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2006 Annual Report

UC Statewide IPM Program

Codling moth larvae bore into walnut
First-generation codling moth larvae bore into a walnut. Photo by Jack Kelly Clark.

Sex and insects are key to pest management

Wind tunnels that simulate a natural plume of air, a moving floor to give the illusion of flying, and insects listening to vibrations to signal courtship behavior are a few research methods entomologists described as part of “Orchard Integrated Pest Management Training” on March 17 in downtown Sacramento.

About 70 UC Cooperative Extension farm advisors and pest control advisors (PCAs) from Yuba City to Visalia came to learn about the latest information on how to reduce the number of insects and the serious crop damage they cause.a

The UC Statewide IPM Program sponsored the event, and UC IPM Advisor Carolyn Pickel spearheaded the effort. “I wanted to provide practical information to help field IPM practitioners make better pest management decisions in their daily lives,” she says. “Today, there are fewer farm advisors in the university system, and less applied research fieldwork is being done. We can learn a lot from experiments being done in the laboratory.”

Continued >> One of the main topics of the conference was mating disruption. Mating disruption makes use of an insect's own sexual scents, or pheromones, to confuse males and disrupt the mating process. Small plastic chips or ties are distributed in orchards to dispense the pheromone.

Farm Advisor Lynn Wunderlich from El Dorado and Amador counties says she attended the conference “to get a better understanding of mechanisms behind technology so we can apply those theories to our particular applications in the field.”

Wunderlich works with a lot of small-farm growers in the foothills. “It’s more challenging to get mating disruption thoroughly implemented because apples are planted next to pears, next to peaches. I’m dealing with smaller blocks of land and a diversity of crops. It really depends a lot on location, what neighboring farms are doing, and codling moth population levels. Maybe a grower has crops that aren’t terribly productive, and so it’s not economically feasible to fully implement mating disruption. Growers in my area need to use supplemental sprays on top of mating disruption.”

Stephen Welter, UC Berkeley professor; Larry Gut, professor and extension specialist for tree fruit entomology at Michigan State University; and John Dunley, associate entomologist for the Tree Fruit Research and Extension Center, Washington State University, spoke to a packed house of farm advisors and pest control advisors about their research results.

The advantages of pheromone mating disruption is best seen when the insect population is neither too high nor too low. Mating disruption cannot control very high levels without being supplemented with insecticides. At very low insect pressures, the use of mating disruption may not be worth the extra money.

Some other ways of dispensing pheromones are on the horizon, including fibers, flakes, and waxy dollops or splats. Research shows that the greater the number of point sources (microencapsulated beads), the more effective the mating disruption. Field practitioners balance this fact with the costs of using and making applications of higher point sources of pheromone with the population level of the pest.

Fibers are tiny, hollow tubes containing pheromone, which is released over a long period of time. The Scentry fibers are mixed with an adhesive and applied through a machine that uses centrifugal force to blow them into the tree. The machine is mounted on a tractor, and a shroud protects the driver from the fiber mixture.

The Disrupt MicroFlake (plastic laminate with pheromone inside) is another method. The flakes are mixed with an undiluted adhesive in an augur so they are thoroughly coated before being pushed into the air stream and up into the top third of the tree. The adhesive is washable while wet and is easy to work with, but sticks fast when dry.

Welter discussed his testing to develop management strategies for codling moth in walnuts. Carolyn Pickel, Frances Cave, Bob Van Steenwyk, Steve Sibbett, Joe Gant, and Steve Wulfert were part of the research team on this project.

The study showed superior results in suppressing codling moth in walnuts as opposed to pears. Researchers used a sprayable formulation of pheromone (Checkmate CM-F) because of the more closed canopy structure of mature walnut orchards compared to pears. Using this method in orchards with less mature or open canopies did not provide adequate protection against codling moth because materials exposed to sunlight break down quickly, diminishing their effectiveness.

Welter tested the fibers (mentioned above) by placing them in traps and measuring if they attracted moths. The fibers attracted moths for 30 days or longer. In walnuts, two applications of the fibers gave season-long control of codling moth. If issues of limited aircraft with specialized equipment can be resolved, then aerial application to larger walnut canopies may prove promising.

In a separate study, Welter and Cave used puffers as a supplemental control tactic along with insecticides for codling moth on 37 acres of walnuts in Glenn County, with trees that were 25 to 35 feet tall.

