Mating disruption helps control NOW in nut crops

Pheromone mating disruption is improving as an option for control of navel orangeworm in almonds, as competition among suppliers reduces the price and increases research into more efficient products.

Farm advisors say this alternative could become even more important for growers if resistance and regulation further limit chemical options for controlling orangeworm, by far the most important insect pest in almonds and pistachios.

"Mating disruption is becoming more affordable," said Emily Symmes, University of California Cooperative Extension integrated pest management farm advisor for the Sacramento Valley. "More pheromone companies mean competition and research into economical alternatives."

Symmes made her remarks in Williams during an IPM breakfast meeting, one of the series that brings UC researchers and growers together at rotating locations throughout the Sacramento Valley.

Navel orangeworm is a critical pest, both because of the direct damage it causes to the crop and because it increases the likelihood of infection by aflatoxin, a fungus so toxic its tolerance is measured in parts per billion.

There is only one navel orangeworm mating disruption product currently listed in the UC Pest Management Guidelines for almonds, but registrations are coming fast and there could be as many as four different pheromone alternatives available by the 2018 season.

Fresno-based Semios offers a package that includes both pheromones and a camera and computer-based monitoring program to trigger applications when the pest is present in the greatest numbers.

"They do the trapping, and have a camera in the trap that uploads to the cloud," Symmes said. "It uses less pheromone, but gets more out during the peak."

Trece of Adair, Okla., expects to have hand-applied meso-emiters, which are particularly suited for small acreages, of navel orangeworm pheromone registered and available for the 2018 season.

Vancouver, Washington-based Pacific Biocontrol got its aerosol pheromone product registered in mid-May, which was just a little too late for use in the 2017 season.

"Ideally, we like to get pheromones out there before the first flight, which is usually mid-March or April, and that will get you through October," Symmes said.

Bend, Oregon-based Suterra has a pheromone puffer that has been a widely used standard for many years.

The discussion of mating disruption came up at the IPM breakfast after Orland-based Big W Ranch manager Miguel Calzada asked if any new navel orangeworm materials are on the way.

"There are reviews going on, so we will probably have fewer materials, which highlights the importance of resistance management," Symmes said.

Altacor works on both navel orangeworm and codling moth, and is a particularly effective larvacide.

Many growers are also using the insect growth regulator Intrepid for control when the pest is at low numbers.

"Intrepid is great under lower pressure," said Franz Niederholzer, UCCE farm advisor in Colusa County.

There is one formulation of this material, however, that may affect important beneficial insects.

"The Delegate element of Intrepid Edge is pretty hard on the beneficials, like the six-spotted thrips," Symmes said. "If your navel orangeworm spray is hard on the six-spotted thrips, you can have problems with mites."

UCCE Kern County entomology farm advisor David Haviland has seen six-spotted thrips help control secondary pests late in the season in southern San Joaquin Valley almonds, and Symmes plans to monitor those results in the Sacramento Valley.

Growers need to find alternatives to pyrethroids, Symmes said,because there is a danger that if they are used too frequently to control navel orangeworm, the pest will develop resistance.

"People are trying to get away from the constant use of pyrethroids at hull split," Symmes said. "We haven't seen resistance to the pyrethroids, but we should be careful."

A pheromone mating disruption program could help to prevent resistance, and to provide an alternative if commonly used materials become ineffective.

"Mating disruption may be something to look at it," Niederholzer said. "It may be more expensive, but if we develop resistance to pyrethroids you may want to be ahead of the game."

It takes patience over a period of years to make pheromone disruption of navel orangeworm an economically viable option.

"It may be hard to pencil out for one year, but if you look five years down the road with large acreage, it might bring down the pressure," Symmes said. "We all know that mating disruption works; it's a question of getting the adoption rate up. Mating disruption is a proven technology, and the companies are always looking for plots for trials."

In the short term, almond growers can take solace in the likelihood that the weather gave them a break by helping to control their most important pest this season, as well as bringing enough water for a good crop.

"The navel orangeworm pressure is not as strong this year like it was the last couple years, when we didn't really have a winter," Symmes said. "Everyone has had an abundance of codling moths, and few navel orangeworms. Last year, we were hearing about insect pests; this year, it's about diseases."

"It's a pretty good year compared to the last three," said Calzada, who overlooks more than 5,000 acres of almonds and high density olives for Big W in Orland, and near Woodland.

(Bob Johnson is a reporter in Davis. He may be contacted at bjohn11135@aol.com.)