Mating disruption proves effective and cheap

In 80% of Washington's apple acreage, codling moth is still controlled by pesticides alone.

By Geraldine Warner

Over the past decade, there has been a revolution in tree fruit pest management. Mating disruption of codling moth was used on almost 40,000 acres of apples and pears in Washington State last year.

Dr. Alan Knight, an entomologist with the U.S. Department of Agriculture in Yakima, said Washington orchardists should be proud of having embraced mating disruption and reduced the use of pesticides, but he noted that 80% of the apple acreage in Washington is still being treated only with pesticides.

Pheromone dispensers for codling moth control were first registered in 1991. Growers who did not adopt the technique said the dispensers were more expensive and not as effective as the pesticide sprays they were using. But in recent surveys, the two major reasons growers are using mating disruption are the lower cost and improved control of codling moth.

What happened is the cost of mating disruption declined. At first, growers were paying about $130 per acre for dispensers. Now, the cost is down to about $60 per acre, partly because of competition among distributors, but also because many growers have been able to get by with fewer dispensers than the recommended rate of 400 per acre in the case of the Isomate C brand. Most are using 200 per acre and have integrated pheromone use into their pest management program. Frequently, pheromone dispensers are used with insecticides. Only 14% of growers using pheromones are not supplementing them with organophosphate sprays. A survey showed that almost half the growers questioned applied one cover spray or less (border sprays).

"A combination program is proving to be very effective," Knight said.

However, mating disruption needs to be refined further in order to encourage more growers to make the switch, he added.

Currently, most orchardists attach the twist tie dispensers to plastic bread bag clips to make the process of hanging them in the trees less time-consuming.

Knight said the cost needs to be lowered further by finding ways to avoid wasting pheromone. The pheromone needs to be used more effectively by adjusting the rates within the orchard, and developing technology to put additional pheromone on the edges of the orchards and to avoid releasing pheromones between the pest's generations. Problems caused by other pests, such as leafrollers, and the lacanobia fruit worm, also need to be solved; otherwise, growers still need to use harsh chemicals. Dual dispensers are available for codling moth and leafrollers, but they do not last the whole season.

A new way of putting pheromone in the orchard has been designed as an alternative to the hand-applied twist tie or foil dispenser. The puffer started out something similar to a bathroom deodorizer, but has been refined so that it can puff out pheromone at adjustable rates and frequencies.

The original strategy was to place puffers around the edge of the orchard and one puffer per acre in the interior, Knight said. Now, researchers are testing one puffer per 2.5 acres within the orchard and treating the border with hand-applied dispensers or sprayable pheromone.

Questions still to be answered are how the cost compares with dispensers, how well the puffers work compared with a half or full rate of Isomate C+, and how they can be used more effectively.

"I'm guessing we'll tell our kids how silly it was to tie dispensers to bread clips," he said.

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Mating disruption proves effective and cheap

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