Insects destroy a very large fraction (thought to be up to 40%) of the global agricultural output and necessitate use of millions of tons of toxic insecticides and insect repellents that are environmentally unfriendly and can be harmful to other species including humans. Finding safe and effective repellents is, therefore, a top priority for agrochemical companies.
A significant breakthrough in finding safer alternatives has been made by a research team led by Anandasankar Ray at the University of California, Riverside. They investigated a series of naturally occurring structural analogues of N,N-diethyl-m-toluamide (DEET) [1], a widely used synthetic insect repellent that has been the subject of some safety concerns. One such DEET analogue, butyl anthranilate (BA, CHEBI:86192), has been identified as a potentially safe alternative repellent for the protection of fruit from airborne pests. As well as being relatively expensive, DEET is only meant to be applied to skin and clothing and cannot be sprayed directly on to crops. In a previous study, the team managed to identify the DEET-detecting olfactory receptors that cause the repellence in insect species [2]. Using a computer algorithm, the team were able to identify naturally occurring analogues of DEET with potential to be strong repellents. Several of these were subsequently approved by the US Food and Drug Administration as food additives.
In their current study, the team found that spraying blueberries with a 10% solution of BA, a flavouring and fragrance compound found in several fruits, provided nearly total protection for blueberry samples from a spotted wing Drosophila species, Drosophila suzukii. While most flies are attracted to rotting fruit, D. suzukii feeds specifically on ripening fruit making it a particularly destructive pest. As well as repelling the flies, BA also reduces their desire to lay eggs. Next, Ray wants to test how efficacious BA is in field trials, and if successful, to request approval from the US Environmental Protection Agency. He also intends to explore the potential of extending the approach for protection of humans and livestock from biting insects.
Pictured: The chemical structure of butyl anthranilate against a backround of blueberries. The background image is a detail from a Creative Commons licensed photograph of blueberries taken from Wikimedia Commons.