The cranberry fruitworm, Acrobasis vaccinii Riley, is the most economically important pest of cranberries and blueberries in both the United States and Canada. It overwinters as a larva, later emerges and eats five to eight berries, and turns into an adult moth. When populations are high, the cranberry fruitworm can destroy entire crops.
But Agricultural Research Service scientists are getting closer to finding methods to keep this damaging pest under control.
They are using one of the important tools of modern pest management-insect sex pheromones. Pheromones make it possible for the sexes to find each other during mating season.
"So far, we have identified and synthesized the active ingredients in the cranberry fruitworm pheromone," says Leslie M, McDonough, a chemist at ARS' Fruit and Vegetable Insect Research Laboratory in Wapato, Washington. "We've discovered two compounds that, when mixed in the right ratio, are highly attractive to males."
The scientists say the new composition offers an important tool for use in future integrated pest management programs that might include a variety of anti-insect measures such as traps and predatory insect releases.
Lures containing the attractant compounds could be used to survey cranberry bogs and blueberry fields for fruitworms. And when pests were discovered, lures could again be used to monitor for any increase in infestation. Thus alerted, growers could begin insecticide applications before crops started to suffer damage.
But because some growers do not have such information, they now apply insecticide against the fruitworm without knowing if it is really needed. This leads to overuse of insecticides and increases growers' production costs.
Like other uses of pheromones, the lure could lead to mating disruption by so permeating fields with the scent that males become overwhelmed and unable to function.
"It was difficult to determine which of some 17 compounds extracted from nearly 500 female sex organs were the ones that excited males," says McDonough. "To find the most important ones, we suspended samples in tiny flight tunnels to see if males would fly upwind to locate our phantom female."
From that they were able to zero in on the two critical compounds.
After much testing, they discovered the preferred ratio between the two active ingredients ranged from 100:2 to 100:8, with 100:4 working best. Neither compound had ever been reported to be an attractant or pheromone component for any other insect species.
Lures were tested in blueberry fields in Michigan and in cranberry bogs in Massachusetts.
Several dosages were equally effective in attracting males for counting, as long as the compounds were in the 100:4 ratio.
McDonough, retired ARS entomologist Harry G. Davis, and ARS chemist Constance L, Smithhisler have applied for a patent for this research (Appl. No. 432923 ).
Annual value of the U.S. cranberry crop is about $200 million, with Massachusetts the leading producer, followed by Wisconsin. Other major states include New Jersey, Oregon, and Washington.
Blueberries worth close to $90 million annually are grown in all U.S. regions, but the leading states are Michigan, New Jersey, and Oregon. — By Dennis Senft, ARS.
USDA-ARS Vegetable Insect Research Laboratory, 5230 Konnowac Pass Road, Wapato WA 98951; phone (509) 454-6550.
"Sex Pheromone to Foil Cranberry Fruitworm" was published in the December 1995 issue of Agricultural Research magazine.