Side effects of Aquatain AMF on non-target atmospheric air breathing insects

The fight against mosquitoes is necessary to reduce the spread of diseases and improve public health and the main strategy is the larvicidal struggle. Many active ingredients have been employed through the years, progressively less dangerous to the environment, moving from the organophosphates to IGRs and bacteria. In the recent years several companies started to develop larvicides which kills the insects mechanically instead of chemically. These products have the advantage to render almost impossible the development of resistance in mosquitoes and do not need to be registered as Biocide, which is a long and very expensive process. On the other hand, because the missing registration, studies about efficacy and impact on the environment do not need to be presented. The most famous of these products is Aquatain AMF, a monomolecular film (MMF) silicone-based liquid that reduces water surface tension and restricts mosquito breathing. Aquatain doesn’t present concerns when it is used in septic tanks or rainstorm drains, but what happens when it is applied in wide bodies of waters like ditches and swamps? The aim of the present study was to verify if the use of Aquatain and more in general of products able to reduce the surface tension, may have side effects on families of aquatic insects breathing atmospheric air. Insects belonging to the order Coleoptera (Dytiscidae and Gyrinidae) and the order Heteroptera (Corixidae, Gerridae and Notonectidae) were collected from wetlands and immediately moved to buckets 28×19×h14 cm containing 2 litres of water which were then treated with Aquatain AMF at the dosage defined in the label (1 ml/m²). The behaviour of the insects was then monitored, and mortality was recorded after 1, 2 and 24 h. Because of the strong killing effect on the insects, lower dosages (½ and ¼) were investigated to find a balance between the larvicidal efficacy and the respect for beneficial insects. The results of the study show that almost all the tested taxa are killed by Aquatain in nearly 2 h. Lower dosages reduced the rapidity of the killing which remained high after 24 h but incomplete as only Gerridae did not show any survivor. In conclusion, the use of monomolecular films in natural larval habitats must be very carefully evaluated for its consequences on beneficial insects.