Fumigant Development for Killing Insects on Lettuce and Other Produce

Abstract

Abstract : When US lettuce shipped to Japan is found at destination to contain live insects, Japanese authorities require fumigation of the entire shipment. Fumigants now used kill the insects but cause extensive damage to the lettuce. This study was conducted to find new fumigants or fumigant combinations and to develop methodology for pre-export fumigation. Twenty-two naturally occurring fumigants were screened for efficacy against commonly found lettuce pests, aphids and lepidopterous larvae, and for phytotoxicity to the lettuce. The most promising candidate fumigants were acetaldehyde, ethyl formate, ethyl acetate, methyl bromide and a combination of methyl bromide and ethyl acetate. Of these, ethyl formate proved to be the most efficacious (99% kill for aphids) and the least phytotoxic (no detectable damage). Ethyl formate fumigated lettuce was then subjected to residue analyses (none detectable at < 0.01 ppm) and taste test panels for flavor changes (no detectable changes). Vacuum fumigation was conducted successfully on a commercial scale with 0.5% ethyl formate. Application for registration of ethyl as a fumigant has been submitted to the Environmental Protection Agency (EPA). Pending EPA approval, ethyl formate is recommended for use to fumigate US grown lettuce prior to shipment to Japan.