WSU Tree Fruit Research & Extension Center

Pear Entomology

Friday, March 22, 2019


Areawide Organic Background

There are approximately 26,000 acres of pears grown in eastern Washington, the state's second largest tree fruit commodity (WASS 2000). Pear growers spend between $12 and $18 million annually on insect pest control, primarily for control of pear psylla, codling moth, tortricid leafrollers, phytophagous mites and grape mealybug (WASS 2000). Increasing costs associated with pest control have made pear production less economical in recent years, particularly with decreasing crop prices. While the use of integrated pest management practices has increased substantially over the past twenty years, significant challenges remain, including reduced crop prices, increased chemical costs, limited tactics for pest management, and increased amounts of pesticides necessary to maintain economically-low pest damage.

Present pest control programs for pears are largely based on chemical sprays that destroy beneficial as well as pest arthropods within the orchard agroecosystem (Dunley et al. in press). At best, these programs have offered temporary protection while producing many unwanted side effects (Dunley et al. in press). Control programs based solely on chemical tactics are less desirable because of real or potential human hazards (both at the time of application and as food residues), environmental contamination, and increased production costs borne by producers and consumers. Chemical control programs also require high inputs of fossil fuel-derived materials and other non-sustainable supplies. For these reasons it is necessary to examine alternatives to existing pear pest management programs. Non-chemical pest control, using biological, semiochemical, autocidal, or cultural tactics, presents the best alternative to the traditional chemically-intensive programs. Biological control is the optimal sustainable approach.

However, biological control alone cannot currently control any of the major arthropod pests of pear. Thus, to obtain a long-term stable pest management program in pears, research is necessary to develop a consistently effective integrated program that coordinates chemical control with biological control, and also uses semiochemical and cultural control practices. A small percentage of Washington pear growers (approx. 5%) have already chosen to become organically-certified, using pest management programs that that rely solely on these more biologically-intensive pest management strategies and tactics. The number of organic fruit growers in Washington has risen dramatically since 1995, largely due to the success of mating disruption for control of codling moth, the key pest of apple and pear. Control of codling moth without organophosphate insecticides, prior to the development of codling moth mating disruption, was very difficult and costly, and served as a major barrier to development of more environmentally-benign IPM programs.

The first areawide use of mating disruption for codling moth control began in the Sacramento Delta of California in 1993. Called the Randall Island Project, this project was directed at managing organophosphate resistance in codling moth, primarily through reducing azinphosmethyl (Guthion) use by augmenting codling moth control with mating disruption. In 1995, a cooperative project between Washington State University, University of California-Berkeley, Oregon State University, and USDA-ARS established codling moth areawide management projects (CAMP) in Washington, Oregon, and California. The primary objective of the CAMP projects was, like the original Randall Island Project, to reduce organophosphate applications using mating disruption (Brunner et al 2001). These projects ran through 1999, during which use of mating disruption for codling moth control in Washington apple increased from less than 5% of the acreage to a peak of about 55% of the acreage in 1999. Overall, the CAMP projects have been viewed as highly successful in promoting and improving IPM programs in apple and pear throughout the US (Brunner et al 2001).

Another project, 'Areawide II,' was initiated in 2001. It involves the same cooperators as CAMP, and is funded by the USDA IFAFS and RAMP programs. The objective of this project is to extend the benefits of mating disruption, primarily by developing softer IPM programs that enhance biological control in tree fruit. This program is in progress, seeking to further reduce use of organophosphates and develop programs that encourage the use of natural enemies. Target pests include pear psylla and leafrollers, in addition to codling moth.

While the CAMP and Areawide II projects broaden IPM research, relatively little has been done toward further developing organic tree fruit production. The successful development of codling moth mating disruption has finally given organic fruit growers a viable means of controlling this pest, as prior botanical insecticides and pathogens made control very difficult. Other IPM techniques investigated in the Areawide projects, such as monitoring and augmentation of biocontrol agents, have also helped organic growers better control their insect pests. The increasing availability of organic pest control options, as well as a price premium for fruit, has led to increasing acreage under organic production over the past several years.
However, the potential for areawide implementation of organic production has not been examined. Organic pear production may particularly be appropriate for areawide implementation. The major pests of pear, codling moth and pear psylla, have biological traits and available pest management tactics that should be amenable to areawide organic management. Successful areawide management of codling moth has already been demonstrated; areawide management of pear psylla has also been demonstrated, but in a less formal setting.

