Washington State University Cooperative Extension

Areawide IPM Update

The Newsletter of Pheromone-based Orchard Pest Management


Vol. 2, No. 11  December 1, 1997

Inside this issue:

Web links:

...Ted Alway's Areawide IPM page

...USDA Yakima Areawide IPM page (with CAMP site descriptions)

...WSU-TFREC Entomology home page

...Index to Areawide IPM Update newsletters

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.


Tree Fruit IPM Workshops Planned

How we achieve effective and economical orchard pest control will be quite different within just a few years. Orchardists can expect to lose, as a result of the 1996 Food Quality Protection Act, many pesticides that have played key roles in their pest control programs, including most organophosphates, carbamates and compounds identified as probable carcinogens. These losses will be offset somewhat by the host of new compounds and approaches that are being developed and registered for apples and pears. Among these are insect growth regulators, other new chemistries, mating disruption and more. These new, developing pest management programs will require new knowledge, new skills and more training for consultants and growers.

To help in understanding these developments and to prepare for this not-so-distant future, a series of three all-day workshops will be held in January 1998. The workshops are titled "The New Face of Orchard Pest Management," and are jointly presented by Washington State University Cooperative Extension and the Washington State Horticultural Association. They will be held at the Cedars Inn in Okanogan on January 13, the Doubletree Inn in Wenatchee on January 14, and the Doubletree Inn in Yakima on January 15.

The morning will feature presentations by:

  1. Dr. Mike Willett and Dr. Wally Ewart of the Northwest Horticultural Council, addressing regulatory changes and the future availability of pest control materials with respect to the Food Quality Protection Act;
  2. Dr. Larry Gut of Michigan State University, discussing the use of mating disruption for control of codling moth and leafrollers; and
  3. Dr. Jay Brunner of Washington State University, presenting the latest information on new insecticides and their use in Northwest orchard pest management systems. The materials covered will include ConfirmĂ, ComplyĂ, SuccessĂ, and Sirene CMĂ.

Following lunch, Ted Alway of WSU Cooperative Extension will discuss the results of areawide control programs and then moderate a panel discussion with local consultants and growers that will address the opportunities, limitations and concerns that will be faced with these new and evolving orchard pest management systems. There will be ample opportunity for those attending to participate in the discussion and ask questions.

Extensive educational materials will be provided, as will lunch and refreshments. There will be 5 pesticide recertification credits available from the workshop. Attendance will be limited in order to facilitate asking questions and discussion, with no more than 150 attendees at any location. Advance registration will be $20 if received by the WSHA by January 5, 1998, and $30 after that or at the door.

To register, send your check payable to WSHA to P.O. Box 136, Wenatchee, WA 98807. Include your name, address and phone number with payment. Registration forms are also available from the WSHA office in Wenatchee and from Cooperative Extension offices in Wenatchee and Yakima.


Cover crops and orchard pest control

With the use of pheromone-based pest management programs, many growers and consultants hope to reduce the use of broad-spectrum insecticides and improve the biological pest control provided by natural enemies in their orchards. With this in mind, there is increasing interest and research in the use of special cover crops in the hope that they will improve biocontrol by attracting and supporting populations of beneficial parasites and predators. These natural enemies often include predators of aphids and mites such as lady beetles, lacewings, syrphid flies, predatory bugs (including Deraeocoris spp. and anthocorids), and parasitic wasps and flies.

Most orchards in the Pacific Northwest already have some type of cover in the alleys between the tree rows. For most growers, this cover is a predominantly grass sod (often with a healthy mix of dandelions and other weeds!). The cover crop serves many functions: it minimizes soil erosion and compaction, improves traction for equipment passage, improves water infiltration, suppresses or outcompetes many weeds, and reduces heat in the orchard and sunburn of the fruit.

Some growers, primarily organic producers, also use the cover crop as a source of nitrogen for the orchard trees, growing a legume such as alfalfa for the purpose. Some intentionally grow a cover crop in the tree row itself and not just between rows, with the intent of improving soil microbial activity, organic matter levels and nutrient cycling in this strip. Another potential approach would be to establish a low-growing perennial plant in the tree row, in place of an herbicide strip, that will suppress weeds but not be highly competitive with the trees.

For the additional benefit of increasing natural enemy populations, orchardists have planted specific mixes of plants that can provide habitat for beneficial arthropods. Prepared seed mixes are available commercially from several sources, identified as "Insectary Blend" or "Bug and Breakfast," among others. Generally, the mix includes a number of flowering plants that provide nectar and pollen sources to attract parasitic wasp and syrphid fly adults. Examples of these plants include buckwheat, alyssum, coreopsis, dill and yarrow. Other plants are included in the mix as host plants for an alternate prey (often aphids), on which the natural enemies can maintain or build their populations. Often planted for this purpose are rye, barley and dwarf sorghum, which host a number of cereal aphids, and legumes such as alfalfa, hairy vetch, or clover (including crimson, white or subterranean). Another way in which the cover crop can help with orchard pest control is through competition with the trees and reducing terminal or sucker growth, making the trees less susceptible to flush feeders such as aphids and psylla.

