Aphids are important pests in many greenhouse and field crops. For plant protection, early detection of relevant species and reliable assessment of population development throughout the season is mandatory to address countermeasures in time. In practice, coloured sticky cards or pan traps are frequently used as monitoring tools, but as well as the flight activity of focal insects, many other factors influence reliable interpretation of trapping data. Since monitoring data have been more and more integrated into automated decision support systems, soundness of insect count data and interpretation of results needs to be reviewed in more detail. Therefore, we investigated the applicability of yellow sticky traps for monitoring of the cotton aphid, Aphis gossypii in greenhouse cucumber crop. In separate greenhouse chambers, we infested cucumber plants with Aphis gossypii and installed several yellow sticky traps. Insects were counted on the plants and sticky traps on a weekly basis and number of insects were correlated. Our results indicate mismatches between trap catches and aphid population density especially early in the season, which most likely is related to immigration of winged aphids into the greenhouse. The following population build-up of the cotton aphid Aphis gossypii on the cucumber plants correlated quite well with counts of alate cotton aphids on the sticky traps. In conclusion, trapping of winged aphids provides valuable information for integrated pest control in the greenhouse. Nevertheless, to avoid wrong interpretation the taxonomic identity of trapped aphids has to be confirmed at all times. Results are further discussed in the context of factors influencing aphid wing development and attraction to yellow sticky traps. Potential strategies to optimize aphid monitoring with coloured sticky traps are proposed.
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