This marks the second season that walnut grower Dave Taylor at Barngrover Ranch, Linden, Calif., is using pheromone mating disruption technology to help control coddling moths.
The battery-operated units are made by Suterra and marketed under the Puffer name. Each dispenser emits bursts of a synthetic pheromone at timed intervals to disrupt mating activity, causing male moths to follow false female scents, thus reducing their ability to locate females and breed. A delay in mating of just a few days can significantly reduce egg-laying by females.
This year, Taylor hung Puffers in 280 acres of Chandler, Sunland, Tulare and Vina walnuts. A 40-acre untreated block of Hartley downwind also benefited from the pheromone plume.
Because of concerns about the possible loss of conventional pesticides due to regulatory restrictions, Taylor began looking for alternatives about 10 years ago. He’s since tried several methods of pheromone mating disruption, including hand-applied dispensers and sprayable formulations.
“Some worked great, and some didn’t,” he says. Drawbacks ranged from a breakdown of the synthetic pheromones in hot summer temperatures to uneconomical treatment costs.
Using mating disruption to control codling moth requires a long-term commitment, Taylor says. He’s also learned the importance of regularly monitoring the effectiveness of the pheromone products.
“You need to have more traps and more eyes in the field than with conventional pesticides. You can shut down the traps with the pheromones, but that doesn’t necessarily mean you’ve controlled the population of the moths.”
That’s why he uses a pruning tower to check anywhere from 500 to 1,000 nuts for codling moth strikes after the first and second flights. But, because the traps aren’t catching any moths, it’s becoming more difficult to determine the peak for the flights. So, he uses data from conventionally-treated blocks to identify the different flights.
Puffers are located to dispense the pheromone plume over as much of the orchard as possible. The proper spacing of the dispensers varies within an orchard and from one orchard to another, depending on such factors as speed and direction of prevailing winds and spacing of the trees.
Typically, they are placed in a uniform grid pattern in the interior of the orchards and closer together on the edges, especially the upwind side.
Taylor places Puffers no more than 200 feet apart along the edges of the orchards to compensate for the small areas between adjacent trees on the outer rows where the plume doesn’t reach. Inside the orchards, he spaces them farther apart, ending up with one dispenser for every 1.8 acres for Chandler and Tulare, and one for every 1.9 acres for the other varieties.
Each Puffer has a 220-day supply of the pheromone. Taylor hangs them in mid- to late-March and sets them to dispense a plume every 15 minutes for 12 hours, beginning at 5:30 p.m. For maximum dispersal of the pheromone, he places the dispensers as high in the canopy as possible, up to about 45 feet above the ground.
While standing in the pruning tower, he throws a quarter-inch rope over a high branch. He then makes a loop to attach the Puffer, pulls it up into place, and ties the other end of the rope to the tree. He doesn’t take the units down until well after harvest in order to control any remaining moths.
To make sure the dispensers are working, he randomly checks them. After lowering one, he uses sight and smell to determine if a plume is being emitted. He also turns the clock on and off manually to verify that the timer is working.
Even though the cost of the pheromone treatment has been a bit more than conventional pesticides, the Puffers are already paying off, Taylor says. He now sprays only twice during the season — once to control sunburn and once to spray a growth regulator for mite control.
To measure the pheromone’s effectiveness, Taylor says, he sampled 5,000 nuts earlier this year and found only two codling moth strikes. The sampling included areas of the orchard where control once was the most difficult. In those areas, he found no strikes.
“Last year at harvest, codling moth damage was under .0003 percent,” he reports. “Out of almost 1.5 million pounds of nuts, we had only one strike. That’s an extremely successful rate and mitigates some of the extra expense of the Puffers. In the past, codling moths damage was about 2.5 percent to 4 percent.”