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Scientists unravel pest mystery

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First pear psylla pheromone identified by research team


By DAN WHEAT


Capital Press


Pacific Northwest tree fruit growers have used mating disruption to help control codling moth on apples for years. Now a huge step is being taken toward doing the same thing with a pear pest: the pear psylla.


Entomologists at the USDA Agriculture Research Service Laboratory in Wapato, Wash., and an entomologist at the University of California-Riverside have made the first identification of a pear psylla sex attractant pheromone.


It is the first pheromone identified in any of the psyllid insect family, said Christelle Guédot, one of the ARS scientists.


It opens a pathway to developing monitoring tools and possibly new strategies to control pear psylla, Guédot said.


The discovery was made in the winter of 2009, but research started in 2004, Guédot said. She made a presentation about it at the Washington State Horticultural Association annual meeting in Yakima on Dec. 8.


ARS entomologists Guédot, Peter Landolt and David Horton washed pear psylla, shook them in a pentane solvent, removed the pear psylla and analyzed 39 substances that remained in the solvent to find the pheromone, Guédot said.


The University of California-Riverside entomologist, Jocelyn Millar, helped identify the pheromone -- 13 methyl heptacosane or 13-MeC27 -- and synthesized it in the lab.


The work was difficult in that there are approximately 2,500 species of psyllids and no identified pheromone to use as a starting point for research, Guédot said.


Last year and again this year, the team will test release rates and different aspects of the pheromone's effectiveness in pear orchards near Yakima, Guédot said.


The ARS, on behalf of USDA, filed a patent application for the compound in September 2009 and intends to combine it with other attractants to produce blends for use in pheromone dispensers, bait stations or traps.


A product probably will be made available commercially, Guédot said, noting that could take years.


The discovery is exciting, but now the challenge is figuring out the best way to use it, said Tim Smith, Washington State University Extension tree fruit specialist in Wenatchee. He said there were many years between discovery and application of the pheromone as mating disruption for codling moth.


For at least 20 years, pheromone strips have been hung in apple orchards to confuse male codling moths and reduce their ability to find females, Smith said. It has been effective and is used with pesticides in conventional orchards and without pesticides in organic orchards, he said.


Smith said pear psylla usually appears more concentrated than codling moth and is a different insect. He said it could take time to determine the best methods of using pheromone with pear psylla.


Similar research is under way with psylla affecting potatoes, tomatoes, peppers, citrus and other crops, Guédot said.



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