Washington State University Cooperative Extension

Areawide IPM Update

The Newsletter of Pheromone-based Orchard Pest Management

Vol. 1, No. 8 -- August 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.

Puffer: A New Device for Mating Disruption

Mating disruption has become an effective control in recent years for an increasing number of crop pests, including pink bollworm in cotton, pinworm in tomatoes and oriental fruit moth in peaches. A crucial part of this success has been the means of delivering the needed amount of pheromone to the crop canopy area. Many approaches have been devised, mostly involving small dispensers that are clipped, tied, sprayed or otherwise placed within the canopy. These dispensers have taken the form of fibers, flakes, ropes, packets and more. There have been concerns with one or more of these, including the labor needed for application, uneven or inadequate pheromone output, and ultraviolet breakdown of the pheromone.

On a recent trip to California, I was able to see a demonstration of a novel pheromone dispenser, nicknamed the puffer, being developed by Dr. Harry Shorey of the University of California-Riverside. Dr. Shorey met with us at the Lake County pear orchard where he is working with Rachel Elkins, UC-Cooperative Extension Horticultural Advisor. Mating disruption for both obliquebanded leafroller and codling moth was being attempted at this site. Dr. Shorey is conducting trials with the puffer device at sites in California for a number of other pests, including peach tree borer and navel orangeworm on almonds, raisin moth and omnivorous leafroller on grapes, and beet armyworm on tomatoes.

Dr. Shorey uses an aerosol can dispenser, very similar to the devices found on the walls of public or restaurant restrooms which periodically spray fragrance into the air. Instead of being filled with Mountain Pine or Country Garden perfume, the can in this case contains an insect pheromone, such as codlemone. A small plunger atop the can, powered by batteries, depresses a valve to release a burst, or puff , of the aerosolized contents. A timer regulates the interval between puffs; 30 minutes was the interval chosen in the test we saw. The device costs about $20, and sprays at regular intervals throughout a 24-hour period. Other models are available, including ones that have timers that can limit pheromone release to specific periods during the day. For example, for codling moth the pheromone could be introduced to the orchard only prior to and during the flight period.

At the Lake County pear site, the dispensers were fixed to boards that were hung in the upper third of the tree canopy. A total of 122 were placed in this 160-acre orchard, over 100 being on the orchard perimeter. With most sites, Dr. Shorey has averaged one to two acres per dispenser, with most cans placed around the block edges. Each canister at this site contained enough pheromone to last 90 days, although each has sufficient capacity to contain an amount to last much longer for most pheromones. The dispensers here were loaded and placed to release codlemone at the rate of 150 mg/acre/day, and OBLR pheromone at 160 mg/acre/day.

Dispensers are taken down and inspected weekly. At the end of the first generation there was virtually no codling moth damage, and moth catch in 10mg pheromone traps had been largely shut down.

Several technological problems have been encountered with the puffers in the field, and most have been overcome. Finding the best propellant and blends has taken some effort, as has finding a reliable and economical dispenser. The main questions at this time concern how effective this approach will be in providing mating disruption. Further research into dispenser placement, density and release timing is needed, as well as investigation of the optimal pheromone release rates.

This approach to mating disruption potentially provides several advantages over current methods. It can release a set amount of pheromone over time, one that doesn't vary with temperature or with the age of the dispenser. This amount can be easily adjusted to suit the conditions, including pest pressure, canopy type, temperatures or time of year. Pheromone breakdown from ultraviolet light is not a concern with the sealed metal container. California growers, generally faced with higher codling moth pressure and a longer, hotter growing season than their Pacific Northwest counterparts, have had to apply the currently available pheromone dispensers at higher frequencies and rates (and higher cost) to get effective mating disruption. For these growers and others the biggest potential advantage of an effective puffer approach could be in reducing the cost of mating disruption, allowing it to be included in an effective IPM program. The puffer holds much promise; further research could lead to some big changes in mating disruption in the future.

The SIR Program: a Year of Decision

The Sterile Insect Release (SIR) Program of British Columbia has the goal of eliminating codling moth from the Okanagan, Similkameen and Creston Valleys, largely by the production and release of sterile moths. After initial high hopes and expectations, the program has encountered some difficulties and 1996 has become a year crucial to its future. Decisions made after harvest this year will determine whether the SIR Program continues, and in what form. Let s review the program s brief history and the challenges it faces.

