Sex Pheromones and the Best Apples

Pheromones have proven tricky in some cases. They allowed farmers to grow ecological apples and pears for decades. The farmers have to place in their orchards hundreds of plastic dispensers spreading a sex pheromone, which attracts and disrupts codling moth mating. A new research made at the Agricultural Research Service (ARS) in Wapato, Washington, could improve the pheromone use promoting its spraying.

"Growers customarily hang the pheromone dispensers from tree limbs by hand-often 200 to 400 of them per acre. It's a laborious, costly affair," said Alan Knight, an entomologist with ARS' Yakima Agricultural Research Laboratory in Wapato.

Previous attempts of spraying pheromones were stopped by technological hurdles. Knight made an attempt in 2003, based on a 1999 result achieved while testing a fluorescent dye he had incorporated to a sprayable, microencapsulated pheromone product manufactured by a company from Bend, Oregon.

By employing the dye and a black light, Knight was able to examine microcapsule densities on tree leaves, finding that the codling moth pheromone's delivery could get better by employing ultra-low-volume (ULV) spraying.

This would lower water costs from 100 gallons to 1.25 gallons per acre and rise the microencapsulated pheromone's deposition rate by 6 to 10-fold.

Trials made in apple and pear orchards since 2003 revealed that ULV spraying 4 to 6 times a season stopped codling moth mating with the same efficiency as the hand-hung dispensers, fact assessed from captured-moth counts and decrease in fruit damage.

In 2005, Knight applied ULV spraying to the insecticide esfenvalerate, which decreased moth egg-laying by 95 %.

If not stopped, hatchling moth larvae bore quickly inside nearby fruit, which can no longer be sold. This species also attacks walnuts. Knight is checking reduced-insecticide amounts in combination with the pheromone. He even improved the sprayer itself by adding an electronic "eye" to head pulses of chemicals into the middle of a tree's canopy.