|Vol. 3, No. 9||September 1, 1998|
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.
To apply a pheromone with a conventional sprayer it must first be microencapsulated. Microencapsulation was first developed in the late 1950's, and is a part of such technology as NCR (no carbon required) paper, scratch and sniff products, pharmaceuticals, flavoring additives and more. Pheromones were first microencapsulated in the 1970's. A number of insecticides have also been microencapsulated to both extend their life and increase safety to applicators and non-target organisms. The microencapsulation process involves mixing the core material (pheromone) with a polymer and then, through a number of carefully controlled steps, producing the microcapsules. Capsule diameters of from 1 to 1000 microns can be produced. Close to 20 microns (about half the diameter of a human hair) is the average size currently selected for encapsulating most pheromones.
Microencapsulated pheromones are released from within the capsule by diffusing through pores in the capsule wall. This creates a controlled time-release product. The capsule wall also protects the environmentally sensitive pheromone inside from the effects of oxidation and UV light. As the pheromone is released the capsule collapses, eventually degrading into inert substances. The 3M Corporation of Minnesota and Ontario, Canada is the leading producer of microencapsulated products, including pheromones.
Sprayable pheromones have advantages when compared with the use of hand applied dispensers. Sprayable pheromone, because of the relative ease and speed of application, can be applied in response to the detection of pest problems, instead of prophylactically, as with hand applied dispensers. For example, a pheromone spray can be applied for a flight of leafrollers or leafminers if larval counts in the previous generation indicated the need. Sprayable pheromones can be applied with other materials in the spray tank, saving or sharing the application cost. In addition, the amount of expensive pheromone applied per acre in one or several sprays may be less than the amount per acre found in dispensers, potentially providing further cost savings. For example, the recommended rate of the leafroller MEC product is 20 grams of pheromone per acre; at the recommended application rate for the Isomate CM/LR dispenser there is close to 50 grams of leafroller pheromone per acre.
Currently, the main drawback with microencapsulated pheromones is their longevity, compared to hand-applied technologies. Small capsules allow for easy suspension and spraying and good distribution within the canopy, but they also have a high ratio of surface area to volume. This usually results in the pheromone being fully released within a few short weeks, as a first order release rate. The size of the capsule and the wall thickness and composition can be adjusted to vary the release rate, within limits. Current sprayable formulations last 2 to 4 weeks, depending upon temperatures. The manufacturers hope, by improvements in microencapsulation, to extend this period to 6 weeks or more.
The effectiveness of a sprayable pheromone for mating disruption depends upon several factors. A key one is the sensitivity of the target insect to its own pheromone. For example, the greater peachtree borer appears to be highly sensitive, with one application of a small amount of pheromone (10 grams/ac) sufficient for the entire season. In contrast, leafroller flight and mating is never fully shut down, even with excessive pheromone rates. Larvicides, such as Bt or spinosad, will be needed to supplement control
Sprayable pheromone products have been developed for a number of crop pests, including pink bollworm, tomato pinworm, grape berry moth, blackheaded fireworm (a cranberry pest) and, for tree fruits, peachtree borer, oriental fruit moth, peach twig borer and obliquebanded/pandemis leafrollers. Producers of sprayable pheromone products for fruit crops include 3M, Scentry Biologicals (Billings, MT), Consep (Bend, OR), and Ecogen (Langhorne, PA).
The first registration of a sprayable pheromone product for Washington tree fruits was for leafrollers in 1997 with Ecogen's NoMate LRX. 3M has registered a MEC leafroller product that will be commercially available in 1999. Both products have been tested extensively in Washington. The MEC product, containing one component of the leafroller pheromone (Z11-14 Ac) is used for both pandemis and obliquebanded leafrollers. Applications of 20 grams/ac of pheromone have shut down leafroller catch in pheromone traps for about a 2 week period. This treatment appears to provide less suppression of catch in traps than the hand-applied dispensers that are available. Doubling the rate to 40 grams/ac only provides a small increase in the trap shut down period. However, reduced catch in traps is not necessarily an indicator of mating disruption and critical research questions remain. The best fit for this product at this time is probably as a management tool to help suppress leafroller populations and should be used in conjunction with other controls, such as sprays of Bt and spinosad. Whether the suppression is adequate will depend largely on the material cost.
The manufacture of sprayable pheromones is undergoing continual development and improvement. This should result in formulations with greater residual life and efficacy, as well as sprayable pheromones for an increasingly wide array of crop pests. By next year apple producers could see testing of a sprayable product for leafminers, and sprayables for other fruit pests should soon be on the scene. As with any pest management product, the extent to which they are used will depend upon how effective they are and how they are priced. With the many changes that are occurring in orchard pest management programs, sprayable pheromones for several pests will find their niche in the coming years.
Life History and Damage
The apple maggot overwinters in the soil as a pupa. Flies emerge over an extended period, beginning in late June or early July and extending into September. They are about the size of a house fly, with distinctive black bands on the wings. After emerging, the fly feeds for 7 to 10 days before it is sexually mature and mating can take place. Female flies then lay eggs just under the skin of the fruit. Each female has the potential to produce between 300 and 500 eggs. The resulting larvae tunnel throughout the fruit, leaving brown trails in the flesh. From the outside, damage is visible as a lumpy appearance to the fruit, with small punctures surrounded by darkened cells. Breakdown and rot of the fruit usually follow larval feeding. After feeding for 2 to 6 weeks or more the larvae leave the fruit and pupate in the soil. There is one generation per year.
