The California Walnut Board is funding research on the efficacy of different lures for navel orangeworm (NOW) monitoring as an early warning system for the pest in walnuts.

Researchers are testing different lures, including a newer phenyl propionate (PPO) lure, as a complement to existing pheromone lures and Peterson traps (bait bags). “The pheromone lure can be helpful, but it can also be shut down by mating disruption, while the phenyl propionate is not,” said USDA-ARS Research Entomologist Chuck Burks, noting that the pheromone lure is specific to male NOW.

While the PPO lure can function on its own to attract both male and female NOW, current research shows that it works best in mating disruption blocks when paired with a pheromone lure.

Burks noted that there were small statistical differences in the performance of different traps and lures but that PPO lures could play a role, particularly in or near mating disruption blocks or as part of an areawide approach to NOW control.

“If you’re using trapping to guide your decisions, at this point I would tend to want to be using PPO with or without pheromone or bait bags instead of the pheromone by itself,” he continued. “The pheromone will give you high numbers in lack of mating disruption. In the presence of mating disruption, it will give you very low numbers, and it’s hard to know sometimes whether somebody in your area is using mating disruption or not.”

Burks also commented on the potential use of PPO in an area-wide IPM setting for NOW. With efforts ramping up for growers to coordinate management activities for NOW in nut crops, PPO could play a critical role in detecting presence of NOW.

“It’s a good idea in principle; the devil is in the details,” Burks said. “Some growers are concerned about a heavy-handed regulatory approach. In terms of trapping, if you have an area where NOW is a concern, ideally you have a trap that will give you somewhat similar numbers in the presence or absence of mating disruption, and I think that PPO does a good job of that when paired with pheromone.”

Burks hopes as area-wide IPM programs emerge for NOW, both bait bags and PPO with pheromone will be used, as each have their own advantages.