Effectiveness and Selectiveness of Traps and Baits for Catching the Invasive Hornet Vespa velutina

SIMPLE SUMMARY: The introduction of invasive species is one of the major causes of biodiversity loss and, in many cases, entails considerable economic consequences. Due to their biological traits, social Vespidae are known for their potential in establishing viable populations and become invasive in many countries of the world. A good example is represented by the invasion success of the Asian yellow-legged hornet Vespa velutina, a species that has been introduced and established in Europe and other countries of Asia. By preying on honey bees and native insects, this species is a threat for the biodiversity, the pollination ecosystem service and the economy. Traps for wasps and hornets are widely used for monitoring the presence of V. velutina or, at a rather higher density, as a complementary method for limiting its impacts. Here we compared the performance of two typologies of traps and baits widely used for trapping this invasive species and, at the same time, evaluated the consequences of this activity on native insects. Findings highlighted that the performance of the trap/bite combinations changed in relation to the season. However, the proportion of non-target insects in the traps stress the necessity of developing alternative monitoring and control techniques. ABSTRACT: Vespa velutina is an invasive hornet that is colonising several countries worldwide, with detrimental effects on multiple components but primarily affecting honey bees and native insect species. Traps for wasps and hornets are commonly used for trapping V. velutina, both for monitoring and control purposes. In this study, we compared the performances of two typologies of traps and baits widely used for trapping this invasive hornet, by evaluating their effectiveness and selectiveness in trapping V. velutina in two sites during two different periods of the year, spring and autumn. The performance of the traps changed in relation to (i) the trap’s model, (ii) the bait’s typology and (iii) the period of the year. In spring, traps with common beer as bait were more effective and more selective independently of trap’s model than the commercial bait that has been tested. On the contrary, in autumn, just one combination of trap and attractant (the commercial trap and bait) achieved higher effectiveness and selectiveness. Despite the underlined variations among traps and baits, overall catches of V. velutina were scanty compared to bycatches of non-target insects, since best performing traps either in term of effectiveness and selectiveness caught 3.65% of the target species in spring and 1.35% in autumn upon the total trapped insects. This highlights the urgent necessity of developing more selective trapping methods for monitoring and particularly for controlling purposes.