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In the News

January 26, 2006

Pruning back on spraying pests in dried plums

Breakthroughs from a well-orchestrated effort among agencies, pest control advisers, growers, and farm advisors resulted in new ways to control plum aphids with minimal insecticide spraying, and also earned the group the “2005 IPM Innovators” award from the California Department of Pesticide Regulation (DPR).

   Sooty mold can disfigure fruit.

Sooty mold that grows on honeydew secreted by aphids can disfigure fruit.
Photo by Jack Kelly Clark

To date, the California DPR has given out more than 85 Integrated Pest Management Innovator awards to honor California organizations that emphasize pest prevention, favor least-hazardous pest control, and share their successful strategies with others.

Information about the Integrated Prune Farming Practices (IPFP) team’s effort is found in the Prune Pest Management Guidelines and the Year-round IPM program on the UC IPM Web site. The research shows that many dried plum orchards do not need annual dormant season pesticide treatments for scale or peach twig borer control; prune aphids can be controlled with very low rates of insecticides, and prune rust treatments are not needed as often as previously believed.

Aphids can cause serious damage to dried plums. They can build up in large numbers on the undersurface of leaves and cause them to become slightly curled and stunted. High populations can weaken trees, retard growth, and reduce sugar content of fruit. Honeydew dropping on fruit can also cause fruit cracking.

Pest Control Adviser (PCA) Jed Walton was part of the IPFP group. He collected research data from field scouts to see if using reduced-risk pest monitoring practices is effective for dried plums. Now he’s taking these successful techniques to his growers in Gridley.

Walton tracked research data under the direction of Butte County farm advisor Bill Olson from 2000 until 2004, when Olson retired. Big Valley Ag Services then hired Walton as a PCA. The company has enrolled 17 prune growers to follow the IPFP monitoring program.

"Although DPR gave the award to the IPFP program leaders, growers and PCAs are partners in this effort,” says UC Statewide IPM Program advisor Carolyn Pickel, who together with Olson, led the project research behind the guide.

“We monitored 25 to 30 orchards statewide for four, five, or six years to determine the pest population level at which treatment is necessary to prevent economic loss,” says Pickel. “Since prunes are considered a minor crop by pesticide registrants, they have less insecticide options and will face fewer pesticide registrations in the future. We encourage alternative practices such as replacing organophosphate insecticides with oil, along with precise irrigation monitoring to manage runoff, and using cover crops to improve water penetration and decrease pesticide runoff.”

Walton says the IPFP monitoring guidelines have been well received by growers in his area. “In many instances, the monitoring practices will save growers money by reducing chemical and fertilizer use without sacrificing crop quality or crop load,” he says. “However, sometimes the opposite is true, and you discover that the crop is suffering from not doing enough. Another benefit for growers, at least in my area, is that there are now programs available from the Natural Resources Conservation Service and other agencies that give growers incentive pay for following these monitoring guidelines.”

Through 2003, IPFP collaborators reported the program’s results at grower meetings, field meetings, commodity meetings, and workshops attended by 3,800 people. Pickel produced newsletters on the program’s progress and distributed them to 1,100 growers and 500 industry members. She also provided information for the UC Statewide IPM Program’s Prune Pest Management Guidelines and authored or co-authored nearly 20 publications on the project.

For more information, UC IPM offers a year-round IPM plan for prunes based on practices demonstrated in the IPFP program. UC IPM’s manual for stone fruits and tree fruit pest cards were used as training materials for the program.

The IPFP program, organized in 1998, is administered by the California Dried Plum Board and is a partnership involving the board, UC Cooperative Extension, DPR, the U.S. Environmental Protection Agency, The Nature Conservancy, farm advisors, pest control advisers, and dried plum growers.

IPFP collaborators include Bill Olson, Butte County farm advisor, emeritus; UC IPM advisor Walt Bentley; Rick Buchner, Tehama County farm advisor; Bill Krueger, Glenn County farm advisor; Wilbur Reil, Yolo County farm advisor, emeritus; Maxwell Norton, Merced County farm advisor; Franz Niederholzer, Sutter/Yuba County farm advisor; Ken Shackel, pomology, UC Davis; Steve Southwick, extension specialist, UC Davis; and Nick Mills, UC Berkeley entomologist, insect biology.


High-resolution image (248KB) "Sooty mold that grows on honeydew secreted by aphids can disfigure fruit." Photo credit: Courtesy of UC Statewide IPM Program, Jack Kelly Clark. Photos are for use with this release only. All other uses see Legal Notices.


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

Carolyn Pickel, Entomologist
UC Statewide IPM Program
Sacramento Valley
(503) 822-7515

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

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