Washington State University Cooperative Extension

Areawide IPM Update

The Newsletter of Pheromone-based Orchard Pest Management

Vol. 2, No. 9 -- August 1, 1997

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.


Stink bugs, orchards and pheromone-based pest management

by Peter McGhee, WSU Dept. of Entomology

Pheromones represent the most promising alternative tactic for controlling codling moth in pome fruit orchards of Washington. However, a pheromone-based pest management program (PBPM) will represent a drastic departure from current IPM programs. Control decisions will become more site-specific in response to local pest problems. One of the greatest challenges to a PBPM will be managing pests that reside outside the orchard and only visit or invade at specific times of the year causing damage. The most notable examples of these are true bugs in the families Miridae (Lygus sp.), Rhopalidae (boxelder bug), and Pentatomidae (stink bugs).

Stink bugs have caused serious crop loss to cherry, peach, nectarine, apple and pear. Control with insecticides is difficult. Stink bugs invade orchards late in the growing season when choice of chemical controls is limited by pre-harvest interval restrictions (PHI) considerations. Repeat sprays are often required because stink bugs continue to migrate into orchards.

Stink bugs are broadly oval and shield shaped with a large triangular plate in the middle of their back. Adult stink bugs are one-half to one inch in length. At least six species of stink bugs occur in native habitats in Washington. Three of these have been observed to cause damage to tree fruit crops in north central Washington; the consperse stink bug (Euschistus conspersus), the conchuela stink bug (Chlorochroa ligata), and the green soldierbug (Acrosternum hilare). Conchuela stink bugs live in dry land habitats, green soldier stink bugs live in riparian areas, and consperse stink bugs occur in both habitats. The consperse stink bug has caused the most economic loss in apple and pears.

Adult stink bugs over-winter in brush piles, rock outcroppings, and prop stacks surrounding orchards and in native vegetation from which they emerge in the spring. Consperse and conchuela adults feed on the mullein plant and bitterbrush throughout the summer. Females lay several clutches consisting of ten to twelve barrel shaped eggs from May through early July. The first generation of stinkbugs occurs when spring conditions remain cool, and warmer conditions may result in a second generation during late August or early September.

Injury to fruit occurs when mature stink bugs pierce the skin of the fruit and suck out juice. Apples attacked by stink bugs exhibit small dark depressions, primarily confined to the upper half of the fruit. The flesh beneath these areas appears corky and white to light brown. Stink bug injury sustained to apple is often misdiagnosed as the physiological disorder bitter pit and results in downgrading of the fruit. Injury to pear is more difficult to determine from the fruit’s exterior. Slight dimpling can occur where the insect has fed close to the stem where the fruit is narrow, but this symptom is not always observed. Injured areas beneath the skin are also corky and white. Often it is only the portion of the orchard where damage occurs, specifically the borders, that can provide a clue as to whether insects have caused the problem or it is the result of a physiological disorder.

Monitoring for stink bugs presents several problems. Because the insects occur on native plants outside of the orchard, it is helpful to sample in these areas to determine the stages present and to gather data on relative abundance from year to year. Near the orchard border, inspect mullein at the base and between the leaves to determine stink bug presence. A beating tray can be used to sample bitterbrush along orchard perimeters previously associated with stink bug damage. Samples taken every three weeks throughout the season will help in monitoring stink bug development. A beating tray is not a good monitoring method to use in the orchard later in the growing season. Visual inspection of trees along the border will better determine potential for damage. Inspect 50 fruit per tree from trees in the outside row; if any stink bugs are found the potential for injury exists.

High levels of fruit injury can occur on orchard borders adjacent to native habitats. Fruit injury as high as nearly 50 percent has been observed on border trees in some orchards near Chelan. In these orchards fruit injury was also found to be three to four times greater in the upper part of the tree compared with that at mid-canopy. This pattern of fruit injury strongly suggests that well-timed border sprays could prevent most damage along threatened borders.

Laboratory studies conducted on field-aged pesticide residues indicated that seven-day-old residues of Carzol 92 SP (formetanate) and Thiodan 50 WP (endosulfan) killed 100% of the consperse and conchuela stink bug adults. Asana 0.66 EC (esfenvalerate) was active as a one-day-old residue against both stink bug species but was not very active as a seven-day-old residue. Guthion (azinphos-methyl) and Lorsban (chlorpyrifos) were not effective against either stink bug species as one-day or seven-day-old residues.

