How to face swarming of pestiferous chironomids (Diptera) at Lake Trasimeno

In recent years, Lake Trasimeno has been affected by massive chironomid swarms, particularly in 2003. Waterfront resident and touristic activities markedly suffered from this annoyance. Therefore, since 2004, Local Administrations have promoted diversified actions in order to withstand the explosion of these insects with an attempt not to damage the ecosystem: 1) Larval control: treatment with Bacillus thuringiensis var. israelensis; this choice is justified by the low toxicological impact compared to commonly used insecticides. The bacterial activity takes place 12-18 hours after treatment and lasts for some days. 2) Adult control: i) use of insecticide at low toxicity (pyrethroids), limited to the area located at least 20 m from the lake and only during periods of massive swarming; ii) installation of 200 bat boxes, uniformly distributed, has been successful and raised awareness towards the protection of the bats, thus emphasizing their ecological role; iii) diversion from inhabited areas by means of outdoor lighting, called “tofo-lamps” (no. 150), set up along the littoral zone. This technique exploits the sensitiveness of numerous insects to photoreception. In respect to the negative environmental impact owing to the spreading of insecticides, tofo-lamps and bat boxes have less impact on the environment. The use of the integrated control at Lake Trasimeno represents a remarkably innovative method for limiting the largest swarms of the chironomids in anthropic areas. This approach should be taken in due consideration in management programs aimed to protect the integrity of lacustrine ecosystems.