Good Fruit Grower

April 1

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Enhanced Biocontrol Figure 1 Apple pest control costs Average pest control costs of Washington apple growers using programs that conserve natural enemies (growers 1-3) compared to those whose programs included pesticides with high risk to natural enemies (growers 4-7). Over the last four decades, integrated mite control has saved Pacific Northwest apple growers millions of dollars each year. by Karina Gallardo and Jay Brunner, Washington State University; Steve Castagnoli and Peter Shearer, Oregon State University T he value of biological control in Washington State orchard systems has been well documented in apple, but its value has been harder to demonstrate in pear. In apple, there are several examples of how natural enemies have successfully controlled pests, even in an environment where pesticides were used to control other pests, like codling moth and leafrollers. Washington State University entomologist Dr. Stan Hoyt developed integrated mite control in the late 1960s (see ���How integrated mite control works���). Over the last four decades, integrated mite control has saved Washington fruit growers millions of dollars each year because they did not have to use specific miticides to control spider mites. National surveys of pesticide use in apples show that, over the last 20 years, an average of 24 percent of the Washington acres were treated annually with miticides. By comparison, 76 percent of Michigan and 70 percent of New York apple acres, on average, were treated annually with miticides. Washington apple growers have also benefited from biological control of the western tentiform leafminer and the white apple leafhopper. These natural enemies are somewhat unique because they have developed a tolerance to certain organophosphate insecticides. Apple and pear orchards have changed as regulatory actions have phased out or restricted the use of many organophosphate insecticides. Alternative insecticides have taken their place, and we are only just beginning to understand their impact on natural enemies. Our project looked at the impact of several organophosphate-alternative insecticides plus some fungicides on eight natural enemies. Results showed that the reduced-risk attributes of these organophosphate alternatives apply to humans but not necessarily to natural enemies. Integrating biological control has been more challenging in pears. Average pest control cost per acre Calculating the value of biological control Growers 1-3 Growers 4-7 500 400 300 200 100 0 Year 1 Year 2 Year 3 SOURCE: Washington State University To better understand the economic value of biological control in apple and pear orchards, we analyzed pest control records from several growers over three years. We calculated both the cost of each pesticide and the application cost. We identified the target(s) for each pesticide and rated its risk (low, medium, or high) to natural enemies. By taking this approach, we could measure the disruptive effect on natural enemies of different pest control programs by the need to apply controls for secondary pests (aphids and spider mites in apple, and spider mites and summer pear psylla in pear). Apples For apples in Washington, we analyzed pesticide use information from seven growers over three years, 2007 to 2009. The average cost of insect and mite pest control over all years was $286, plus or minus $39 per acre, with an average of nine pesticides being applied. We examined the relationship between the use of pesticides with high risk to natural enemies and pesticides used to control secondary pests. We found that for every $1 spent on a high-risk pesticide, it cost an extra $0.52 to control secondary pests. Three of the seven growers (growers 1-3) had transitioned away from organophosphate insecticides and had a stable integrated pest management program relying on pheromones and low-risk organophosphate alternatives. Their average pest control program cost over three years was $166 per acre, with little change over time (Figure 1). These growers had an average cost of $5 per acre for secondary pest control and used no high-risk pesticides in years two and three (Figure 2). The average pest control program cost for the other four growers, growers 4-7, was $377 per acre, but their costs increased over three years (Figure 1). These growers had an average cost of $113 per acre for high-risk pesticides and HOW integrated mite control works 22 April 1, 2013 GOOD FRUIT GROWER The alternative food source allows predatory mites to survive during periods of low pest-mite densities. The same principles of integrated control were implemented in other apple growing regions throughout the United States and Canada, but never with quite the same degree of success as the arid growing regions. The comparatively low incidence of disease problems, and hence lower fungicide use, greatly helped implementation of integrated control in the West. Apple maggot and plum curculio were not present, and the overall pest complex required a less intense spray program. In addition, the western predatory mite is a one of the more efficient mite predators, and is well adapted to dry conditions. Other phytoseiids do not have the same high reproductive rate; and other predators, such as the Stethorus beetles, are usually not attracted to mite populations until after high populations have already developed. ���E. W. Beers, WSU photo courtesy of elizabeth beers, wsu B y the late 1950s, mite outbreaks had reached a crisis stage in Washington���s apple orchards. New miticides were introduced regularly, but mites (the most important of which at that time was McDaniel mite) became resistant, sometimes within a few years. Despite four to six miticide applications, damage still occurred. Dr. Stan Hoyt, entomologist with Washington State University in Wenatchee, began working on this problem, and discovered that the western predatory mite, Typhlodromus occidentalis (also known as Galendromus occidentalis), could effectively control spider mites under certain conditions. The most important aspect was to minimize the use of pesticides toxic to the predator. These included high doses of organophosphates, such as azinphos-methyl (low doses were selective because the predator had become resistant); carbamates such as carbaryl; sulfur fungicides (especially after bloom), and nonselective miticides. The second key was minimizing the use of pesticides toxic to the alternate prey, apple rust mite, which included many of the same chemicals (nonselective miticides, sulfur fungicides, carbaryl, and endosulfan). One of the keys to integrated mite control was that the western predatory mite Typhlodromus occidentalis could effectively control spider mites under certain conditions. In the picture, a ���typh��� attacks the larger European red mite.

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