April 1, 2002
Vol. 4 No. 2
Codling Moth Mating Disruption Revisited in 2002
Codling moth mating disruption (CMMD) was first commercially available in Washington in 1991. From just a few thousand treated acres in 1992, its use climbed to close to 90,000 acres in the state by 2001. Growers have adopted this new pest control method because it made economic sense. Faced with increasing codling moth (CM) pressure and control costs, they were able to incorporate CMMD into their pest management programs and reduce both pest control costs and codling moth damage.
This past year has seen increasing concern with CM in the Northwest. Reports of high fruit damage are becoming more common. Several factors are contributing to this growing problem:
Due to several years of low economic returns for fruit, some growers have cut back on control expenditures, using reduced numbers or rates of cover sprays, and reducing CMMD dispenser rates or eliminating use of dispensers altogether
The number of abandoned or poorly managed orchards has increased, resulting in higher than normal CM infestations and increases in local and regional CM populations
Some growers use little or no monitoring for CM and are therefore unaware of where they have problems developing and are unable to respond in a timely fashion
The organophosphate (OP) sprays used as cover sprays are not as effective for CM control as they were in years past
Due to increasing CM populations and economic issues facing Washington growers the use of CMMD is being called into question by some in the industry. Does it make sense to continue with CMMD use? I think it still does for most Northwest growers, for the same reasons and with the same qualifiers as before.
CMMD can reduce sprays - there are many examples in Washington over the past ten years where the use of CMMD has reduced CM cover sprays from 3, 4 or more per acre per year to an average of 1-2 sprays or less. This was demonstrated repeatedly in the CAMP (Codling Moth Areawide Management Program) sites from 1995 to 1999. Many growers have averaged no more then one complete CM cover spray for many years. Few, if any, growers are able to eliminate supplemental cover sprays entirely, year after year. Most continue to rely upon sprays to orchard borders and hot spots, with a complete cover sprays to the orchard each year or so.
CMMD can reduce damage - persistent CM populations, causing 1.0% fruit damage or more despite multiple cover sprays, have been well controlled when CMMD was combined with cover sprays.
CMMD can save money - most growers are successfully using 200-250 CMMD dispensers per acre. Eliminating more than two cover sprays will generally by itself make up for the cost of dispensers and their application. Likewise, CM fruit damage costs the grower, and packer, money; the more valuable the fruit, the more costly the damage.
CMMD can reduce worker safety and management concerns - the use of OP insecticides, particularly azinphosmethyl (Guthion, Azinphos), poses problems with worker reentry intervals, posting fields and more; OP use can be reduced or eliminated when CMMD is part of the program.
CMMD is an important supplement to the newer, more selective insecticides - new CM control products are now available, including insect growth regulators, (Esteem and Intrepid) and the soon-to-be-registered chloronicotinyl, Assail (more on these new materials in an upcoming issue of this newsletter). Although effective, none provide control equal to the OP insecticides. With the probable cancellation of azinphosmethyl and phosmet (Imidan) use within four years, these and other more selective and less robust insecticides will be crucial to CM control. The successful use of these new insecticides will in large part depend on incorporating them into a CMMD program. Organic apple and pear producers, with far weaker CM spray options, rely heavily on CMMD, usually at full label rates of dispensers.
CMMD can permit increased biological control - natural enemies can provide partial or complete control of many pests, including leafrollers, leafminers, leafhoppers, aphids, pear psylla, grape mealybug and more, when insecticides are used that do not kill them off. CMMD can reduce or eliminate use of disruptive OP insecticide sprays, thus conserving more natural enemy activity in orchards.
CMMD has not had resistance develop to it - there has never been any documented resistance of CM to mating disruption. While is seems unlikely for CM to develop resistance to mating disruption research underway to investigate this possibility in Washington.
