Agriculture Reference
In-Depth Information
approach to pears, based on recent research that had been done on
codling moth life stage models and plant pathogen predictive models.
Aphids, scales, psylla, and mites join codling moth to attack pears. After
DDT was banned, the standard pest-management regime was a toxic
jumble of fourteen different organochlorine, organophosphate, and car-
bamate pesticides that wreaked havoc on natural enemies. Davis set out
to rationalize this. He developed a codling moth control strategy using
azinphosmethyl in low dosages timed precisely to be on the tree when the
larvae hatched and migrated to fruit. He drew on earlier research that
demonstrated codling moth could be controlled with half the label rate
that would allow the survival of natural enemies for other pests. For
Davis's plan to work, growers were going to need to know a lot more
about the status of pests in their orchards, e.g., when they were biologi-
cally vulnerable to pesticides. The first step was to help “field men”
understand how to use monitoring traps to understand the development
of the codling moth.
Davis was able to use some of his USDA funding to hire pest-control
experts and train them with his method, working with George Post and
Pat Weddle, among others. Weddle was finishing his graduate work in
entomology, and began working with Doug Hemly's father, who had
himself collaborated with Cooperative Extension researchers for many
years. Davis structured the program so that growers would be reim-
bursed for the expense of employing pest monitoring experts: 75 percent
the first year, 50 percent the second year, and 25 percent the third year,
inculcating them with the value of monitoring and scientific entomolog-
ical knowledge. This program was so successful that it played a role in
the creation of the PCA licensing system. As this project was drawing to
a close, Davis codified this knowledge into the first crop-specific IPM
manual in California.
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The codling moth is a major pest of apples, pears, and walnuts, so
its food and sex practices have received an extraordinary amount of sci-
entific attention. During the 1980s, scientists researched the precise
chemistry of the sex pheromone and the behavioral response of males.
Once evening temperatures reach 62ºF in the spring, females release a
pheromone plume that can be detected up to one-fourth of a mile. The
males zigzag the boundary of the plume until they are within a few
millimeters and make visual contact with the female, when they initiate