High-emission dispensers were developed to emit larger quantities of pheromone and use fewer dispensers per acre to cut down on labor costs. The only commercially available dispenser at this time is the Suttera puffer CM. The puffer uses a pressurized aerosol can that dispenses metered puffs of pheromone at fixed time intervals. Both researchers and growers are pleased with the first-year results of using puffers in walnuts.

Pickel says having speakers from Washington state is beneficial. ”New pesticides for apples are registered first in Washington because it has the most acreage nationally, and these pesticides are approved for use several years before California gets approval. Because of this, Washington usually applies pesticides several years before we do, and they can give us valuable information about their use.”

Dunley is looking at biological control agents such as parasitic wasps, and the mealybug destroyer, a lady bird beetle for grape mealybug. Also, he is examining some area predators such as earwigs and lacewings for their potential to attack targeted pests and spare other species. Dunley wants to develop a program that encompasses more than just codling moth control with pheromones. So, he focuses on insecticides that are more specific to the pest and not damaging to other beneficial arthropods in the system.

Attendee and PCA Gary Walker from Yuba City says the seminar gave him an opportunity to see what direction the research is going and pick up general knowledge. A PCA since 1979, Walker says, “We can see where there are similarities and determine how we can adapt and tweak their methods for our own use. Codling moth and peach twig borer are big issues for us. Less insecticide use and organics are necessary to get away from standard insecticides, and groundwater quality and nitrates are important considerations. It’s great to have the chance to see people working in agriculture who are staying ahead of the curve.“

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Cottontail rabbit
A cottontail rabbit. Photo by Tracy Ellis.

Preventing rabbits from causing serious plant damage

Cottontail rabbits cause extensive damage to ornamental plant nurseries in southern California by eating plants and damaging irrigation lines. With few methods to control the damage, UC IPM Advisor Cheryl Wilen and her field team used sophisticated technology to reduce the impact of rabbits.

Working closely with Pardee Tree Nursery in San Diego County and with funding from the California Department of Food and Agriculture Vertebrate Pest Research Advisory Committee, Wilen used Global Positioning System (GPS) technology to see how nursery practices and the incidence of rabbit damage are related, as well as to monitor the impact of experimental strategies to reduce their damage. The solutions are ingenious.

"California nursery growers report cottontail rabbits as the primary cause of breached irrigation lines and plant damage," says Wilen. "One large commercial nursery in San Diego County reported more than $10,000 each year in direct plant loss and nearly $12,000 annually for repairing irrigation lines."

It’s illegal to bait cottontail rabbits in California, so growers must look at other options to control them. The team studied nursery characteristics such as irrigation type, container type, planting density, canopy width and height, and the incidence of rabbit damage. Exclusionary and restricted fencing with and without trapping was then tested in high-damage areas. The team also developed and tested various materials to protect irrigation tubing.

"We determined that trapping is not effective because even when a moderate number of rabbits were trapped, there were still more rabbits entering the area from surrounding areas and causing damage," says Wilen.

Continued >> Wilen and her team experimented with electric and silt fencing. Silt fencing is a temporary sediment barrier consisting of a filter fabric stretched across and attached to supporting posts. It allows water to pass through, but traps soil particles. These types of fences are easy to install and remove. Results indicate that exclusionary fencing is an excellent temporary barrier, but it isn’t practical in some situations because it hinders normal nursery operations such as moving stock or getting equipment into the area. It could, however, be used in problem plant beds.

Wilen also recommends modifying spaghetti irrigation tubing by covering it with larger polytubing or using a system where the tubing hangs down rather than lying on the ground. Also, since radio telemetry (putting a collar on the rabbits that gives a radio signal for their location) verified that rabbits had a number of preferred hiding places, nurseries can reduce refuges for the rabbits by getting rid of piles of waste materials such as wood and pallets, or fencing them off.

"From our research, we now know which nursery production practices are most vulnerable to damage, and it gives us another tool to measure the impact of IPM experimental control strategies."

Wilen’s research partners are Tracy Ellis, Autumn Sartain, Ryan Miller, and Terrell Salmon of University of California Cooperative Extension, San Diego County.

Next article >> Weed management practices and rice

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Statewide IPM Program, Agriculture and Natural Resources, University of California
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