CMMD is not appropriate for all orchards and growers. CMMD use is a questionable IPM practice in several situations:
High external CM pressure - if there is a high CM population adjacent to the orchard, mated females can migrate in and lay eggs. In these situations multiple border or even complete cover sprays would be needed regardless of CMMD use, and the grower may decide to not use CMMD, at least in the affected area.
Very low CM pressure - if one or no cover sprays are needed to control CM the grower may be money ahead to not use CMMD. However, CMMD use can effectively slow any population buildup, keeping the need for future cover sprays very low.
Too challenging a site - orchard sites that are narrow, small or steep may have trouble maintaining enough pheromone in the orchard for effective CMMD. However, these kinds of sites can be effectively incorporated into an areawide program by cooperating with other growers in the region.
When CMMD is used, keep in mind several key considerations that are critical to success:
Apply at the right time - dispensers must be in place in the orchard before CM flight occurs. The moths mate soon after the first male flight, which occurs close to full bloom of Red Delicious. In any CM management program it is crucial to achieve good control of the first generation. Applying mating disruption dispensers late increases the amount of mating, egg laying and fruit infestation that can occur, and increases the need for further controls aimed at the second generation. It is far better to apply the dispensers two to three weeks before the beginning of the flight than even one week late. Good CMMD dispensers are available that will last all season under Washington's environmentalconditions (see below), and a very small proportion of the total amount of pheromone is emitted before bloom.
Apply high in the tree - dispensers must be placed in the top two feet of the canopy, at or above the level of any fruit. Codling moth activity and mating are concentrated in the top third of the canopy and, since pheromone is heavier than air, it tends to sink towards the orchard floor as it is released. Supervise the application of dispensers to ensure the proper height is maintained, particularly later in the day when arms get tired and trees seem to get taller!
Apply uniformly - hand-applied CMMD dispensers must be placed uniformly throughout the treated orchard so that there are few holes in the pheromone "cloud". Use a regular and consistent pattern for dispenser spacing to get the desired number per acre. If a tree is missing, place its dispensers in the surrounding trees. Likewise, if there are small interplants in the block, place the dispensers that these trees would have received in the surrounding taller trees, so that dispensers are not just six feet or less from the ground. In situations where external populations of CM exist is might be wise to double the dispenser rate on border rows but this should not take the place of uniform applications throughout the remainder of the orchard.
Monitor the orchard - use of appropriate lures and traps to monitor the CM and help determine the need for and timing of sprays is a must in implementing a successful CMMD program. Monitoring CM with pheromone lures in traps in a mating disrupted orchard is less reliable than in a non-disrupted orchard. Near the end of the first generation (mid June to early July in most Washington sites) orchard borders should be examined for fruit damage. (More on monitoring in the next issue)
Supplement with sprays as needed - most orchards will need a supplemental CM cover spray in addition to CMMD each year, even if only to a portion of the block. CMMD can greatly reduce the need for cover sprays, but will rarely eliminate them completely.
Hand-applied Dispensers for CMMD
Almost all CMMD in Washington is conducted with the use of one of several commercially available hand-applied dispensers. Sprayable pheromone and "puffers" (mechanical pheromone dispensers) are also now available. They continue to be refined and have been little used commercially to this point. However, these pheromone delivery methods potentially provide some significant advantages; I'll cover their use in a later issue.
Five dispensers were evaluated in 2001 by the WSU-Tree Fruit Research and Extension Center in Wenatchee (TFREC). They were checked for the duration and rate of release of the primary CM pheromone component, codlemone. Dispensers were clipped onto a line that ran through the canopy of an apple orchard at the TFREC. All dispensers are designed by their manufacturer to be applied just once per season in Washington conditions.
||Labeled codlemone load (mg)
|Checkmate CM XL-1000
All dispensers were evaluated by two methods:
- Volatile Trapping System (VTS) Method - Dispensers were collected at approximately 30-day intervals and analyzed in the VTS by Phero Tech of British Columbia. Filtered (clean) air of a constant temperature and flow-rate was run over the dispensers and the codlemone emitted from dispensers was trapped on a special column and measured using a gas chromatograph.
