Environmentally friendly insecticides--an oxymoron? Not these sugar esters tested by ARS and university entomologists around the country.
They're lethal to mites and soft-bodied insects--whiteflies, aphids, thrips and pear psylla--almost instantly after contact. Then Mother Nature takes over, degrading the esters into harmless sugars and fatty acids. And they do little harm to insect predators and are completely nontoxic to animals and people. In fact, some are approved as food-grade safe.
AVA Chemical Ventures of Portsmouth, N.H., and ARS recently applied for a patent on the sugar esters. AVA hopes to have the first of these compounds on the market by the end of this year, pending registration with the EPA.
The sugar esters can kill up to 100 percent of the soft-bodied insects and mites they contact. And insects are not expected to develop resistance any time soon because of the way the esters work, according to ARS entomologist Gary Puterka at the agency's Appalachian Fruit Research Station in Kearneysville, W. Va. Puterka coordinated the studies nationwide and is co-inventor on the new patent.
Throughout four years of tests, the sugar esters have been more--or as--effective as conventional insecticides against mites and aphids in apple orchards; psylla in pear orchards; whiteflies, thrips and mites on vegetables; and whiteflies on cotton. Pear psylla have become resistant even to newer insecticides, according to Puterka, and mites are becoming resistant.
The drawbacks: The esters must come into contact with the insect to be effective, and they don't kill insect eggs. Like insecticidal soaps, sugar esters kill insects by either suffocating them or by dissolving the waxy coating that protects them from drying environments.
The concept of using sugar esters as an environmentally friendly insect control started about 10 years ago when ARS scientists in Beltsville, Md., found that the leaf hairs of wild tobacco plants exuded a sugar ester to defend itself against insects and other arthropods.