In North Central Washington passive monitoring methods and potential biological control agents of stink bugs are currently being investigated. Six prototype trap designs baited with a stink bug attractant are being evaluated this summer in areas historically associated with high stink bug pressure. A successful trap design will greatly reduce the time and labor required to monitor for these pests. Natural enemies of stink bugs, primarily small egg parasitic wasps, occur in Washington. Studies indicate these wasps may have potential in controlling stink bugs in orchards practicing soft pest management programs.

Stink bugs are occasional but serious pests of pome fruits. A better understanding of this pest will help us to manage its populations and reduce fruit damage.


CAMP Site Update, Summer 1997

Lake Osoyoos: Within the original 400 acres of this project, codling moth catch in pheromone traps is well below that of a year earlier; first generation catch averaged only 0.1 per trap, versus 0.8 in 1996. Sterile CM from the Osoyoos, BC, facility have been released twice weekly since the beginning of flight in May. Close to 700/acre/week are being released on 480 acres. Sterile moth release last year did not begin until just prior to second generation flight. Almost all growers this year in the original acreage have elected to apply no covers for codling moth control, in contrast to nearly two per acre on average last year. The new acreage added to the project this year, bordering the original project on the south, has mostly received a full rate of 400 Isomate-C+/acre, with a few blocks being treated with 300/acre, and has had at least two covers for first generation codling moth. Mid-season fruit exams have turned up almost no fruit damage from insects in any part of this CAMP site.

Progressive Flat: This first year site near Okanogan, WA, has completed the first CM generation with relatively low to moderate catch in pheromone traps. Average CM per trap for the first generation was about 1.8, with 5% of the traps accounting for almost 35% of the catch. Most growers have applied 200 Isomate-C+ dispensers per acre and, despite the generally low CM pressure, have put on 2 or 3 cover sprays, in order to further reduce CM populations. Fruit exams have turned up almost no CM damage at this point, and minimal, localized damage from campylomma, apple scab and hail. Leafrollers are also being monitored with pheromone traps. Close to 80% of those trapped have been obliquebanded leafrollers, with much smaller amounts of fruit-tree and pandemis leafrollers.

Brewster: The BAM also has relatively low CM populations, with first generation catch averaging 2.3 per trap. Most growers have applied one to two covers. Isomate-C+ rates are mostly 200 per acre, with a few at 300/acre and some borders at 400. As with all sites, CM populations tend to be concentrated in a few blocks. Here, three blocks, totaling less than 10% of the 2300 acres in the project, account for over 50% of the CM caught. The Brewster area has a history of leafrollers, and many growers have targeted their control efforts at this pest. The first flight has yielded an average of nearly 25 OBLR per trap, through July 11, with some areas catching nearly double this. The flight appears to be extended and less than expected for some growers, perhaps the result of Bt applications in the post-bloom period. Tentiform leafminer is an increased problem this year for many in this project and elsewhere, due to an apparent reduction in parasitism of the first generation, and some insecticides were applied for this pest.

Howard Flat: This project had the misfortune to receive considerable hail damage on June 21, part of an extensive area that was hit in North Central Washington that day. Pest-wise, problems are few in this project. First generation CM catch in this third year of the Howard Flat project is very low, averaging but 0.2 moths per trap, versus 1.3 (1996) and 7.4 (1995) for the same area. Isomate-C+ rates have dropped on average to below 300 per acre, and most growers have applied only one cover spray or less for CM. The Chelan River addition to this project also received hail to much of the area. CM counts here are higher than Howard Flat on average (5.7 per trap though July 8), and many growers have applied two or more covers. On the largest orchard in Chelan River, mating disruption has been used for two or more years in most of the acreage, and CM counts average only 1.5/trap. The first leafroller flight is continuing at these sites. OBLR is the dominant species, in contrast to last year when PLR was the most common.

Manson: This site along Lake Chelan has close to 1100 acres being monitored for CM and leafrollers. There is also extensive acreage in the Manson area outside this CAMP site using CM mating disruption this year, much of it for the first time. CM populations are moderate for many growers here. First generation catch for participating growers averaged 5.7 per trap, through early July. Counts for adjacent non-participants have averaged 20.6/trap. Most growers have applied Isomate-C+ at 200 dispensers per acre and put on two or more cover sprays. Fruit exams have turned up negligible amounts of CM stings or entries. Leafrollers are being monitored with pheromone traps and populations of both PLR and OBLR appear to be very low.

