has changed considerably, and the release of natural enemies has been greatly reduced. Nevertheless, the most competitive tomato growers, who export their high quality produce to the more remunerative markets outside the island, still consider the use of biocontrol agents an interesting option. In order to evaluate current results of pest management and compare the effectiveness of biological and chemical control measures in commercial tomato greenhouses, a survey was carried out during cropping season of 2003/2004. 7 long-cycle and 10 short-cycle tomato crops (6 fall and 4 spring crops), located in one of the major horticultural district of the island (Pula, Cagliari), were monitored. Population trends of whiteflies (Bemisia tabaci and Trialeurodes vaporariorum) and lealminers (Liriomyza spp.) were assessed in crops where pest management practices included seasonal inoculative releases of Macrolophus caliginosus, Encarsia formosa and Diglyphus isaea or relied on insecticide treatments. For most of the cropping period, predation and parasitism exerted by the released beneficials did not seem to influence significantly the development of whiteflies populations. While leafminer infestations were adequately controlled by insecticide treatments or D. isaea releases on fall and long-cycle crops, Liriomyza management was more difficult on spring crops. The results of this survey suggest that, under common cultural conditions, the potential of natural enemies might not be expressed fully: adjustments of biological control practices implemented in Sardinian tomato greenhouses could be necessary.