Mite Counting and Pyramite Trial

Project Title

On Farm Research Evaluation of Pyramite (pyridaben) for Spider Mite Control on Apples.

Start Date and Duration

July thru September, 1997

Investigator/ Collaborators

WSU Nooksack Watershed IPM Project with grower collaborator:

John and Dorie Belisle

Funded by Environmental Protection Agency, Clean Water Act, Section 319 Grant; administered by Washington State Department of Ecology.

Project Description/How was it done?

This project developed from a workshop held on the Belisle property in mid-July. This workshop focused on scouting techniques and desision making for major insect and mite pests in apples in Whatcom County. Growers participated in collecting leaf samples from the orchard, brushing them with a mite brushing machine, and mite identification and counting under a microscope. This initial count done on the farm indicated a building population of twospotted spider mites (TSSM) and eggs and the abscence of predator mites, which is common in young orchards. With continued grower involvement in sample collection and labwork, five more samples were collected on a weekly basis through early September. This allowed a grower to become more familiar with this mite counting procedure with technical assistance from the Nooksack IPM Project manager and to eventually evaluate the field efficacy of Pyramite, a recently registered miticide in apples. Pyramite was applied on 8/22 (3.3 oz. product /100gal water/acre) to control a population of TSSM which had reached 102 mites/leaf and 143 eggs/leaf. At the time of this application, the population exceeded recommended treatment thresholds which are approximately 25-30 mites/leaf.

Results

The attached data sheet shows spider mite and predator mite densities at each sampling date from the most heavily infested portion of the orchard. Due to the widespread distribution of TSSM in this orchard, the entire orchard was treated, leaving no untreated control are for comparison. Pyramite reduced TSSM mobile stages by 70% within 10 days of application and by 90% three weeks after spray. TSSM egg counts declined by 23% within 10 days, and 95% three weeks after the spray. This material has activity agains recently hatched immature stages of spider mites. It acts by blocking cellular respiration, which causes spider mites to lose coordination and eventually collapse. Mites do not reach maturity and therefore, there is no replacement of eggs which declined significantly but over a longer period. The western predator mite, Typhlodromus occidentalis, was increasing in density prior to the spray but this response was too late for effective spider mite control. Pyramite did not appear to have a significant detrimental impact on predator mite populations. Sub-economic rust mite populations (160/leaf) dropped to 10/leaf within 10 days of the Pyramite application.

The grower gained an appreciation for the detailed nature of the mite counting procedure and with minimal additional training would be capable of performing these tasks quite accurately. As with many activitied, increased accuracy in mite counting and identification comes with experience.

Any problems or limitations?

No

What did we learn?

Certain, initiated growers are interested in laboratory mite counting, and with minimal additional training and experience, they could provide such a service to others.

Pyramite controls TSSM and rust mites with no observed impact upon T. occidentalis, a common predator mite in apples.

Where do we go from here?

Investigate opportunities to support growers who are interested in continuing to use this tool for mite management, and as a tool to evaluate the impacts of pesticide sprays to the orchard pest and predator mite complex.

Belisle mid block

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