In the mid-1980's, pyrethroids were used in an areawide program for pear psylla control in the Wenatchee Valley of Washington (Burts et al 1984). Unfortunately, this areawide control program was implemented without proper consideration of resistance management. While this regional control program was successful for several years, it also led to regional development of pyrethroid resistance. The insect growth regulator fenoxycarb (Comply) was subsequently used successfully in an areawide program for five years in the mid-1990's. However, fenoxycarb did not receive EPA registration and the use of this tactic ceased. Currently, areawide management of pear psylla is being attempted in the same region using Surround, a kaolin-based particle film technology.

Two characteristics make pear psylla appropriate for areawide management. First, it is host specific; infestations from populations on alternate or wild hosts are not a concern. Secondly, pear psylla is very dispersive, particularly in the overwintering stage. Although psylla density in one orchard may be lower than in others at harvest, regional population mixing regularly brings densities back to the regional mean by the following spring (Westigard et al. 1979). Alternatively, when regional pesticide applications were successful in reducing psylla densities throughout an area, pear orchards with historically poor psylla control and higher psylla densities benefited from areawide management, resulting in lower densities without increasing control in those specific orchards.

There are some additional benefits to implementing organic production on an areawide basis, rather than orchard by orchard. Foremost is enhancing the opportunities for immigration of natural enemies. Most natural enemies of pear psylla are opportunists, and immigrate from native surrounding vegetation into pear orchards. For this to occur, the pear orchards must be adjacent to native vegetation, typically along the margins of production areas. Establishment of organic orchards in the middle of conventional production areas will have more difficulty encouraging biocontrol agents, as less selective pest management programs in the conventional orchards will likely isolate the organic orchards from the native vegetation. Areawide implementation of 'softer' organic production will provide 'corridors' for biocontrol agents to immigrate to the interior of production areas.

Description of anticipated risk reduction
We expect to greatly reduce the use of conventional pesticides for management of insect pests, decreasing risk to workers and the environment. Broad-spectrum neurotoxins will be avoided (100% reduction in organophosphate use). Pest control will primarily be accomplished using biological control, with augmentation using kaolin clay (Surround), Bts, mating disruption, and the botanical insecticide azadirachtin (Neemix, Ecozin, AzaDirect). Insect growth regulators (pyriproxifen, diflubenzuron, methoxyfenozide) will be used if further insecticide interventions are necessary.

Records will be maintained of all insecticide inputs. Comparisons of insecticide inputs will be made with conventional orchards within the region, as well as inputs from orchards within the project from the previous year. Additionally, biweekly samples of pest and natural enemy densities will be taken by WSU personnel. Changes in numbers of applications, insecticide selectivity, and natural enemy populations will be calculated, and comparisons made with conventional orchards. Overall costs of insect control programs will be calculated, and will be compared with previous years' costs as well as costs from conventional orchards.

References cited
Brunner, J. F., S. Welter, C. Calkins, R. Hilton, E. H. Beers, J. E. Dunley, T. Unruh, A. Knight, R. Van Steenwyk, and P. VanBuskirk. 2001. Mating disruption of codling moth: a perspective from the Western United States, pp. 207-215. Use of pheromones and other semiochemical in integrated control, Samos, Greece. OPBC WPRS.
Burts, E. C. and A. H. Retan. 1984. Pear psylla detection and control. Wash. State Univ Ext. Bull. 1230. 4 pp.
Dunley, J. E., E. H. Beers, and J. F. Brunner. In press. On-farm implementation of an acaricide resistance management strategy on pear on Northcentral Washington. J. Tree Fruit Production.
Dunley, J.E., and S.C. Welter. 2000. Correlated insecticide cross-resistance in organophosphate resistant codling moth. J. Econ. Entomol. 93: 955-962.
WASS. Washington Agricultural Statistics Service. 2000. Agricultural chemical usage, 1999 fruit crops. NASS, Washington, DC.
Westigard, P. H., P. B. Lombard and D. W. Berry. 1979. Integrated pest management of insects and mites attacking pears in southern Oregon. Sta. Bull. 634. Agric. Exp. Sta., Oregon State Univ.

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