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Kairomones studied as better Navel orangeworm trap attractant

Western Farm Press

Beck and other ARS researchers have spent seven years developing a new lure – a blend of five natural kairomones semiochemicals. Unlike pheromone which is released by one sex to attract the other, kairomones are volatile compounds emitted by one species to produce a behavior from another.

A small plastic vial of kairomones in a standard delta trap tests the compound’s effectiveness.

Photo by Brad Higbee.

John Beck, U.S. Department of Agriculture research chemist in Albany, Calif., is leading the charge to build the proverbial better ‘mouse trap.’ Only in this case, it’s finding a better Navel orangeworm (NOW) attractant to use in trap monitoring.

“We’ve pretty much turned our full attention to just pistachios,” said Beck with USDA’s Agricultural Research Service (ARS).

“We’re trying to find the magic elixir which consistently provides effectiveness throughout the season.”

Beck and other ARS researchers have spent seven years developing a new lure – a blend of five natural kairomones semiochemicals. Unlike pheromone which is released by one sex to attract the other, kairomones are volatile compounds emitted by one species to produce a behavior from another.

Three chemicals selected for the experimental blend are produced by the almond tree. The other two are emitted by fungal spores, including Aspergillus flavus and A. parasiticus, found on almond trees.

Beck says a challenge with pistachio trees is emitting a much more complex group of volatiles than almonds and at much lower levels. The pistachio complex also is dominated more by terpenoids or terpenes than almonds.

“With pistachios, we looked for this same recipe (as almonds) but realized pistachios, for most of the pre-harvest life, do not allow many fungi to develop – a time we noticed when NOW semiochemicals are released,” Beck said.

“We have hypothesized that this inhibition of fungal development — not growth per se — is due to the large amount of monoterpenes, many of which have demonstrated antimicrobial activity in other systems.”

Based on three years of preliminary trials in commercial orchards, the new lure appears seven times more powerful than almond meal-based traps.

Pistachio growers currently have two types of NOW monitoring traps – each one with limitations. The pheromone trap uses female scents to attract nearby males. Since the lure is based on female pheromones, the lure does not alert users to female moth activity.

And, pheromone traps can be “shut down” by mating disruption, which involves blanketing an orchard with female pheromones to confuse male moths and interfere with the ability to find mates.

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