Toward a push-pull strategy against invasive snails using chemical and visual stimuli.

Four invasive Mediterranean snails, i.e., Theba pisana (Müller, 1774), Cernuella virgata (da Costa, 1778), Cochlicella acuta (Müller, 1774) and Cochlicella barbara (Linnaeus, 1758) cost $170 million yearly to the grain industry in Australia. Their impact is mainly due to their estivation behavior: snails climb on cereal and legume stalks to rest during summer, which coincides with harvest, causing grain contamination issues in crops such as wheat, barley and canola. Diverse management methods have been developed to regulate snail populations, with limited success. Our study investigates the potential for a push-pull strategy to divert invasive snails from cultivated fields. A "push" part (i.e. using a repellent stimuli) was based on the use of a chemical deterrent repelling snails from the cultivated field, and a "pull" part (i.e. using an attractive stimuli) was based on offering attractive estivation supports for snails to aggregate outside the cultivated field. First, artificial estivation supports of different colors were tested under laboratory and field conditions and showed that red supports were the most attractive for these snails. Second, different substances were tested as potential snail deterrents (garlic, coffee, coffee grounds, copper). Garlic extracts were the most powerful snail deterrent and were shown to effectively protect an estivation support and food source from snails under laboratory conditions. These results, which were highly consistent for the four species, illustrate the potential of a push-pull strategy against invasive snails in Australia. It is the first attempt to develop a push-pull strategy relying on both visual and chemical stimuli to achieve results, as well as manipulating the estivation behavior of a pest.