A phytoscreen identifies a garlic compound as a deterrent of mating  and egg laying in Drosophila and mosquitoes
There is a pressing need for new means of controlling insects that spread global infectious disease or that damage the world's food supply. The need is becoming more urgent as the ranges of many harmful insects expand with climate change. An extraordinary variety of phytochemicals, i.e. compounds produced by plants, activate the chemosensory systems of insects and influence their behavior. Fruits and vegetables present a source of potentially useful compounds that are inexpensive, safe, and environmentally friendly. Here we carry out a "phytoscreen" of 43 fruits and vegetables. We find that garlic potently deters both mating and egg-laying across diverse Drosophila species. Diallyl disulfide is identified as a compound in garlic that deters both behaviors. Mating and egg-laying effects depend on the sense of taste and on the cation channel TrpA1; garlic activates bitter-sensing neurons via TrpA1. Garlic also inhibits mating and egg-laying in the vector mosquitoes Aedes aegyptii and Aedes albopictus, and it inhibits mating of the tsetse fly Glossina morsitans, a vector of human and animal disease in sub-Saharan Africa. Finally, garlic exposure increases the expression of a set of genes in the Drosophila head including fit, previously found to encode a satiety hormone, which we find essential for the effect of garlic on egg-laying preference. Our results illustrate the utility of a phytoscreen in identifying compounds that inhibit essential behaviors of insects, and suggest applications to the control of insect vectors and pests.