The Newsletter of Pheromone-based Orchard Pest ManagementVol. 1, No. 2 -- April 1, 1996
The codling moth pheromone (codlemone) was identified over 40 years ago. The concept of using it for mating disruption of codling moth was first proposed in the early 1980's. Only recently has it become a commercially viable option. This is due largely to improvements in the pheromone dispensers, allowing for the release of codlemone at adequate rates and for extended periods of time. Several types of dispensers have been used, in research and commercially. Codlemone has been loaded into rubber or plastic tubing, hollow fibers, and plastic membranes or wafers, as well as formulated into sprays.
There are four dispenser systems currently registered in Washington state: Isomate-C Plus (Pacific Biocontrol, Inc.), Checkmate-CM (Consep, Inc.), NoMate-CM (Ecogen, Inc.), and Disrupt-CM (Hercon, Inc.). The first commercial use of mating disruption came in 1991 with registration of Isomate-C, and more than 1500 acres were treated in Washington. In 1995, over 17,000 acres in Washington, and more than 25,000 acres in the western U.S., were under codling moth mating disruption.
Isomate-C Plus and Checkmate-CM are the only two products used extensively on a commercial basis. Isomate-C Plus (the "red rope") is generally applied at a rate of 400 per acre. 1995 research indicated that the dispenser continued to put out sufficient levels of pheromone for more than 140 days under Washington conditions. With this product only one application per season is needed. Checkmate-CM (the "white rectangle") releases pheromone at about twice the rate of the Isomate-C Plus dispenser, and the recommended number of dispensers per acre is lower, at 120-160 per acre. Checkmate-CM must be applied twice per season, as the dispenser releases pheromone for a shorter period. This dispenser is designed to last as long as 70 days. In 1995, Checkmate-CM ran out of pheromone approximately 60 days after the first application and 45 days after the second. A new Checkmate-CM dispenser has been engineered to extend the pheromone release period, and will be available in 1996.
The numbers of dispensers needed per acre for effective codling moth control is determined to a large extent by the CM density, or "pressure", within the orchard. Very low pressure orchards have maintained good codling moth control with dispenser rates of 200 per acre or less. Low pressure orchards should use 400 dispensers per acre, or can use lower rates (200 or less) if supplemented with insecticide treatment. Orchards with moderate CM pressure should use 400 per acre, and may need supplemental treatment with insecticides.
Proper dispenser placement is essential for mating disruption success. Most codling moth activity and mating occurs in the top third of the tree canopy. Dispensers need to be placed within the top two feet of the canopy, securely attached to limbs that will not be brought low by fruit load later in the season. Placing them within the tree canopy, and shaded by foliage, may improve their effectiveness by limiting exposure to wind, sunlight and high temperatures.
Codling moth mating disruption was used in all apple and pear blocks but, unlike the other CAMP sites, two types of pheromone dispensers were used here. Checkmate-CM, at 120 to 160 dispensers/acre, was applied to about 60% of the acreage, with Isomate C-Plus, at 400/acre, applied to the rest. Codling moth populations at the beginning of the year were fairly high in many areas, the result of a hailstorm in 1994 that so damaged the fruit that some cover sprays were dropped. A fairly conservative approach to codling moth control was taken in 1995, with most blocks receiving 2 or more covers and some additional sprays targeting orchard borders. At harvest, codling moth damage on average was low (0.2%), with over 90% of the blocks having less than 0.5% damage. There were localized pockets of damage exceeding 1.5%, most commonly on borders in the vicinity of prop or bin piles. In this high-pressure codling moth area, conventional blocks nearby that were monitored had an average damage of 0.8%, despite heavy cover spray use.
Pandemis leafrollers populations increased at Parker in 1995, similar to what occurred in the other Washington CAMP sites with the reduction in cover sprays. Early season sprays of Bacillus thuringiensis were made in many blocks but control was questionable, in part due to cool, wet weather at application. Fruit injury levels were generally low, with just two solid Golden blocks having fruit damage exceeding 1.0%, but enough of an increase was seen to warrant a thorough early season control program for leafrollers in 1996.
