Investigators at the Agricultural Research Service (ARS) and almond industry in California have developed a new attractant to help almond growers monitor populations of the navel orangeworm moth. The attractant can be used to determine moth numbers during orchard treatments that are intended to disrupt the mating cycle of the moth or used as a monitoring tool during normal orchard operations.
Moth infestations not only damage the nutmeat but also aid the growth of mold-producing Asperigillus flavus and A. parasiticus fungi that can produce aflatoxin, a potential carcinogen. The female navel orangeworm moth is attracted to husks on maturing almonds that have split open, allowing larvae to burrow into the almond kernel and, in the process, transport fungal spores. The lure, developed by ARS chemist John Beck, PhD, at the ARS Western Regional Research Center in Albany, Calif., and his team, attracts both male and female moths. A blend of five aromatic volatiles, it is seven times more powerful than the almond meal formulation growers typically use.
“We are currently performing the first year of a season-long study with the blend in mating-disruption-treated orchards. We are comparing our blend’s efficacy to the standard almond meal-based lure in several commercial almond orchards in central California,” Dr. Beck says. “The results thus far are very promising.”
The Almond Board of California has adopted a Voluntary Aflatoxin Sampling Plan (VASP) program as part of a comprehensive approach to address concerns about aflatoxin, particularly within the European Union, one of its largest markets. The industry has instituted procedures to minimize aflatoxins at every stage of production and works with growers to reduce the potential for its growth by minimizing navel orangeworm damage.
“The almond industry has been very proactive when it comes to the safety of their product. The Almond Board of California and the California Pistachio Research Board are very supportive of research that helps to ensure the continued safety of their product,” Dr. Beck says.
His research is also exploring what appears to be a mutually beneficial relationship among the navel orangeworm, its almond host, and a semiochemical—an odor that communicates information between a plant and an insect—produced by fungal spores when on the almond host. He hopes to learn if the relationship extends to pistachios as the host plant and whether a new volatile or set of volatiles will act as an orchard-specific semiochemical of the navel orangeworm.
“Our goal is to pinpoint the alluring odors produced by the fungi and use them in monitoring traps that attract navel orangeworm moths,” Dr. Beck says.