Issue link: http://read.dmtmag.com/i/34757
pheromone discovered PEAR PSYLLA Pear psylla has been a challenging pest to study. by Geraldine Warner S cientists in Washington State have identified the sex pheromone of the pear psylla, opening up the possibility of monitoring the insect with traps. This is the first discovery of a pheromone in any psyllid insect, and it surprised some in the research world who doubted that a psylla sex attractant existed. Pear psylla is a key pest of pears in the Pacific North- west. Nymphs and adults feed on phloem from the tree, and honeydew produced by nymphs drips or runs onto fruit, causing dark blotches or streaks. Excessive feeding and injection of toxic saliva by psylla can defoliate trees. Other psyllid species are also serious crop pests, such as the citrus psylla and potato psylla. Dr. Peter Landolt, research leader at the U.S. Depart- ment of Agriculture’s laboratory in Yakima, Washington, said researchers have worked for years to figure out first if the female pear psylla had a pheromone that attracted males, and then to identify it. When Dr. Christelle Guédot joined the lab in 2005 as a postdoctoral entomologist, other researchers there had recently established that female pear psylla must have a sex attractant, but a pheromone had not been identified. Guédot, who earned her doctorate at Utah State Uni- versity, tried several methods to identify a pheromone. In one test, pear psylla adults were put in an air stream in the lab and the air was filtered and analyzed with gas chromatography, but nothing showed up, perhaps because the quantities of chemicals were too minute. Guédot then had the idea of putting whole insects into a solvent and discovered that extracts from the cuticle of the females were attractive to males. When she compared chemicals extracted from males and females, most of the substances were similar, but she found one chemical that was much more prevalent on the female cuticle than on males and deduced that this must be the attractant. Dr. Jocelyn Millar, a synthesis chemist at the Univer- sity of California, Riverside, was able to produce the The newly discovered pear psylla pheromone is being tested in the field to find out how attractive it is to males. This mesh sticky trap has a septa of the chemical in the middle. chemical of interest, methyl heptacosane, for further tests. In the lab, Guédot established that that males were attracted to the chemical, though females were not, and that the chemical was as attractive to males as a live female insect. Field tests The chemical is now being field tested. Guédot and colleague Dr. Dave Horton put out sticky traps made of mesh with a septa of the chemical attached and proved that it was attractive to males but not females. They are testing different doses and various trap designs. Pear psylla adults have two different forms, winter- form and summerform. Some winterform adults leave Keeping things growing in the right direction! CONTINUOUS TRELLISLOK™ (Nut) The Continuous TrellisLok provides all the advantages of the TrellisLok (strap); however, if youuse theTrellisLokwith AgLok, your maximum diameter is limitless. BRANCHLOK™ Trellis & Fence Wire Anchor Embossed jaws grip the wire as it is inserted and prevent it from being pulled out. The wire is retensionable with a pair of pliers or a claw hammer. For yournearestdealer, contactAgFastat… 30 JUNE 2011 GOOD FRUIT GROWER Toll-Free: 877.552-4828 909.451-2299 • Fax: 909.593-8309 www.goodfruit.com christelle GuéDot, usDa