Other apple pests were generally not a problem, and increases in natural enemies (predators and parasites) were observed in many cases. Leafminer parasitism was higher in the CAMP blocks than in the nearby conventional blocks that were monitored. Higher numbers of aphid predators were also observed, although some blocks still received aphid treatments.
Parker has the most pears of the Washington CAMP sites (84 acres) and, together with the sites that are all pears at Randall Island and Medford, should provide good information on how to best use mating disruption in a pear pest control program. Psylla were well controlled in both the project and comparison blocks in 1995. Higher levels of psylla predators were found in the project blocks and post-harvest psylla populations remained much lower. In the next two years any improvements in biological control of pear pests will be closely monitored.
Broad-spectrum insecticides have been the primary tactic used to control arthropod pests of apple since their introduction in the late 1940s. Alternatives are available for control of the major arthropod pests attacking apple in the Northwest. Pheromones (mating disruption) can be used to control the key pest, codling moth, bacterial insecticides (Bt products) are effective against leafroller, and biological controls, mineral oils, insecticidal soaps, and cultural controls can combine to provide control for several other pests. These control tactics have been tested independently on various scales from small plots to whole farms, but their integration to produce apples without broad-spectrum insecticides has not been attempted. Growers often perceive that new technologies have higher risk of failure compared to conventional pesticides. Our goals are to use whole farm demonstrations to help growers 1) assess the benefits and constraints offered by new technology, 2) incorporate more selective controls, including mating disruption, insect growth regulators and biological control, into apple pest management programs and 3) identify shortcomings in monitoring programs and improve or develop new techniques for sampling pest and beneficial arthropod populations.
Demonstration orchards were established at six locations in 1995, three in northcentral Washington (Bridgeport, Chelan, Orondo), two in the Yakima Valley and one in Oregon (The Dalles). Each orchard was divided into a 10-acre conventional (CONV) block and a 10-acre no broad-spectrum insecticide (NBSI) block. Pheromones were used as the primary control for codling moth in the NBSI orchards. This treatment alone was as effective as conventional azinphosmethyl sprays at two sites. High codling moth densities at the other four sites necessitated supplementing the pheromone treatment with two other "soft" controls, mineral oil and parasitoid releases. This combination provided good control of codling moth in two orchards, but greater than 2% codling moth fruit injury was recorded at harvest in the other two NBSI orchards. At these latter two sites, adjacent CONV orchards sustained over 1% fruit injury at harvest. Most of the codling moth damage in NBSI blocks was found along the orchard edge. Insufficient control of codling moth in NBSI orchards was primarily associated with the inability of selective materials to control border infestantions of this pest.
Leafroller populations were well controlled in all of the CONV orchards but reached damaging levels in half of the NBSI orchards. Detecting the build-up of leafroller populations in time to control them with Bacillus thuringiensis (Bt) sprays proved difficult. Development of effective methods for sampling leafroller populations will be a major research component of the SARE project over the next two years. Other secondary pests were present at low levels in NBSI orchards. Natural enemies contributed to the suppression of many of these potential pests. Three species, white apple leafhopper, green apple aphid and tentiform leafminer, reached population densities that required intervention with insecticides in at least one of the CONV orchards. Detailed yield, packout and spray records have been kept for each pair of NBSI and CONV orchards and will be used to compare the economic risks and benefits of these two management programs.
We are looking forward to some new wrinkles in the project in 1996. In a major portion of four NBSI orchards (28 acres total), a promising new insect growth regulator, tebufenozide (Confirm ®), will supplement other codling moth and leafroller controls. This material is a new chemistry that stimulates an unsuccessful molt in the larva causing it to die of starvation within its old skin. In addition, large numbers of codling moth and leafroller parasites will be released at most sites. We hope you will attend our summer field tour of SARE sites. The tour will take place in late July or early August; the exact date and locations will be announced in this newletter.
-- Larry J. Gut, Jay F. Brunner & John J. Brown, Washington State University, Tree Fruit Research and Extension Center and Department of Entomology
Partial Funding provided by: Washington State Tree Fruit Research Commission, U.S. Department of Agriculture-Agricultural Research Service,International Apple Institute, and U.S. Environmental Protection Agency
WSU Cooperative Extension, Chelan County
400 Washington St.
Wenatchee, WA 98801