Use of yellow sticky traps to study daily flight activity and behaviour of sap-sucking insects inhabiting European vineyards

Yellow sticky traps are used to monitor sap-sucking insects in their roles as both pests and vectors across a broad range of crops including vineyards. They are also used to understand different aspects of insect biology, and for this purpose, a number of studies have been conducted to determine the daily flight activity of leafhoppers and thrips. In a vineyard in north-eastern Italy, the daily flight activities of leafhoppers [e.g. Empoasca vitis (Gothe), Zygina rhamni Ferrari, Scaphoideus titanus Ball], as well as the vine thrips Drepanothrips reuteri Uzel, were studied with yellow sticky traps during different monitoring days of the growing season. The traps were placed in both shady and sunny positions with respect to the grapevine foliage, and in inter-rows. They were routinely replaced every hour from the start of dawn to the end of dusk, while during the hours of darkness there was no replacement, except on one monitoring day. E. vitis, S. titanus and D. reuteri were mainly captured in sunny positions, while Z. rhamni was captured in shady positions. E. vitis exhibits bimodal daily flight activity with two peaks respectively at the dawn-sunrise and sunset-dusk. Z. rhamni prefers to fly around sunrise, when daily temperatures are lower, and S. titanus flies continuously from sunset to sunrise. The vine thrips flies only during sunshine hours. The daily hours with higher flight activity are mostly associated with changes in light intensity. The moderate light intensity that occurs immediately after sunrise and just before sunset inhibits the flight activity of leafhoppers outside the canopy but not inside. Knowing the daily flying activity and behaviour of leafhoppers and thrips can have important implications for establishing the optimal sampling time because in the hours of the highest flying activity counting adults can be more difficult.