Washington State University Cooperative Extension

Areawide IPM Update

The Newsletter of Pheromone-based Orchard Pest Management

Vol. 1, No. 7 -- July 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.

Summer Horticultural Oils

All orchardists are familiar with the use of spray oils in the dormant or delayed dormant period for the control of insect and mite pests. Grower interest and experience with their use in the post-bloom, foliar period has increased in recent years, and several research projects are investigating this use further.

There are a number of reasons for this increased use and interest. Oil refiners have formulated a class of high-quality oils specifically for agricultural use, called horticultural mineral oils, that optimize their insecticidal properties and minimize the risk of phytoxicity. Examples of these oils include Orchex 796 (Exxon), Saf-T-Side (Monterey Chemical) and SunSpray Ultra-Fine (Mycogen). Spray oils are effective against a range of orchard pests and pest resistance to spray oils has never been observed. In addition, spray oils are minimally disruptive of biological control, with no residual effect on most natural enemies, and pest resurgence following application is uncommon. For these reasons, spray oils often are a good fit with soft pest control programs, such as those using mating disruption for codling moth control.

Of course, there are limitations and concerns with the use of spray oils, particularly during the foliar period. Fruit marking and leaf damage have been seen with some oil applications. Some fruit varieties, such as Anjou pears and Newtown apples, are more susceptible to oil damage. Certain spray materials, like Captan or Morestan, cannot be applied soon before or after oil sprays because of the risk of damage to foliage and fruit. Trees are at more risk of damage when treated with oil rates that are too high, during high temperatures, or when trees are stressed. Concerns have also been raised with the possible long-term effects on tree vigor, bloom and fruit size with the use of summer oils over many seasons.

Foliar oil sprays have been used on pears in California and Southern Oregon for more than 20 years, primarily for the suppression of pear psylla and spider mites. Dr. Peter Westigard of Medford, Oregon, has worked for many years with summer oils in the development of a soft pesticide program for pears. In the 400 acre Codling Moth Areawide Management site in the Rogue River Valley in southern Oregon, three spray oil applications are used together with mating disruption for codling moth control. These applications also contribute to good control of psylla and mites. To achieve this control, Orchex 796 is applied at a 1% concentration in 200 gallons/acre at 200°D, 400°D and 600°D following codling moth biofix. To avoid damage to fruit or foliage, oil sprays are not applied later in the season or when temperatures exceed 80 F. Oils are only applied under good drying conditions. Growers also take care to maintain good agitation in the spray tank and check to make certain that the oil emulsifies. Studies in Washington State have shown that oil sprays were able to further reduce codling moth damage in mating disruption blocks by 50% or more. These applications were timed to prevent the development of codling moth eggs by essentially smothering them with the oil. Applications of 1% oil to Red Delicious in Washington, and the same rate to Gala, Fuji and Braeburn in southern Oregon, have provided supplemental codling moth control without fruit or leaf marking.

Foliar oil sprays have provided control of other pests as well. Leafrollers have been suppressed with oil applications aimed at codling moth. The oil sprays reduced leafroller damage by up to 95% in some cases. Oil is thought to be effective against the egg stage, although effects on larvae or even adult behavior are possible. A 1% oil application has looked good in the field but poor in lab bioassays; further research in 1996 may make clear how to best use oil in the control of this pest. Control of white apple leafhopper has been good with 1% oil applied against first generation nymphs. Optimum timing appears to be when fifth instar nymphs appear. There is work to show that oil is quite effective in controlling tentiform leafminer, when applied at the pink stage of apple bud development after egg laying has begun. Orchex 796 sprayed at the 1% rate reduced first generation mines by over 95%, probably by deterring egg-laying as well as being ovicidal. Summer oil applications for mite control provided good knockdown of European red mite but also reduced populations of the predatory mite, T. occidentalis. Foliar oil applications have been studied for the control of powdery mildew on apples. Applications made repeatedly in July and August showed fair-to-good control under heavy disease pressure, with no leaf damage seen.

Research in Washington in 1995 focused on establishing the limits of oil applications on apples and pears. Three different oils were applied at both 1% and 2% rates in three different spray schedules: early summer, late summer and full summer (up to eight treatments). 1996 work will use two oils (Orchex 796 and Orchex 692) at 1% and 1.5% rates. Codling moth work will compare two versus three oil sprays per generation, timed prior to egg hatch. Leafroller studies will compare two and three spray programs, timed for oviposition. Effects on leafroller eggs, larvae and adult behavior will be studied in the lab. The horticultural and physiological effects of oil will also be studied, focusing on Delicious and Fuji apples and Bartlett and Anjou pears.

