Washington State University Cooperative Extension

Areawide IPM Update

The Newsletter of Pheromone-based Orchard Pest Management

Vol. 1, No. 9 -- September 1, 1996

Cooperating agencies: Washington State University, Oregon State University, University of California, U.S. Department of Agriculture, and Chelan County.

Cooperative Extension programs and employment are available to all without discrimination.

Mating Disruption of Leafrollers

Leafrollers are becoming a pest in a growing number of orchards in the Western United States. Increased tolerance to pesticides is known to be partially responsible for this problem. The effective insecticides available can be expensive, disruptive of biological control, or both. Leafrollers often emerge as a problem in blocks where codling moth mating disruption is used, complicating pest control where a less disruptive control program is being used. An effective yet soft control method is needed, and one approach that is being investigated is the use of mating disruption for leafrollers.

The two principal leafroller pests in Northwest orchards are the pandemis leafroller (PLR) and the obliquebanded leafroller (OBLR). Their life histories are very similar, with two adult flights per year, occurring in June and in August. Both species have as the main component of their pheromone the same compound, a 14 carbon length acetate ( Z11-14Ac). Research in Washington has shown that use of this component alone in pheromone dispensers has provided similar reductions in pheromone trap catch for both species, equal to that of more complicated and specific blends that include additional pheromone components.

Research into leafroller mating disruption began in Washington in 1990. Drs. Jay Brunner, Larry Gut and Alan Knight conducted trials using dispensers produced by Pacific Biocontrol (the Hamaki-Con rope), Consep, and Scentry/Ecogen (the No-Mate spiral). Work in small plots (eight acres or less) with PLR showed that the Hamaki-Con dispenser, at 400 per acre, was able to maintain leafroller populations at low levels. In orchards with larger trees, even when initial populations were low, leafroller populations increased with successive generations. This trend held true with both PLR and OBLR. Where use of Hamaki-Con was combined with use of other controls, principally Bt sprays, no improvement in control was found compared with use of Bt alone. The results with other dispenser types were no better.

In 1995, Knight began leafroller mating disruption trials in larger, replicated 40-acre plots, using Hamaki-Con for OBLR control. Leafroller populations were maintained at low levels in several of these blocks without the use of supplemental Bt sprays, and fruit injury levels were similar to the check blocks where Bts were used. Moth catch in lure- baited traps in the disrupted blocks, compared with the check blocks, was reduced over 95% in 1995 and 80% in the spring of 1996, but many overwintering larvae were found in allLeafrollers, blocks. Further research at this large-scale trial is being conducted in 1996.

In 1996, there are over 200 acres in Washington treated with a new experimental dispenser from Pacific Biocontrol that contains both the principal leafroller pheromone component (Z11-14Ac) and the codling moth pheromone (codlemone). This dispenser is called either Isomate Special or Isomate Super (depending upon the precise leafroller pheromone blend) but is commonly called the "dual" dispenser, referring to the two pests for which it is intended. It contains nearly as much Z11-14Ac as Hamaki-Con, in addition to 100mg of codlemone. Midway through this season, the dual dispenser appears to be as effective in suppressing codling moth as the Isomate-C Plus dispenser, and better than the Hamaki-Con dispenser in disrupting leafroller flight. It is being evaluated in Italy for a second year on over 400 acres, and will be used again on an experimental basis in Washington in 1997.

A product being evaluated this season by both Brunner and Knight is a sprayable leafroller formulation produced by Ecogen. This product, called MEC-LR, contains 200 grams/liter of Z11-14Ac in a micro-encapsulated form and is applied with conventional spray equipment. Results in 1995 from small tree plots showed that at high rates (40 grams/acre) it provided good trap catch suppression for 3 to 4 weeks, equal to the Ecogen spiral or Hamaki-Con dispensers.

Research in 1996 will include work in larger plots and in large trees, where this sprayable pheromone should function even better by having more foliage area to retain the pheromone.