Planning for the SIR Program began in the late 1980 s, using as a model the work of Dr. Jinks Proverbs of Agriculture Canada. In this project of the 1970 s, sterile codling moths were released in orchards of the isolated Similkameen Valley, eradicating the pest. Also eliminated was the use of insecticides for codling moth control for five years after the program ended, until codling moth reinfested the district. By eradicating codling moth, the key pest of apples in the Northwest, the SIR Program hopes that broad-spectrum insecticide use can be greatly reduced, in the process lessening disruption of secondary pests, reducing costs, and minimizing environmental concerns.

The codling moth rearing facility was completed near Osoyoos, BC, in 1993. This state-of-the-art facility was designed to rear, sterilize and release 5 million moths per week throughout the growing season. Dr. Ken Bloem was hired in June 1992 as the Program Coordinator. Funding for this ambitious project comes from both a parcel tax that all growers pay and a tax levied on property owners in the treatment area. The SIR plan divides the BC fruit growing area into two zones. The southern zone, the area currently being treated, stretches from Osoyoos to Summerland and includes Keremeos and Creston. There are 8600 acres of orchard in this zone, farmed by nearly 1200 growers. The original plan called for two intensive cleanup years in 1992 and 1993 in this area, during which wild codling moth populations would be greatly reduced by thorough control programs in the orchards and cleanup of wild and residential codling moth sources. Sterile moth releases were to begin in 1994, being concentrated in this southern Zone 1 through 1996. Meanwhile, the northern Zone 2 was to clean up their codling moth populations in 1995 and 1996, with sterile moth releases occurring in years 1997-1999.

As often happens, events have not gone entirely by the plan. In Zone 1, the cleanup in 1992-3 was not as successful as needed, leaving so many moths that it was not possible, when sterile moth releases began, to get the 40:1 sterile:wild overflooding ratio needed. Some growers did not understand that in this eradication program the amount of codling moth that could be tolerated was much less than normal and therefore a more intense spray program was required during the cleanup years. 1994 was the first release year, and glitches in the rearing and distribution of the sterile moths had to be worked out. It was found that the lab-reared moths were not as competitive with the wild moths as needed in cool spring conditions. All of this, combined with high codling moth populations, a long, hot season, low fruit prices and areas of hail, resulted in an increase in codling moth pressure that year. Any gains from the previous two cleanup years were lost.

In 1995, the SIR Program was on the ropes. Two key changes were made. A public relations effort was launched to increase public awareness, rebuild grower support and provide technical information to aid in the cleanup effort. The Provincial government stepped in with a one-time allotment of funds as an incentive for growers to aggressively manage their codling moth populations. Growers who successfully controlled codling moth that year, having no more than 0.1% damage at harvest, received a $65/acre subsidy, nearly covering the parcel tax they pay annually in support of the program. 60% of the growers did achieve this level of control, with 90% having less than 1.0% damage in their fruit. Most growers applied a five- spray Guthion program (three first-generation, two second) or a seven-spray Imidan program (four plus three). The 40:1 overflooding ratio was achieved in several districts, especially around Cawston.

1996 is now a year of decision for the SIR Program, and could be its last. The eradication program is running about two years behind the original schedule. Costs continue to creep up from the original, admittedly optimistic, budget. Some significant obstacles have yet to be addressed, including how wild source trees will be eliminated from Indian lands, and how packing-house bin movement will be controlled to prevent reinfestation of codling moth-free areas. Two key members of the SIR staff, Lance Fielding (Rearing Supervisor) and Fred Peters (Field Supervisor), have left the program this summer. Dr. Bloem is restructuring operations to address the challenges that these departures create. The SIR Board has recently hired a Special Projects Manager to help resolve some of the future funding requirements of the program. He has been asked to make recommendations to the Board in October of this year which, combined with the 1996 field results, will be used to decide the program s future.

However, as we move through the 1996 season, Dr. Bloem believes there is reason for optimism. The intensive spray program of last year, combined with sterile moth releases, appears to have greatly reduced the wild codling moth population. Peak weekly trap catch of first-generation codling moths has been less than 25% of last year s numbers, and well below historical levels. Sterile moth production is consistently at 10 million per week, much above the 5 million originally planned for the facility and making possible greater overflooding of the wild population. Growers have followed a full control program for the first brood despite low wild populations, keeping in mind that this is an eradication program. The success of first-brood control measures has been closely monitored. It appears that the 40:1 ratio will be achieved in most areas during the second half of the growing season and SIR will be used alone for second-brood control.

