Light-emitting diode traps in commercial greenhouses: A field study report on Encarsia formosa bycatch

Yellow sticky traps (YSTs) are a standard tool for insect monitoring in greenhouses. These traps have been further developed by using them in combination with green light-emitting diodes (LEDs) to increase their attractiveness towards pest insects such as aphids and whiteflies. However, also natural enemies, such as the whitefly parasitoid Encarsia formosa Gahan (Hymenoptera: Aphelinidae), are attracted to these traps. This may cause problems with biological control of the pest or may be used for indirect monitoring purposes. Therefore, we compared the attractiveness of YSTs and green (521 nm) LED traps towards E. formosa under practical growing conditions in tomato, Solanum lycopersicum L. (Solanaceae) and cucumber, Cucumis sativus L. (Cucurbitaceae), crops in the greenhouse. The aim of the study was to investigate the compatibility of LED traps with this parasitoid frequently used against the greenhouse whitefly, Trialeurodes vaporariorum Westwood (Hemiptera: Aleyrodidae). The results show LED traps catching less E. formosa than standard YSTs. Moreover, LED traps also showed compatibility with other beneficial insects. The results are discussed in the context of the parasitoid's behaviour towards various green light spectra and in the context of pest and beneficial insect monitoring using different trap types. Our study will help implementing green LED traps in future insect monitoring programmes and developing new pest control strategies without affecting natural enemies.