The fragrance of a new pesticide

You probably know methyl benzoate when you smell it. The natural compound’s wintergreen-spicy, floral-fruity aromas make it a popular ingredient in perfumes, soaps and shampoos.

Snapdragons and petunias emit methyl benzoate to attract bees for pollination. Insects also produce it as an attractant.

But not all insects like this compound.

Chemist Aijun Zhang, with the Agricultural Research Service Invasive Insect Biocontrol and Behavior Laboratory in Beltsville, Md., has found a new use for methyl benzoate: an environmentally friendly control for pests, including the spotted wing drosophila fly (SWD), an invasive species from Asia.

First found stateside in California in 2008, SWD has quickly spread across the U.S. and can cause significant damage to fruit crops, especially berries. There are currently few choices for controlling SWD. This research creates the possibility of a new bio-based pesticide based on an inexpensive chemical whose residue lasts a relatively short time in the environment.

Originally, Zhang was finding compounds in juice that attracted fruit flies.

“Rotted apples and other fruits usually attract flies, including SWD. We had isolated out several compounds that did that,” Zhang says. “But we found one compound — No. 19 — that strongly repelled SWD, and we later showed that it killed SWD as well.”

Compound No. 19 turned out to be methyl benzoate, a compound approved by the U.S. Food and Drug Administration for use in foods and cosmetics.

Zhang then tested methyl benzoate against other agricultural pests, including the brown marmorated stink bug (BMSB), diamondback moth, and tobacco hornworm. He found that it can kill all stages of these insects — egg, nymph, and adult — though it works better against smaller insects than larger ones.

Zhang focused first on SWD and BMSB because they are fast becoming important agricultural and household pests.

According to Zhang’s tests, methyl benzoate is 5 to 20 times more toxic to eggs of BMSB, diamondback moth, and tobacco hornworm than a conventional pyrethroid insecticide, a sulfur and pyrethrin mixture, and some organic products on the market.

Next, he is planning to test methyl benzoate’s effectiveness against fire ants, gypsy moths and other insects developing resistance to standard pesticides.

Zhang is also investigating whether low doses of methyl benzoate could control Varroa mites, the number-one problem of managed honey bees today.

A patent has been applied for methyl benzoate’s pesticide uses, and one company has expressed interest in it.

J. Kim Kaplan is a public affairs specialist in the ARS Office of Communications. Kim.Kaplan@ars.usda.gov