Summer horticultural oil sprays will not, in most cases, provide the degree of control with one spray that we have come to expect from most conventional insecticides. They will provide a useful tool for controlling or suppressing many orchard pests, particularly in orchards using pest control programs that preserve natural enemies. Growers using codling moth mating disruption or producing fruit organically will be among the first to find benefits in summer oil use. Further research will hopefully clarify how best to use summer oils to allow them to be used more effectively, widely and safely.

SUMMER TOURS are coming soon to a CAMP site near you!!

These are excellent opportunities to learn about pest control developments at each site and speak with the growers, consultants and researchers involved:

Carpenter Hill -- July 11, 1996
The tour of this site will begin at 8:00 AM at the Southern Oregon Research and Extension Center in Medford. For directions, call (541) 772-5165. The tour will conclude at noon for a barbecue lunch (yum!).

West Parker Heights -- July 16, 1996
This tour will begin with a visit to the 460 acre CAMP site and will be followed by a stop at the SARE (Sustainable Agriculture Research and Education) block in the Peters orchard, a multi-year project involving six sites in which Red Delicious are being produced without broad-spectrum insecticides. Following this, researchers from WSU-TFREC in Wenatchee will speak about other research being done in the Yakima Valley. For the tour, meet at the USDA Yakima Agricultural Research Lab, at 1:00 PM. To find the lab, take exit 44 from I-82, south of Yakima. Head east 0.6 miles from the exit to the Yakima Valley Highway. Turn right at the stop sign, going south 1.3 miles to Konnowac Pass Road. Turn left and go 0.3 miles to the lab. Parking is limited, so carpooling is recommended. We will travel from here to the sites.

Howard Flat -- July 18, 1996
The tour will begin with stops at two sites within Howard Flat, and finish with a visit to the SARE site at Twin WW Orchards. Meet at the Howard Flat information board at 2:00 PM. To reach this site, drive 3 miles north of Chelan on Highway 97 Alternate, and turn left at the sign for the Chelan Municipal Airport. Stay on this paved road for 0.6 miles; the information sign will be on the left side of the road.

Lake Osoyoos -- July 25, 1996
The field day for this CAMP site will meet at the John Biele Orchard at 1:30 PM. To reach this site, take High-way 97 to Oroville, and turn right on Central Ave. (at Chevron station). In 0.4 miles turn left on Cherry St.; follow signs to the Oroville Airport. After 0.8 miles turn left on Eastlake and proceed 3.4 miles to the meeting site.

CAMP Site Profile: Carpenter Hill

The Carpenter Hill site is located near Medford in the Rogue River Valley of southern Oregon, a region known for the production of high quality pears. This site in 1996 totals 400 acres, of which 360 are in pears and 40 in apples. Thirteen pear cultivars are grown, with Bosc, Comice and Bartlett-types (Bartlett, Red Bartlett, Starkrimson) as the main varieties. Tree ages range from newly-planted to over 60 years old. Most blocks are in the 200-300 trees/acre range, with some young pear blocks planted at over 500 per acre. Gala, Fuji and Braeburn are the apple varieties within the site. All are young (less than six years), planted at higher densities and use a support system. The Carpenter Hill site is relatively flat and is surrounded by other orchards, primarily pear.

In 1994 a pilot program was begun on about 80 acres, using both codling moth mating disruption and post- bloom applications of horticultural oils. In 1995 this area was incorporated into the new CAMP site of 300 acres. An additional 100 acres, including the first apples, joined the project in 1996. Six pear companies participated the first year, bringing in eight orchards and 32 separate pear blocks. Laura Naumes was hired as the local coordinator. Extensive monitoring of pests and natural enemies was done under the direction of Rick Hilton and Phil Van Buskirk of the Oregon State University-Southern Oregon Research and Extension Center. They also provided control recommendations to the participating growers. Isomate-C Plus was selected as the pheromone dispenser, and was applied throughout the site at 400 dispensers per acre.

