Optimisation of monitoring procedures in plant protection through the targeted use of LEDs and semiochemicals

Insect monitoring is one of the key components of integrated pest management. Although yellow and blue sticky traps have been used to monitor aphids, whiteflies, thrips or natural enemies for decades, new monitoring tools, that could make monitoring more accurate and efficient, are rare. However, investigations with recently developed light-emitting-diode (LED) traps on pest insects have shown promising results to replace common sticky traps. Nevertheless, investigations on observing the population development of pest insects and natural enemies using these new monitoring approaches under greenhouse conditions are missing. However, new monitoring tools could contribute to a more sustainable plant production. Therefore, the approach of assessing the population development of Frankliniella occidentalis and Trialeurodes vaporariorum in the crop using common sticky traps and new LED traps was investigated. Moreover, LED traps were tested in practice investigating possible negative effects on the natural enemy Encarsia formosa. Comparing common blue sticky traps and blue (465 nm) LED traps with and without adding the semiochemical Lurem-TR® to these traps showed a significant increase of thrips catches on LED traps. Moreover, LED traps provided more accurate information on thrips density in the crop than the standard trap. Additional experiments showed that LED traps were not more attractive than host plants. Lurem-TR® only moderately enhanced the performance of both trap types in a greenhouse experiment but not under more simple conditions with low distances. This demonstrates the importance of visual cues for thrips to orientate at these distances. Comparing common yellow sticky traps and green (521 nm) LED traps in the greenhouse showed a significant correlation between the whitefly density in the crop and number of whiteflies caught on LED traps. As yellow sticky traps showed no such correlation, results indicate that green LED traps can be used effectively for observing the development of the whitefly population in greenhouses. To investigate the compatibility of this LED trap with the whitefly´s natural enemy E. formosa, LED and common yellow sticky traps were installed in commercial greenhouses. The results showed that the LED traps are not more attractive towards the parasitoid than the standard yellow sticky traps. Furthermore, results indicated the compatibility with other beneficial insects, meaning that their populations are not affected by using LED traps. In summary, this study showed the potential and suitability of utilizing LED traps as a monitoring tool. It also serves as basis for further improving insect monitoring and integrated pest management in greenhouses.