- Residual Analysis Method - Dispensers were collected at the same intervals and analyzed by the WSU Food and Environmental Quality Lab in Richland. All of the pheromone in each dispenser was removed and the amount determined, again using a gas chromatograph.
The VTS method provides a relative comparison of the amount of codlemone released per dispenser type of different ages under constant environmental conditions.
||Calculated mg of codlemone released per dispenser over 24 hours
What the ideal dispenser would do is release an adequate amount of codlemone for the entire season, that is independent of age. After an initial "burst" affect on day-0, most dispensers had a fairly constant rate of pheromone release. However, there was great deal of difference in the amount of pheromone released by each dispenser type. The Isomate-C plus and CTT dispensers had the highest and most consistent release rates. The Checkmate and Disrupt CM dispensers had consistent but very low release rates. Pheromone release from these latter dispensers could have been inhibited by the way they were arranged in the VTS. Three dispensers of each type were placed in the VTS chamber. It is possible, though Phero Tech does not think it was the case, that air flow was impeded over the Checkmate and Disrupt dispensers thus reducing their pheromone release rate. The NoMate dispenser is an unusual case. The dispenser showed a very high initial pheromone release rate and appeared to run out of pheromone later in the season. See the discussion below for a further explanation of this situation.
The residual analysis method determines the amount of codlemone remaining in dispensers of different ages; the difference in the amount remaining in the dispenser at each time period is a measure of the amount released.
||Average amount (mg) of codlemone remaining per dispenser
|Age of dispenser (days)
||Isomate C plus
Most dispensers showed a gradual decline in the amount of codlemone remaining over time. Both Isomate dispensers showed a similar pattern in the amount of codlemone remaining, though by design the CTT dispenser lost about twice as much pheromone as the Isomate-C plus dispenser. The pattern of codlemone remaining in the NoMate was similar to that observed from the VTS analysis. Less than 50% remained in the NoMate dispenser after 35 days and by the end of the first codling moth generation (ca. 84 days) little codlemone remained. The Checkmate dispenser lost codlemone throughout both generations but still had nearly 40% remaining after 162 days. The Disrupt dispenser was the least consistent in codlemone loss, especially in the second generation, and had almost 50% remaining at day 162.
Both methods of analysis showed similar results, and residual analysis showed little isomerized pheromone in any of the dispensers suggesting all were protecting the codlemone from internal breakdown. Both methods of analysis appear to provide an adequate means for measuring pheromone release behavior from hand-applied dispensers and this research will continue in 2002
Rick Hilton of the OSU-Southern Oregon Research and Extension Center evaluated these same dispensers in Medford. Using the residual analysis method, he obtained results that closely matched those found in Wenatchee. The Isomate and Checkmate dispensers continued to lose pheromone for 120-150 days, while the NoMate dispenser was essentially out of pheromone by 90 days.
The manufacturer of NoMate (Scentry Biologicals Inc.) is concerned that the dispensers used in these tests were somehow inappropriately exposed to high temperatures prior to their placement in the orchard. This would cause pheromone in the NoMate dispensers to migrate to the surface and therefore be lost at a faster rate than the dispenser's design should permit. While the dispensers used in the Wenatchee and Medford study were current year NoMate dispensers (red) and were removed from a newly opened package it is possible they were exposed to improper storage conditions prior to use. Improper storage could have affected any of the pheromone dispensers in a similar manner pointing out the importance of proper storage for distributors and growers. In 2002 WSU will again evaluate all hand-applied CM pheromone dispensers but will evaluate all dispensers prior to placing them in the field to make sure they meet label standards.
For a complete report of the 2001 hand-applied pheromone dispenser analysis go to the web-site at http://entomology.tfrec.wsu.edu/stableipm/workshop.html
Ted Alway, Coordinator Areawide II
Phone: 509-663-8181 x268
In this issue...
Codling Moth Mating Disruption Revisited