Natural amino acid helps control potential citrus pest

01/23/2012 08:58:00 AM
By Vicky Boyd, Editor

tomato hornwormVicky BoydA naturally occurring amino acid is deadly against caterpillars that have alkaline guts, such as the tomato hornworm.

A naturally occurring component of protein may help control a potentially new invasive citrus pest, according to University of Florida research.

Entomologist Delano Lewis led a team that examined methionine, an amino acid, against the lime or citrus swallowtail.

The Asian native swallowtail was discovered in the Caribbean in 2006, and researchers say they're concerned it will hitchhike into the United States.

Because citrus swallowtails are not allowed to be imported, the researchers used the closely related giant swallowtail for their tests.

The researchers sprayed methionine on leaves, then placed swallowtail caterpillar on them.

Within two to three days, the larvae died.

The insect has to eat a treat plant part for methionine to be effective, so it wouldn't work on sucking pests, such as aphids, that feed on plant juices.

Earlier research also tested methionine on tomato hornworm larvae with the same results, Lewis says.

Although the team has yet to test it on other butterfly and moth larvae, he says he speculates it would work on all species that have an alkaline gut.

"We hope to go forward with tht and test it on other creatures," Lewis says.

The amino acid also has been tested on non-target species with no ill effects.

After all, Lewis says, methionine is added to livestock feed, so it's definitely not toxic.

Bruce Stevens, a University of Florida professor of physiology and functional genomics, discovered the pesticidal properties of methionine while cloning genes that regulate amino acide metabolism in 1998.

Methionine works by disrupting an ion channel that controls nutrient absorption in larvae with an alkaline intestine.

The actual mode of action is complex, which would significantly reduce the chances of a pest becoming resistant to methionine, Lewis says.

"So far, we haven't had any survivors," he says. "I wouldn't say it wouldn't develop resistance, but at this point, I wouldn't think so."

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