In collaboration with Dr. Stephanie Bloem of the USDA-ARS in Yakima, and with funding support of the Washington Tree Fruit Research Commission, SIR is testing this year the use of diapaused larvae. These are larvae that, by use of different temperature and day-length regimes in the rearing rooms, have formed overwintering hibernacula in which they can be held for months. If this procedure proves successful, it could allow for the stockpiling of codling moth during the winter when the facility was previously shut down. The moths from this treatment may also be more competitive with wild moths, especially during the cooler spring release periods.

The Sterile Insect Release Program is the only program in the world attempting to eliminate codling moth across an extensive growing area by the use of sterile moths. It is an ambitious goal with great potential benefits for all associated with the fruit industry in the BC Okanagan, if not all residents of that area. If the program survives this year, cleanup will likely begin in the northern districts (Zone 2) in 1997. We should know by the end of this year what form, if any, the SIR Program will have in the future.

CAMP Site Notes: Late July

At Randall Island the Bartlett pear harvest is nearly complete. Fruit damage from codling moth has been minimal. Functionally, it's been our best year, says Dr. Steve Welter. Only one site, that has been under mating disruption for three years and has had no supplemental OP sprays during that time, received significant CM damage, and then only along one border. Most blocks had damage levels below 0.1%. Codling moth pressure appears to be lower this year in this CAMP site and in many conventional orchards. Some growers will be applying a post-harvest OP spray to their pear blocks to limit infestation of any remaining fruits from the third codling moth brood, and thereby reduce the overwintering population. Leafrollers have not been a serious problem where OP's were applied for codling moth. Untreated areas have had more leafroller damage to fruit, at one site approaching 1.8%.

At the Carpenter Hill site, harvest of the Starkrimson pear variety will begin the first week of August, followed closely by Bartlett pears. Fruit damage assessments at the end of the first codling moth generation (late June) turned up only one CM sting in 10,000 fruit across the 400 acres. About 5% of the acreage received a Guthion spray in the first generation. Most growers are applying a Guthion in late July to protect pears as they become more susceptible prior to harvest, and to ensure low overwintering CM populations. Spider mites and pear psylla are at low levels within the CAMP site, but psylla are increasing in many nearby conventional orchards and control measures will be needed. Phil Van Buskirk and Rick Hilton report: All in all, the pest situation is a repeat of last year. Harvest-time fruit assessments will complete the story.

At the West Parker Heights site, second-brood codling moth flight has begun, with low catch within the CAMP site. First- generation trap catch averaged only 1.7 moths per trap, a greater than 50% drop from the levels of last year. More importantly, CM fruit damage was almost undetectable: 2 entries in 150,000 fruits, or only 0.001%! There are indications that this spring's weather may have contributed to lower damage by reducing CM egg production or larval survival. The need for further cover sprays is questionable, but as Brad Higbee says, "It's not over 'til it's over!" He and his crew continue to monitor other pests, finding none at levels of concern at this time. Interestingly, high levels of leafroller parasitism have been found.

The Howard Flat CAMP site is into second-generation codling moth flight; a whopping total of one moth has been caught in 448 traps over the past two weeks. Total CM catch for the first generation is down 80% from 1995 levels (1.3 cumulative average per trap in 1996 vs. 7.5 in 1995). More importantly, fruit damage samples show only 0.03% damaged. Most growers should have no need for further cover sprays this year. Three species of leafrollers have been caught in pheromone traps (pandemis, obliquebanded and fruittree leafrollers). Populations are very low or non- existent in most areas.

The Lake Osoyoos site also shows a big reduction in codling moth catch compared with last year (a 90% reduction) and also has the lowest average catch per trap of any CAMP site (0.8 moths per trap through first generation). Recently completed surveys show fruit damage from CM to be only 0.01%. Twice-weekly releases of sterile codling moths from the Sterile Insect Release facility in Osoyoos, British Columbia, began in late June. At least 700 moths per acre per week are released, and sterile moth:wild moth ratios are averaging well in excess of 40:1. After being a problem for many growers in 1995, leafrollers have been targeted by spray programs this year and populations are well down. Surveys show fruit damage of 0.07% attributed to this pest.

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, 6 August 1996