Yellow sticky traps for decision-making in whitefly management: What has been achieved?

Yellow sticky traps (YSTs) are a key component of IPM programmes for several greenhouse pests. The development of YST-based decision-making tools, e.g. sampling protocols and economic thresholds (ETs), however, has been limited. This review assesses to what extent YST-counts comply with the four criteria of effective sampling (reliability, representativeness, relevance and practicality) as described by Binns et al. (2000) in an attempt to understand the feasibility of designing YST-based decision-making tools for managing whiteflies in greenhouse crops, particularly tomato (Lycopersicon esculentum Mill) and cucumber (Cucumis sativus L.). Many factors are known to affect whitefly flight behaviour and thus, trap catches. The possibility of manipulating such factors to improve YST efficiency and reliability or of interpreting whitefly catches in YSTs with automated tools is discussed. A few studies have shown the correlation between trap and direct visual pest counts from plants. These studies are discussed in the context of whiteflies and trap densities to enhance the representativeness of sampling with YSTs. Relevance implies that the results of sampling reflect crop loss to a sufficient degree. Only few YSTs-based action thresholds have been suggested in the literature, particularly for use with chemical control. There are a number of approaches and technological innovations that can improve the practicality of YSTs by decreasing the effort and time associated with counting insects, a method to facilitate the identification of species in mixed populations on the trap, and sampling methods such as sequential sampling for calculating appropriate sample size, which have been already put in practice to develop YSTs-based sampling protocols. Knowledge gaps are identified and discussed, and a route map for further research to advance YSTs as a decision-making tool is outlined, with geostatistical methods as the recommended approach for further increasing the usefulness of YSTs-based decision-making.