This CAMP site has built upon earlier experiences with selective, soft pest control programs in this area, led by Dr. Peter Westigard of OSU-SOREC. This selective program seeks to preserve natural enemies and reduce reliance upon synthetic pesticides, but has been hampered by a lack of non-disruptive controls. Interest in this program has been spurred by the increasing codling moth resistance to Guthion. The availability of mating disruption for codling moth control, together with the use of selective materials like Comply for psylla control and Savey or Apollo for spider mites, has made the use of soft control programs more feasible. The program on pears within the Carpenter Hill site begins with a dormant oil application, followed by an oil plus lime sulfur spray at delayed dormant timing. Isomate-C Plus pheromone dispensers are installed at codling moth biofix. An important and distinctive feature of this program is the use of horticultural spray oil in the post-bloom period. Orchex 796 oil is applied at a 1% rate in three applications: 200°D, 400°D and 600°D after biofix. These sprays are timed to suppress codling moth populations, and also provide additional control of pear psylla and spider mites, with minimal disruption of natural enemies. (For more information on horticultural spray oils see the accompanying article in this newsletter.)

The results of the first year of the Carpenter Hill project are encouraging. The growers participating spent on average about $90/acre less in control costs than in associated comparison blocks. Use of synthetic pesticides was reduced by about 80%. Almost 40% of the acreage received the control program described above with the addition of an organophosphate applied for codling moth during the second generation. Another 25% of the acreage skipped even this one OP spray. In addition, the CAMP blocks produced fruit with less damage from pests. Overall damage to Bosc averaged 0.8% in CAMP blocks versus 3.3% in conventional blocks. This was mostly due to a large reduction in pear psylla honeydew injury. Spider mite- caused leaf burn and defoliation was practically non- existent in project blocks but was severe in close to 15% of the comparison blocks. Damage from codling moth was low in both areas.

Several real or potential weaknesses with this program were also identified in 1995. In common with other CAMP sites, leafrollers increased in areas within the project; overall damage averaged 0.4%, with severe damage found in two blocks. Additional monitoring and treatments are being used in 1996. There was also an increase in sucking bug (box elder and stink bug) damage. These insects are difficult to monitor, and the basic control program provides little protection against them. Better guidelines are also needed for the monitoring of natural enemies and for interpreting the potential for biological control they represent. With codling moth there is a concern with the ability to predict damage with pheromone traps and to adequately control them along orchard borders. There is also the concern with this program that codling moth populations may be gradually increasing, requiring more broad-spectrum insecticide use. Finally, growers have expressed concern with the potential long term chronic effects of post-bloom oil applications, possibly reducing tree vigor/fruit size.

The 1996 season is well under way at this point. The growers are pleased to have gotten through a cool and wet spring with a good pear crop. Codling moth catches to date have been higher than last year. There has been more use of Guthion applied to borders and 5% of the acreage received a full cover spray. Leafrollers have been followed more closely and, where indicated, growers have responded with several Bt sprays. Growers and research center personnel are monitoring thoroughly as the advantages and dis- dvantages of this unique pest control program are explored for a fourth year.

CAMP Site Notes: late June

The Lake Osoyoos site has codling moth cumulative trap catch running 70% less than last year, averaging about 0.8 moths/trap so far. Many growers have applied two covers, with some opting for zero or one. The release of sterile moths from the SIR facility in Osoyoos, British Columbia began this year on June 24.

At Howard Flat, codling moth counts remain well below those of last year. Cover sprays are largely on, and preliminary fruit evaluations are showing few stings and almost no entries. Recent thunderstorm activity has some growers thinking of last years devastating hailstorm and crossing their fingers!

The West Parker Heights site has nearly completed first brood codling moth flight. Less than half of the blocks received a cover spray in this generation, and fruit damage checks are underway. Blocks using Checkmate- CM have installed the new warm-season dispenser the last week of June.

At Carpenter Hill near Medford, the final summer oil spray has been applied for codling moth, psylla and mite control. There has been significant leafroller flight in areas but intensive monitoring has not turned up any egg masses or larvae to this point.

The Randall Island site expects Bartlett pear harvest to begin in early to mid July, and a thorough fruit damage evaluation will be done then. Codling moth pressure is low at this point and fruit exams after the first brood looked very good.

The Ukiah, California, site has taken a conservative approach to codling moth control in its first year, and fruit damage is minimal. Two applications of Isomate-C+ have been made, the second being made in early June. This was supplemented in all blocks with a Guthion application.

The Newsletter of Pheromone-based Orchard Pest Management
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, 2 July 1996