Apples, crab apples and hawthorns are the preferred hosts in Washington. AM have become established in native hawthorns in the West, their original host in the eastern US as well. Without control, AM can damage almost all the fruit on infested apple trees. Typical control treatments for eastern apple growers involve the application of broad spectrum insecticides, such as Imidan or Guthion, at regular intervals from soon after the first flies are caught in traps, typically in July, until close to harvest. There are several wasps that attack AM and they provide some control in hawthorns; unfortunately, these parasitoids are ineffective in the larger fruits of apples.
Apple Maggot in Washington
AM has been found in several western states within the past few decades, including California, Oregon, Idaho and Washington. These finds are probably the result of infested fruit being brought into the area from eastern states. The first confirmed find of AM in Washington was in Vancouver, WA in 1980, although it probably was in the area before then. The Washington State Department of Agriculture began an extensive trapping program the following year and soon turned up populations in the Columbia River gorge and the Spokane area. WSDA control/containment programs were initiated soon after but were abandoned by 1985 as it became clear that AM had become established in the native hawthorns of these areas and that the funds available for the program were limited. Despite this, AM infestations in eastern Washington are still restricted to these two areas, although there has been some further spread in western Washington.
An AM quarantine program was begun in 1984 to limit the spread of this pest. Eighteen counties are involved, most of these in southwestern Washington. In 1998, Skagit County was added to the quarantine list, becoming the first county with significant commercial apple production to be quarantined. Flies were found in 18 locations in the county in 1997, mostly near Mount Vernon with some additional finds near Sedro Wooley and Anacortes. The movement of non-commercially produced apples out of quarantined counties is prohibited in this program. Commercial fruit can only be moved out of the county if trapping within half a mile of the orchard turns up no apple maggot flies and/or fruit inspections by the WSDA show the fruit to be free of larvae. For information on the WSDA permit or certification process and the statewide AM survey contact Mike Klaus, Entomologist, WSDA, at (509) 454-4189.
In Yakima an AM fly was found in 1995 in a residential area apple tree. In 1996, five locations in Yakima County caught single flies, none of them in commercial orchards. Trapping was expanded in 1997 and only one fly was found, in a new location. In 1998, intensive trapping continues in Yakima, Benton and Kittitas Counties, with 3,654 traps deployed in Yakima alone. In 1997, flies were also caught for the first time in Benton County (near Kennewick) and in Kittitas County (near Ellensburg); again none were in commercial orchards. Following a find, the trees in the vicinity are either sprayed the rest of the year with an insecticide (most commonly Imidan) or have all their fruit removed. Mike Klaus of the WSDA is working closely with the Pest and Disease Control Boards in each of the counties where flies have been found to eradicate them and prevent any threat to commercial orchards in the area.
In 1998 there are more than 5,600 AM traps deployed throughout Washington, concentrated most heavily in the regions where flies were found the previous year. More will be installed in the vicinity of any finds that occur. As of late August, there have been no flies trapped in central Washington, despite the early season and hot summer temperatures. Insecticides are being applied where flies were found last year. Hopefully, this is an indication that AM are at extremely low levels or non-existent. AM flies have been found in the Spokane Valley area where it has been known to occur since the 1980's. Catches so far in Skagit County have been only in residential areas.
The implementation of the Food Quality Protection Act will probably result in significant use restrictions and losses of most of the organophosphate and carbamate insecticides presently used in Washington orchards. New, more specific control methods, like insect growth regulators and mating disruption, are being incorporated into pest management programs by Washington growers. The "softer" programs that result can provide more opportunities for biological control of some orchard pests. They can also, however, provide openings for other, less common pests to become better established in certain areas, among them lesser appleworm, oriental fruit moth and AM.
AM is the most serious of the potential pests, as the larvae must feed directly on the fruit. Established populations of AM can require regular applications of insecticides from July into September, at a time when insecticide applications are done for most Washington growers. It is unclear what if any effective insecticides will be available for AM control if organophosphates and carbamates are not registered for summer use. In addition to the added expense to growers of these sprays there is also the risk that insecticides applied at this time may disrupt the integrated pest management systems used in orchards, including biological control of mites, leafminers and aphids. Washington growers export of much of their apple crop each year, which is very important to their bottom line. Should AM become established in commercial orchards, many export markets could be closed to apples from these areas, causing further economic losses. For these reasons, the monitoring, containment and local eradication of apple maggot in Washington must be ongoing and successful. Stay tuned.
To qualify, proposed sites must:
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 no later than September 30 at the USDA-ARS Lab near Wapato, WA. We would like to arrange a site visit prior to then; please contact Dr. Calkins or Ted Alway if you intend to submit a proposal. Address proposals to:
For more information, call Dr. Calkins at (509) 454-6570, or Ted Alway, WSU Cooperative Extension, Wenatchee, (509) 664-5540.
Ted Alway, Editor
Phone: (509) 664-5540
Fax: (509) 664-5561
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
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