In the Eastern US and in Europe leafrollers are a fruit pest of equal or greater importance than codling moth, and research into the use of mating disruption has been ongoing for many years. The leafrollers studied include different species than those found as pests in the Western US but their biology and behaviors are similar. Use of pheromones for leafroller control has been most effective where population densities have been reduced to very low levels, in Europe usually by the use of insect growth regulators. While some studies on the use of mating disruption for leafroller control in Europe have been promising, it has not been adopted as a commercial control.

Leafrollers may be a more difficult pest than codling moth to economically control with mating disruption in Northwest orchards. Mating disruption is most effective in keeping populations at low levels, and much less effective in reducing high populations. The leafroller populations found in or near most orchards are considerably higher than those for codling moth, because leafrollers are not exclusively fruit feeders and have many native, non-orchard host plants. We are fast learning how to use mating disruption for effective leafroller control, after which we can determine if it can be used economically.

CONFIRM: A New Insect Growth Regulator for Orchard Pest Management

A new insecticide likely to be available for use next year in apple and pear orchards is CONFIRM®, an insect growth regulator produced by Rohm and Haas. CONFIRM's common chemical name is tebufenozide, and it has a mode of action unique among available insecticides. It is effective only against several lepidopteran pests, including leafrollers and codling moth. CONFIRM is an ecdysone agonist, mimicking the natural molting hormone found in insects. It initiates the molting process in the insect but doesn't provide enough information for the process to be completed successfully. After ingesting the material, the caterpillar usually stops feeding within a few hours and produces a new but poorly formed cuticle beneath its old one. Unable to shed its old skin, the caterpillar dies of dehydration and starvation within a few days.

This mode of action is unlike that of any other insecticide registered in the United States. Because of this, cross-resistance with other classes of insecticides is considered less likely. This should make CONFIRM an excellent addition to a resistance management program in orchards, particularly with the developing resistance of codling moth to other materials such as Guthion (azinphos methyl).

CONFIRM is primarily effective against larvae by ingestion, having little or no contact activity. Because it must be consumed, thorough coverage of the tree is critical. CONFIRM has shown good persistence in the field, with residual activity of several weeks or more. It has limited egg activity so sprays are timed for the presence of larvae. Although it has no direct effect on moths, it apparently has sub-lethal effects, possibly reducing the number and viability of eggs laid by exposed females.

CONFIRM is particularly suitable for use in orchard IPM programs because of its selectivity and low toxicity to non-target insects. It does not disrupt the biological control provided by parasitic wasps and predatory bugs, beetles, lacewings, spiders, mites and others, and is essentially non-toxic to honeybees. Its activity is limited to several lepidoptera species, including codling moth, several leafrollers and green fruitworm in apples, and beet armyworm, European corn borer, spruce budworm and gypsy moth, among others, on other crops. Leafminers on apples are partially controlled or suppressed by CONFIRM.

In addition, this new insecticide is practically non-toxic to humans, posing minimal risk to applicators, handlers and other orchard employees. It has moderate toxicity to fish and aquatic invertebrates, and low or no toxicity to birds and other organisms in the environment. It degrades easily in soil and water, and does not leach readily. In short, it is a fairly friendly insecticide towards the environment. In fact, the Environmental Protection Agency identified CONFIRM as its first candidate for its Safer Pesticide Program, speeding its progress through the registration process.

Research with CONFIRM has been conducted in Western US orchards by Dr. Bob Van Steenwyk in California, Dr. Helmut Riedl in Oregon, and Dr. Jay Brunner in Washington, among others. Their work has focused on its use to control codling moth, obliquebanded leafroller and pandemis leafroller. In general, codling moth control in these tests has been good except in high pressure situations, and leafrollers have been controlled well with this product.

It appears to be most effective against codling moth when the first application is timed for early egg hatch (250°D for first cover). Because CONFIRM has no adult activity, and must be consumed by larvae to be effective, it will not prevent fruit stings from codling moth under high pressure situations as well as some broad-spectrum insecticides, like Guthion and Penncap-M. However, larval mortality is high and the population density of the subsequent generation is reduced.

