Yellow traps reloaded: what is the benefit for decision making in practice?

Abstract

Sticky traps are a standard tool for monitoring alate arthropod pests in greenhouses. However, in practice, evaluation of traps over the whole growing season is rarely done. For decision making by growers, sticky traps are often only used for detection of pest presence. The reason behind is that although many studies show that pest pop- ulation densities can be estimated using sticky traps under experimental conditions, validation under growing condi- tions and monitoring of beneficials are often lacking. In the current study, we evaluated whether trap densities recom- mended for practice are sufficient to estimate pest popu- lation densities of Trialeurodes vaporariorum (Hemiptera: Aleyrodidae) and its natural enemy Encarsia formosa (Hymenoptera: Aphelinidae) in protected tomato cultures throughout the growing season. Our results show that trap catches provide reliable information about pest densities, in which correlations differed for specific developmental stages, i.e. adults\nymphs\nymphs (previous week). A single yellow sticky trap provided reliable information on nymphal density in the tomato crop on an area of at least 170 m 2 . A rapid increase of parasitoid trap catches indi- cated high parasitism. In our experiments, a total trap catch of C6 parasitoids/trap was a suitable threshold for sufficient natural enemy activity in the tomato crop. The implementation of these results in practice and the trans- ferability to other cropping systems are discussed.