Description

As a part of the project “LichtFalle: Scaring, attracting, mapping and selectively kill harmful insects using a mobile LED laser combination trap” founded by BMEL, a pest control strategy should be developed, which aims to disturb pest insects on the plant and induce dispersal flights using a specific stimulus. Then they should be lured to a light trap and finally killed selectively by a laser application.
In a series of laboratory experiments under controlled conditions, the effects of blue and UV light on the behavior of natural enemies in ambient light (day conditions) and dark (night) conditions was investigated. Thereby, the behavioral reactions of the individuals on selective disturbing light, with and without a host being present, were analyzed. Studies showed that the whitefly Trialeurodes vaporariorum (Westwood, 1856) (Homoptera: Aleyrodidae) can be quantitatively disturbed by blue and UV LEDs (light emitting diodes) from a host plant. In this study, therefore, it was examined whether natural enemies of whiteflies, i.e., Macrolophus pygmaeus (Rambur) (Heteroptera: Miridae) and Encarsia formosa (Gahan) (Hymenoptera: Aphelinidae), can also be disturbed by these light colors and whether the result can potentially affect the biological plant protection. Additionally mechanical cues i.e., air puffs were used to determine their disturbing effect on M.pygmaeus. The results showed that M. pygmaeus and E. formosa are sensitive to blue light (465 nm) and UV light (370 nm). Both insect species walked away from blue and UV light in greater distances compared to the two control groups (no LED/white LED), when there was no host present. In dark, night- like conditions, this effect increased mainly by UV light. In presence of T. vaporariorum nymphs, M. pygmaeus showed a disturbing reaction under UV light, moving from the underside to the upper side of the leaf. In contrast, under blue light, M. pygmaeus showed no avoiding reaction within the 60 minutes observation time. The parasitoid wasp E.formosa did not show any avoiding behavior within the 60 minutes observation time under UV light. Under blue light E.formosa showed a tendency of avoiding behavior. A flying dispersal behavior could not be induced in the experiments in presence of a host, as the insects avoided the light by walking away. When using air puffs, most of the individuals (55% out of 20 individuals) flew away by the first air puff of 1 second.
In general, both insects reacted on the same disturbing light as the greenhouse
whitefly T.vaporariorum. In presence of a host they showed predominantly a local avoiding reaction from the illuminated leaf areas. Further investigations under natural conditions will show whether the observed reactions to the short wavelengths can also be shown in greenhouses and whether beneficial insects get disturbed by the light and lured to the light trap.