With leafrollers, larvae are also the stage targeted with CONFIRM. Timing is similar to that used for Bt applications, with the overwintering generation being controlled with sprays at pink and petal fall. As with codling moth, the mortality of larvae in the generation treated with CONFIRM has sometimes been less than that expected from organophosphate sprays, but population levels the next generation are typically very low, again suggesting strong sublethal effects.

CONFIRM has been has been used effectively in Europe for several years, encouraging the adoption of economical integrated fruit production programs. It is registered in Canada for apples, and received a Section 18 registration this year in several Eastern US states for the control of OBLR and tufted apple budmoth. The only tree crop with a full registration in the US at present is California walnuts. A full registration for apples in this country is expected in 1997. If that occurs, we will have available a valuable new tool for use in both pheromone-based and conventional orchard pest management programs.

CAMP Site Update: Late August 1996

The Howard Flat apple harvest has begun with the initial picks of Gala apples. Fruit size of all apple varieties is mixed, owing mostly to the cool post-bloom weather, but fruit is relatively clean and free of defects. Codling moth catch remains low except in about seven traps, many of which are in the vicinity of the one non-participating orchard in the project. Cover sprays for the second brood have been applied to less than 10% of the acreage. Leafrollers are present in a few limited areas. Significant pheromone trap catch has been seen in about 13 of the 175 blocks, and August surveys of shoot tips found less than 10 blocks that might need leafroller control. Fruit damage assessments from bins at harvest will provide key information about these and other pests.

Harvest of Galas has begun in the Lake Osoyoos project area. Initial fruit damage surveys so far show leafroller damage of about 0.1%, in contrast with last year when over 5% was found in some of these blocks. Leafrollers were the most serious fruit pest at this CAMP site in 1995 but appear to have been brought under control this year across the project. There are reports, however, of serious leafroller problems this summer in many conventional blocks in the Oroville area. Codling moth trap catch remains very low, with 95% of the traps showing no second brood catch. Sterile moth release will continue until mid-September. Leafhoppers are high in many blocks and some sprays are being applied for them.

Harvest is also underway in the West Parker Heights CAMP site, with Bartlett pears having been picked as well as some Goldens. Codling moth catch overall is low, although more moths are being caught in some areas than would be expected based upon the lack of first generation fruit entries. Some CM increase was found in traps near bins that had just been brought in. Catch picked up in some blocks treated with Checkmate dispensers. Analysis at the USDA lab showed that about one-third of these dispensers were close to running out of pheromone, so a third application was made. At this point, no cover sprays for second CM brood have been made. Some leafroller hot spots are found in the project, with feeding on terminals becoming more visible later in August. Bt sprays have been made in many of these blocks, with a few Lorsban applications as well.

Brad Higbee, coordinator for this site, has compiled a set of photos showing fruit damage by many pests, as it appears during the summer and at harvest. If you are interested in obtaining a copy of this set, or contributing photos, contact Brad at (509) 454-6564.

At the Carpenter Hill site the Bartlett pear harvest is nearly complete and harvest of winter pear varieties is underway. A hailstorm in early August in the Medford area hit this site particularly hard, causing substantial cullage. Assessment of harvested fruit at this point shows that codling moth control has again been very good. Where leafrollers were identified as a concern early this year and a focused monitoring and control program was implemented, good control was achieved. New hot spots of leafroller damage were identified in the CAMP site later in the season, with some fruit damage associated with them. Fruit damage from true bugs continues to be a problem in some areas, with stink bugs and box elder bugs the main culprits, and Bartletts may be harder hit than other varieties. There are few insecticide options for bug control in the selective control program used at this site, and increased attention to host plants and weed control may be needed.

Ted Alway, Editor
Phone: (509) 664-5540
Fax: (509) 664-5561
e-mail: alway@coopext.cahe.wsu.edu

Partial Funding provided by: Washington State Tree Fruit Research Commission, U.S. Department of Agriculture-Agricultural Research Service, U.S. Apple Association, and U.S. Environmental Protection Agency

WSU Cooperative Extension, Chelan County
400 Washington St.
Wenatchee, WA 98801

Wenatchee WA, 30 August 1996