Large scale testing of sticky traps for monitoring spittlebugs in different crops

Monitoring spittlebugs has become crucial for the implementation of preventive measures against the spread of Xylella fastidiosa in Europe. So far, sweep nets have been commonly used to monitor spittlebugs in ground vegetation and canopies of trees or shrubs. From 2018 to 2020, we conducted several field experiments to test the effectiveness of sticky traps as tool for monitoring insect populations in different crops.  We evaluated different coloured sticky traps (white, red, blue, yellow, yellow with circle-pattern and yellow with line-pattern) in comparison with sweep nets, and validated their efficiency on olive, almond, and cherry orchards. Results showed that: (i) yellow traps were the most attractive for Philaenus spumarius and Neophilaenus campestris; (ii) while in olive groves no differences were recorded for the yellow traps with different background, in the almond and cherry orchards, the capture of P. spumarius on those with black line-pattern were significantly higher than the other in some of the inspection periods; (iii) leafhoppers were the predominant non-target insects captured on the yellow sticky traps in our experimental fields. Comparison between yellow sticky traps and sweep nets for monitoring P. spumarius clearly showed that early in the season (April-May), i.e. when the adults emerge, insects were prevalently caught by sweeping net. Later on, the number of adults captured on traps were constantly higher than those captured by sweep nets, especially in olive groves with medium-high population densities and in almond and cherry orchards. In conditions with low population densities of P. spumarius, the two methods showed similar efficiency. Regarding N. campestris, no differences were observed between the two sampling methods on olive trees and cherry. While on almond yellow sticky traps were mostly effective than sweep net, prevalently in late summer when leaves fall and sweep net were difficult to use due to the stiffness of the branches. Our results suggest that the use of sweep nets soon after the emergence of the adults coupled with sticky traps for the rest of the adult season, can expedite monitoring programs finalized to the implementation of control measures (i.e. defining the threshold and the best time for insecticide applications).