West Parker Heights: This third-year CAMP site is using Isomate-C+ at 400/acre to all of the acreage except for 12 acres with Checkmate-CM, and another 40 acres treated with an Isomate dispenser containing both codling moth and leafroller pheromone (the "dual" dispenser). The CM catch (1.4/trap on average) is a further 20% below that of last year, and extensive fruit exams have turned up no fruit damage. Most growers applied one cover for the first generation. Pandemis leafroller has been a concern for some growers at this site, and most made several Bt applications following bloom. PLR catch in pheromone traps to date is similar to last year. Other secondary pests are not generally a problem at this time, although there have been a few more hot spots of rosy apple aphid than in past years, and white apple leafhopper numbers may be high in some orchards with the next generation.

West Wapato: Growers within this site have CM mating disruption on close to 800 acres. Both the Isomate and Checkmate dispensers are being used, with Isomate-C+ rates ranging from 200 to 400 per acre. All growers have applied two covers for the first generation. CM catch in pheromone traps has revealed a wide range in CM levels across this project, with some traps catching well above 100 moths for the first generation, and many others with only zeroes. The combined approach of cover sprays with mating disruption should serve to greatly reduce the high CM numbers. Fruit exams have turned up only a few areas with CM damage. Pandemis leafroller catch in traps is quite high in areas (>250 PLR/trap), and many growers will be targeting summer generation larvae with Bt sprays.

Carpenter Hill (Medford): Mid-season fruit exams at this 500-acre site have turned up no damage to pears or apples from CM. Growers here have relied upon a program of three horticultural oil applications, together with 400 Isomate-C+ per acre, for control of CM. CM populations, as measured by catch in traps, appear to be similar to 1996 levels (2.8/trap through June). Fruit damage from true bugs (lygus and others) continues to be a problem in some areas, as was the case last year. Control of these pests can be difficult where broad spectrum insecticide use is minimized or eliminated, as in this selective program developed in Medford. They are investigating vegetation management as a means to reduce the problem.

Mendocino: As pear harvest approached at this new CAMP site near Ukiah, CA, growers showed large reductions in both CM populations and sprays for their control. Overall CM catches in traps are down 75% from 1996, when mating disruption was first used here. CM fruit damage is at barely detectable levels. Cover sprays are down 65% on average from last year, with this year nearly 75% of the acreage receiving no covers. Total organophosphate use appears to be down over 80% from 1995, the year prior to mating disruption use. Most secondary pests, including leafrollers, psylla and spider mites, are under control, although there has been some damage from boxelder bugs to orchard borders along the Russian River.

Randall Island: By mid-July, harvest was complete for most of the orchards within this project, and, in general, the year held few surprises. Growers who used a single application of Isomate-C+ at 400 per acre, together with a single application of either Guthion or Penncap-M at the second peak of the overwintering CM generation, kept CM fruit damage levels below 0.1%, and leafroller damage below 0.2%. Growers who reduced OP use still further had mixed results, some having unacceptable levels of damage. The acreage that had used no OP’s for over three years, relying solely on mating disruption for codling moth control, required two OP applications this year to suppress CM adequately. Dr. Stephen Welter, who has worked with the growers at this site since mating disruption was introduced here in 1993, believes that in California pears a single OP application will be needed most years to supplement the control provided by mating disruption. With that approach, cover sprays for CM will be reduced about 75% compared with conventional programs there. Leafroller populations have increased overall within Randall Island since the project began in 1993, and the potential for leafroller outbreaks must now be considered each year.

A Call for New CAMP Site Proposals

The USDA-Agricultural Research Service will again be providing funding to support the establishment of areawide control sites using mating disruption as the key part of a codling moth management program. In 1998, five or six sites will receive up to $40,000 for one year, to be used to hire people for the monitoring and coordination of the site, and to purchase pheromone traps and lures and other monitoring supplies.

To qualify, proposed sites must:
  1. contain at least 400 acres of apples and/or pears
  2. involve at least five growers
  3. have reasonably contiguous bearing acreage

In addition, sites will be favored that have a strong likelihood of continuing the areawide control approach for more than the one year for which funding is provided by the USDA-ARS. Sites will also be preferred from areas where experience with mating disruption for codling moth control is limited and where mostly small to mid-sized growers are involved (less than 100 acres each).

Proposals need to be received by September 30 at the USDA-ARS Lab near Wapato, WA. Address to:
Dr. Carrol Calkins, Yakima Agricultural Research Lab 5230 Konnowac Pass Road Wapato, WA 98951

For more information, call Dr. Calkins at (509) 454-6570, or Ted Alway, WSU Cooperative Extension, Wenatchee, (509) 664-5540.


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

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.

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

Wenatchee WA, 29 July 1997