The management of the cover crop is important to its potential success in encouraging biocontrol. In order to have many flowers, mowing often needs to be delayed to let the cover grow to a sufficient height, and even then not cut as low as is common with a grass sod. To provide a continual presence of flowers, growers can practice alternate strip management, cutting only half of each row middle, or alternate row middles, if mowing is required. Some growers seed only every other middle with the insectary mix, and leave that middle largely uncut until harvest approaches. Another approach taken by some is to not sow an insectary seed blend but rather to manage the mix of broadleaf weeds that have already established themselves in the orchard; several weed species, including knotweed, mayweed and sowthistle, are fed upon by insects that are prey for predators like ladybird beetles.

Research with cover crops has shown mixed results in improving biological control in orchards. The BIOS (Biologically Integrated Orchard Systems) project with almonds in California╠s Central Valley has shown that cover crops can be an important tool in managing arthropods and natural enemies. Observations in 1967 in Ontario, Canada, apple orchards showed that parasitism of codling moth larvae was significantly higher with richly flowering understories than in those with few flowers. A California study ten years ago showed that over a two-year period an organic apple orchard with a cover crop of bell beans suffered 36% codling moth infested fruit, compared with 45% in a nearby clean cultivated block, not that this is acceptable in either case. Another study in 1982 compared biological control in four clean cultivated apple orchards with that in four others containing many flowering species, including wild carrot and parsnip. No improvement in biological control was noted for European red mite, leafminer, leafroller or aphids. The flowering blocks had more fruit damage from lygus, however.

Dr. Mark Brown of the USDA-Agricultural Research Service in Kearneysville, West Virginia, has for many years conducted studies of the effect of cover crops on biological control in apple orchards. Much of his work has focused on the concept of agroecosystem design, where cover crop composition and management are considered together with changes in other cultural practices and agricultural chemical usage. In one study, an IPM orchard with a cover crop of rye and red clover, with a 0.5 meter herbicide-treated bare strip of soil, was compared with a conventional orchard with a fescue ground cover and a 2.5 meter bare soil strip under the trees. Parasitic wasps were more abundant and diverse in the IPM orchard. The predatory insects present were more diverse in the IPM orchard, as the cover crop apparently provided a more stable food source for them. A second study compared conventional apple pest management with the use of selective pesticides and ground cover plantings in paired orchards in the US and four Central European countries. Biological control of orchard pests increased at all sites in the experimentally managed blocks, and some secondary pests increased in these blocks due to the reduced usage of broad spectrum insecticides. Dr. Brown concluded that with current economic realities the use of special ground covers and selective insecticides may not be practical for most growers, but this could quickly change if many broad spectrum insecticides become unavailable. A pear study in 1983 in the Yakima Valley found that planting a wheat cover crop in orchards increased populations of generalist predators such as lady beetles, lacewings, damsel bugs and bigeyed bugs which fed upon the various grain aphids that built up on the cover crop. However, the predators thought to be most important in providing biological control of pear psylla, Anthocoris spp. and Deraeocoris spp., were scarce in the cover crop. This is in line with other work that has shown that anthocorids are most often found in trees, not in the understory.

A limitation of cover crops in promoting orchard biological control may be that many natural enemies that are most effective within the trees are not found lower down in the cover crop, and high numbers in the cover crop will not necessarily result in adequate numbers in the trees. For this reason, there has been more research and interest in Europe in using windbreaks and hedgerows to encourage the buildup of natural enemies. In the Netherlands, windbreaks of black alder are planted around some orchard blocks. Alder aphids infest these windbreaks; predators such as lady beetles develop on these aphids and can move from the alders into the orchard if and when psylla, aphid or other soft-bodied insect populations appear there. The French have developed extensive publications describing suitable shrub and tree species for use in mixed hedgerows and the natural enemies they will attract. For example, an ash species is recommended because it is infested with an ash psylla upon which a population of psylla predators, such as anthocorids, can be maintained. Dr. David Horton and other entomologists with the USDA-ARS lab in the Yakima Valley have found high populations of anthocorids in the spring on willow, feeding on willow psyllids. The willow psyllid has only one generation per year and disappears by June; the entomologists are studying whether these predators will then move into pear orchards if the willows are grown alongside as windbreaks.

