A newly introduced class of insecticidal compounds developed by the Agricultural Research Service (ARS) and cooperators offers safe and effective alternatives to conventional chemical insecticides.

The active ingredients are based on sugar esters that are natural chemicals secreted by wild tobacco plants to protect themselves against insect predators When certain insects rub up against and chew on the plants' leaf hairs, the insects become contaminated with the compound and die.

ARS entomologist Gary J. Puterka, working with industry cooperators, developed synthetic analogs, or look-alikes, of the natural sugar esters. He and colleagues then screened various synthetic sugar esters to find the most potent among them. While working at the ARS Appalachian Fruit Research Station in Kearneysville, W.Va., Puterka identified several of the new chemical forms that kill test insects instantly.

Puterka has been named a co-inventor on two patents that define the chemical structures of the compounds, as well as an environmentally sound process for their manufacture. One of the compounds, sorbitol octanoate, has proved less costly to produce than earlier forms patented, and is now undergoing the process of registration with the U.S. Environmental Protection Agency.

The analogs kill by breaking down the insect pests' outer waxy coating. Then the insects lose water and die from dehydration. The new class of compounds is unique among insecticides because their active ingredients do not leave a detrimental residue on surfaces to which they are applied. What's left over after application becomes inactive upon drying and rapidly degrades.

ARS is the U.S. Department of Agriculture's chief in-house scientific research agency.