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September 29, 2004

Researcher grows sunflowers to protect peaches from pest

If IPM Advisor Walt Bentley has his way, sunflowers will offer a ray of hope in the battle against the oriental fruit moth by fostering its natural enemies.

   Lee Martin and Matthew Takeda use sunflowers to protect peaches from the oriental fruit moth.
  

Lee Martin and Matthew Takeda use sunflowers to protect peaches from the oriental fruit moth.
Photo by Walt Bentley

The oriental fruit moth is one of the most important pests of peaches and nectarines in the world. The female moth lays eggs on the fruit, and the eggs hatch into larvae which immediately attack the center of the fruit and feed around the pit, making the fruit unfit to eat.

The oriental fruit moth entered the United States on flowering cherries imported from Japan in 1916.  The pest quickly spread throughout the United States but did not reach California until 1942, prior to the development and use of synthetic contact poisons such as DDT.

Because available insecticides used prior to WWII were ineffective against this pest, the USDA developed a program of mass production of a parasitic wasp that effectively manages the oriental fruit moth in those states east of the Rocky Mountains. The wasp lays its eggs inside the pest’s larval stage, and then the wasp larva develops within, killing the pest. Once DDT became available, the parasite release program was stopped in most states.

The parasitic wasp does not survive without a host through the winter on oriental fruit moth, and it had to be reared and provided to farmers annually for release in orchards. The decline of this biological control program over the years was due to the easy use and effectiveness of new insecticides, which also killed the wasp.

But, if Bentley’s research bears fruit, the parasite will be able to live inside the sunflower moth caterpillars through the winter; reducing or eliminating the need to use insecticides on late- harvested fruit. “We’ve always had good management of the oriental fruit moth when fruit is harvested before August when we’re using mating disruption,” says Bentley. “Our problems occur with fruit harvested after July. There we often have used supplemental sprays. Macrocentrus may be able to eliminate the need for these sprays that occur late in the season.”

Control of the oriental fruit moth has contributed to the continued use of broad- spectrum pesticides in stone fruit in the San Joaquin Valley. Currently, pesticides are used along with mating disruption to manage this pest. But infestation has continued to occur in varieties harvested after August, necessitating the use of late-season insecticides. Since regulatory agencies have targeted these insecticides to be phased out because of surface-water contamination, an IPM approach is needed.

With support from the UC Specialty Crops Grant Program, Bentley has planted sunflowers on a 1/3-acre patch at the Kearney Research and Extension Center in Parlier, California, next to a peach orchard infested with oriental fruit moth. To date, his sunflower harvests have showed no damage from the pest.

Bentley’s research shows sunflower moths can help provide a higher population of the beneficial parasite earlier in the season while maintaining the oriental fruit moth at lower levels. Used in conjunction with mating disruption, parasites living in sunflowers planted near a peach orchard could control late-season infestations, eliminating the need for supplemental sprays.

Mating disruption makes use of the insect's own sexual scents, or pheromones. Researchers tie little chips with the female pheromone onto branches; the pheromone confuses the males and disrupts the mating process. The dispensers, which are acceptable for produce certified as organically grown, are placed in trees at the first sight of an oriental fruit moth in late February to early March. Current products will last into August, but fruit harvested later needs the additional help of parasites.

“Our experiments indicate that parasitism is greatest in late-harvested orchards from late July on,” says Bentley. “We believe this high level of parasitism will result in low survival for the oriental fruit moth in subsequent years, making mating disruption even more effective. We now plan to expand this biocontrol effort to late-harvested peaches and nectarines, combined with mating disruption, to reduce late-season insecticide sprays.”

Resources

High-resolution image (1.4MB) "Lee Martin, retired staff research assistant, and Matthew Takeda, student assistant, use sunflowers to protect peaches from the oriental fruit moth." Photo credit: Courtesy of UC Statewide IPM Program, Walt Bentley. Photos are for use with this release only. All other uses see Legal Notices.

Contacts

Stephanie Klunk, Communications Specialist
UC Statewide IPM Program
(530) 754-6724

Walt Bentley, Entomologist
UC Statewide IPM Program
Central Valley
(559) 646-6527

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