The native vegetation surrounding orchards can also be a source of beneficial insects. Studies in the Yakima Valley in the early 1980╠s showed that bitterbrush, a native shrub in Central Washington, is infested with a psyllid and can be a good source of psylla predators, primarily Deraeocoris. Ponderosa pine, which is frequently infested with a scale insect, can also support psylla and aphid predators. Consideration also needs to be given to whether the native vegetation is a source of pest insects such as stinkbugs and box elder bugs.

There is interest among many growers in using cover crops to promote biological control, and I have heard several accounts of the pest control benefits they have seen with their mixed, flowering cover crops. Investigations and grower trials continue in many locations. Many questions remain: are flowers needed throughout the season? Does the cover crop need to extend into the tree row? Does it need to even grow into the tree, providing a "ladder" of vegetation? What are the effects on populations of pest insects, like lygus bugs and cutworms?

The potential pest control benefits that suitable cover crops could provide may become more important with a decline in the use and availability of broad-spectrum insecticides and an increase in more selective, "ecologically-based" pest management programs. At this point, cover crops show promise but have yet to demonstrate consistent orchard pest control benefits.


SIR: Eradicating Codling Moth in British Columbia

The Sterile Insect Release (SIR) Program has completed its fourth year of sterile codling moth releases in southern British Columbia. SIR has the goal of eradicating, not just controlling, codling moth in the Province, and 1997 results show that it is well on its way to this objective. Unfortunately, the program once again faces financial and political troubles that may bring it to a premature demise.

The SIR Program operates a facility in Osoyoos, British Columbia, where it rears codling moth; production reached nearly 14 million moths per week in the summer of 1997. The moths, after being sterilized with radiation, are collected and distributed for release within orchards at a rate of 1500 per acre per week. The sterilized moths are released in such high numbers that they overwhelm the wild population and outcompete them for mates; generally, once a female mates she rejects any further attempts, even if the first male was sterile.

The first releases of sterile moths began in 1994 in Zone 1, following two years of efforts to reduce the wild population in the area. (Zone 1 extends from the U.S. border up to Summerland, and includes Creston to the east. Zone 2, where releases are planned to begin in 2000, extends from Peachland to Westbank and Kelowna. Zone 3 reaches from Vernon up to Salmon Arm, the northern limit of orchard region.) Little or no progress was made in 1994, as cleanup efforts were inadequate and the wild population remained too high. During the following two years, cleanup (spraying and host removal) and education efforts were intensified. Together with continued sterile moth releases, they succeeded in reducing the wild codling moth population to very low levels.

To effectively shut down mating with fertile moths, the program attempts to establish a ratio of at least 40:1 of sterile to wild moths. In 1997, this ratio was generally exceeded throughout the treated area of Zone 1. Ratios exceeded 40:1 on average for every week of the season, except for two weeks in late May and early June at the peak of the first codling moth generation. During second generation flight in August and September, the ratios ranged from 440 to over 900:1 for Zone 1 as a whole. Most growers applied only one cover spray in 1997, and many applied no sprays for codling moth at all.

Pheromone traps for codling moth are employed throughout the growing areas to monitor wild moth levels and determine the overflooding ratio. Catches have fallen dramatically each year. From a peak of 13 moths/trap/week in 1995, catches have fallen to a high of 2.6 in 1996 and down to only 1.3 in 1997. Over the last 10 weeks of monitoring in 1997 (early July through mid September), catch averaged only 0.09 moths per week across the 7600 acres of orchard surveyed.

Local eradication will be possible in many areas in 1998. Most growers in Zone 1 should have no need to apply cover sprays, outside of a few isolated hot spots. In general, moth populations remain the highest in the Creston and Osoyoos areas, although these areas also show the most dramatic population declines from pre-SIR days. Among the cleanest areas, where eradication in 1998 is likely, are Cawston, Naramata and Summerland. Releases will continue throughout Zone 1 the next two years, and then shift to Zone 2 in 2000 for a three-year period.

Releases will continue, however, only if the SIR Program itself continues. The SIR Management Board is seeking, by early November 1997, a financial guarantee of $4,000,000 for the remainder of the Program, equivalent to $600,000 per year. The Federal government appears willing to provide up to 50% of this amount, but funding from the financially strapped Provincial government is less certain. In addition, Dr. Ken Bloem, an entomologist and the director of SIR since 1992, will be leaving at the end of this year.

After some initial problems and setbacks, the SIR Program now appears to be fulfilling its promise of codling moth eradication in British Columbia. Lack of money may yet derail it, rendering the millions of dollars already invested useless and returning the Province╠s growers to the same pest situation they faced before the program began.

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.

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