An adult navel orangeworm moth. Females lay eggs on almonds, and the larvae that hatch from the eggs feed on the nuts.

For the past 50 years, a moth known as the navel orangeworm (Amyelois transitella) has been the number-one insect pest of almonds. Females lay eggs on the almonds, and the larvae that hatch feed on the nuts.

In addition, the larvae wreak further havoc by inadvertently spreading spores of mold-forming Aspergillus flavus or A. parasiticus fungi, which can produce cancer-causing compounds known as aflatoxins. Almond processors spend millions of dollars every year inspecting harvested almonds to ensure that they do not contain unsafe levels of these toxins.

Now scientists at the USDA’s Agricultural Research Service have developed a promising new combination of all-natural compounds to lure navel orangeworm moths into traps.

According to team leader John J. Beck, preliminary tests indicate that the experimental lure is at least seven times more powerful than the most commonly used alternative. The new lure’s effectiveness is due, at least in part, to its ability to attract both male and female navel orangeworm moths, which the conventional lure cannot do.

Growers and their pest-control advisors typically use traps hung from almond tree branches to detect incoming navel orangeworm moths and to monitor their numbers. Then they use the information to determine the best time to apply insecticides. The new lure may provide a more accurate picture of moth numbers within an orchard.

The new lure is a unique, carefully-researched blend of five natural chemicals, known to scientists as aromatic volatiles. Three of the chemicals are emitted by almond trees from damaged almond husks. The other two are emitted by the spores of fungi that may dwell on the almond trees.

Beck’s team used leading-edge techniques to collect, isolate, identify, and measure the compounds, and used electroantennograph assays to select and compare finalists. In the future, they plan to tailor the lure to work effectively in walnut and pistachio orchards.

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– New Lure May Help Growers Combat Almonds’ No. 1 Insect Pest