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Photo by Peter shearer, osu Figure 2 Comparison of pest control costs Average cost per acre of pesticides with high risk to natural enemies and pesticides used to control secondary pests in apple orchards. growers 1-3 used pest management programs that conserved natural enemies. growers 4-7 did not. High risk Secondary pests Researchers have analyzed pest control records from pear growers in Hood River, Oregon, as part of a project to place a value on biological control of pests. another $77 per acre for secondary pest control (Figure 2). These examples demonstrate that there are added costs associated with pest control programs that do not follow practices that conserve natural enemies in apple orchards. Growers 1-3 Pears Growers 4-7 0 50 100 150 200 Average cost in dollars per acre SOURCE: Washington State University Figure 3 Costs of secondary pest control in pears Cost to control secondary pests ($ / acre) Additional costs of secondary pest control associated with the use of pesticides with high risk to natural enemies in pear orchards without mating disruption. 300 250 Pheromones 200 150 100 50 0 50 100 150 200 250 300 Cost of high-risk pesticides used ($ / acre) SOURCE: Washington State University 24 For pears produced in Hood River, Oregon, we analyzed pesticide use information from nine growers over the three years, 2008 to 2010. Five of these growers used pheromones for codling moth control while four did not. The average pest control cost in Oregon pears was $650, plus or minus $20 per acre, or $365 per acre more than in Washington apples. Growers using pheromones had slightly higher costs per acre ($666) than growers not using pheromones ($631). On average, growers using mating disruption spent $26 more on scale, and $6 more on leafroller control, but $59 per acre less on pear psylla and mites. However, for growers not using pheromones, every $1 spent on a high-risk pesticide cost an extra $0.47 to control secondary pests (Figure 3). This suggests there is value to be captured in pear IPM programs through the conservation of natural enemies. April 1, 2013 GOOD FRUIT GROWER 350 While there was some benefit in terms of pear psylla control of using pheromones for codling moth control, this tactic did not result in a cost saving for control of secondary pests that completely offset the cost of the pheromone. However, similar to what was observed in apple, some pear growers that used mating disruption also continued to apply insecticides for codling moth that are of moderate to high risk to natural enemies. Despite the disruptive impacts of some of these sprays, growers using pheromones typically applied one less spray for pear psylla during the summer, indicating that natural enemies were likely contributing to pear psylla management. There is evidence that this is happening in other pear orchards in Hood River, where growers who switched to use of pheromones are reporting fewer problems with pear psylla. The role of natural enemies in these orchards needs further documentation, but if biological control is contributing to pear psylla control, then this could open up a new era in pear pest management. The cost of pest management is not the only important factor in establishing the value of biological control. If natural enemies can reduce pesticide use, then other aspects such as restricted entry intervals, preharvest intervals, and maximum residue limits may be less of a concern. In our apple examples, the three growers with programs that conserved natural enemies also applied the last insecticide of the season well before harvest. Those pest control programs that showed disruption of secondary pests tended to apply the last insecticide in late July or early August, on average about 60 days later than programs that conserved natural enemies. The economic analyses of apple and pear pest management costs presented here illustrate several benefits for integrating biological control into orchard pest management programs. Apples have a long and successful history with integrated mite control that has resulted in huge economic savings. In contrast, for pear, implementing stable pest management programs that integrate biological control continues to be more challenging. ��� This is the fifth article in an eight-part series highlighting results of a five-year Specialty Crop Research Initiative project to enhance biological control of orchard pests. The project involves researchers from Washington State University, Oregon State University, University of California Berkeley, and the U.S. Department of Agriculture in Yakima, Washington. www.goodfruit.com