Pear growers plead for help with pest
WSU can no longer dedicate a full-time scientist to work on pear psylla control.
PearPsylla early instar nymph and eggs.
Pear growers in Washington’s Wenatchee Valley are hoping that Washington State University will help them find ways to control their key pest pear psylla, so they can stay in business.
Last year, the pest got out of control in the late season, leaving trees sticky with honeydew and much of the fruit downgraded. Pickers don’t like to work in sticky trees, and growers are also concerned that when labor is short, they might have difficulty finding people to pick their crops.
Since WSU no longer has a researcher dedicated to pear entomology, the growers felt they had no place to turn for help.
“There’s no way we can operate in the pear industry without an entomologist on pears,” field horticulturist Fred Valentine told the Washington Tree Fruit Research Commission during its February pear research review.
Growers have been battling pear psylla since it was first discoverd in Washington State in 1939. Entomologist Dr. Everett Burts joined WSU’s Tree Fruit Research Center in Wenatchee in 1958 to work on pear psylla, which had by then developed resistance to parathion. Several other organophosphates, such as malathion, diazinon, and azinphos-methyl, which were introduced in the 1950s, controlled the pest for a time. But the pest has shown a remarkable ability to develop resistance to chemicals.
“We’ve had over 17 chemicals in my career of dealing with pear psylla control,” Valentine said, “We’re so close to losing this pear industry that it’s very frightening. If you drive up and down the Wenatchee Valley, you will observe the fact that we’re not controlling pear psylla. Trees are black from pear psylla honeydew.”
Honeydew is a sticky substance that forms on the nymphs. When psylla populations are high, honeydew can drip onto leaves and fruit and serve as a medium for growth of sooty mold, which can turn trees black. Honeydew on fruit can cause russet and make the fruit unmarketable.
Dr. John Dunley joined WSU in 1995 to work on pear entomology after Burts retired. Dunley left WSU two years ago to work in private industry. He is not being replaced.
Over the past several years, WSU has endured severe budget cuts. Five researchers have left the Wenatchee research and extension center lately, in addition to Dunley. Entomologist Dr. Elizabeth Beers, one of the five faculty remaining, has a small program screening new pesticides for efficacy against pear psylla.
Bob Gix, field horticulturist with Blue Star Growers in Cashmere, said the need for a pear entomologist is very real.
“Growers spend close to $4,000 per acre to produce a crop of pears, and that $4,000 is put at risk if they can’t get people to pick it because the trees are very sticky or if the fruit is marked and is not marketable,” he said.
Pear psylla is found in other areas, such as California, but Washington’s cold winters seem to toughen the insect and make it harder to control with pesticides, he said.
In Washington, prebloom treatments are considered key to successful season-long control. Psylla migrate out of the orchards in the winter. Growers apply a kaolin clay to the trees in the delayed dormant season to deter them from moving back into the trees. The insects don’t like the clay surface, and it dries out some of the eggs. Growers also apply Thiodan (endosulfan) in the delayed dormant season, but use of that product on pears will end in 2013. Gix said growers have used pyrethroids in the dormant period but, in his career, six to eight products have been lost because of resistance.
Cool, wet, windy weather last spring made it difficult for growers to get their sprays on, which made summer control so much harder. “We got behind the eight ball, and at the end of the year, we had more growers with sticky fruit than in many years,” Gix said. “It’s a numbers game. If you can knock the numbers down early in the year, it makes the rest of the season work easier.
“If we’re not able to control pear psylla, the pear industry’s pretty seriously damaged,” he said. “We’re slightly different from apple in that regard because we have an insect that pretty much can take us out of business. I think Fred is just reminding us that even if we have a [dwarfing] rootstock and even if we can control decay, we can’t get there without controlling pear psylla.”
Dr. Dan Bernardo, dean of WSU’s College of Agriculture, Human, and Natural Resources, said WSU does not have the resources to hire personnel to work on single commodities. Bernardo said the focus today is much more interdisciplinary than in the past, and WSU has six research entomologists based in Prosser and Wenatchee who are expected to work with the specialty crop industries to address their concerns.
“I think having a pear entomologist doesn’t fit how we need to serve the industry nor how our faculty need to compete federally and regionally for funds,” he said. “We’re just not going to hire a pear specialist—or a raspberry specialist—in entomology. They need to be able to work across commodities and be responsive to the industry.”
Dr. Jay Brunner, executive director of WSU’s Tree Fruit Research Center, has since discussed the options with pear industry representatives. Dr. Peter Shearer, research entomologist at Oregon State University’s Mid-Columbia Agricultural Research and Extension Center in Hood River, who works with pear growers in Oregon, took part in the discussions.
The scientists are working with the industry to prioritize some researchable topics and draw up research proposals to obtain funding. Brunner said it’s possible that a postdoctoral scientist could be assigned to Wenatchee to work with Beers, Shearer, and scientists at the U.S. Department of Agriculture in Yakima, who are working on pear psylla management.
Shearer told the Good Fruit Grower he believes an integrated approach is needed to address pear pest problems. This would include using different products at different timings, enhancing biological control of key pests, using mating disruption for codling moth, and, ultimately, breeding psylla-resistant pear varieties.