As the first warm days arrive in spring, founder queens of Vespa velutina emerge from hibernation and starts flying and looking for an optimal nesting site. In this season, the hornets are particularly attracted by nectar and other sugars’ sources. The period between March and May is thus the best time to effectively monitor Vespa velutina. This activity aims mainly to detect the presence/absence of the hornet and discover new invaded areas. The monitoring can be performed using specific traps for hornets, which should be hung in and around apiaries or in other areas, such as gardens, parks, etc.
The traps may be constructed using simple transparent PVC bottles with a capacity of 1.5 l , filled with 33 cl of common lager beer (4.7%) as attractive. The alcohol inside the beer will avoid that other pollinators, like bees, may be captured by the trap. Each bottle may be equipped with a cap well suited for this use, easily available in commerce. The cap will keep the rainwater out from the trap and will facilitate the replacement of the bait. A further possibility may be the use of a self-made device: in this case, the trap should be equipped with a cover to ensure an effective drainage of rainwater. The trap has to be checked once every two weeks, and, by the occasion, the attractive bait has to be replaced with a fresh one.
The monitoring activity to detect Vespa velutina has to be done firstly by the beekeepers, but each citizen may also contribute for a more widespread monitoring of the environment. The areas chosen for the trap and the presence of suspect hornets may be communicated to the competent authorities; in Italy, reports could be sent to the LIFE STOPVESPA project (firstname.lastname@example.org - +39 335 6673358). Even if the result of the monitoring is negative for Vespa velutina, it is in any cases important to communicate it at the end of the activity, in early summer.
We would like to thanks all people that are already contributing to the monitoring activity of Vespa velutina and those who will contribute in the future, and helping us to contain the spread of this invasive hornet species predator of honeybees.