Spider mites, especially the European red mite (ERM), can greatly reduce grape yields. In many cases predator mites can keep spider mites under control.
It was thought that the predator mite Typhlodromus pyri did not occur on Long Island, New York, so it was introduced into vineyards there in 1996. The mites rapidly established, successfully overwintered, and were able to suppress ERM populations. A year later, when plots were sampled in 1997, there were no ERM in any of the samples from the release plots, while ERM popluations were as high as 50/leaf in one non-release plot.
T. pyri populations declined or remained the same from July to September in the release plots, suggesting pesticides used on the grape plants had an adverse effect on the predator mites.
Some T. pyri were found in non-release plots. Because this mite has a very low dispersal tendancy, it was unlikely that they moved from release plots. More likely T. pyri was already present on Long Island, but in very low numbers.
Releases of T. pyri in other areas where this predator mite is not common have the potential to substantially improve biological control of ERM and other spider mites on grapes.
New York State Integrated Pest Management Program Annual Report, 1998
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