Use of Horticultural Oils for Mite Management in Fruit Orchards

Use of Horticultural Oils for Mite Management in Fruit Orchards

Summary

Three horticultural oils–Stylet oil, Damoil, and Mite E-oil–and two methods of application (complete sprays vs. alternate row middle applications) were evaluated under commercial fruit orchard conditions. In two orchards, multiple applications of Stylet oil were compared with the grower’s standard mite management program, while in the third orchard various horticultural oils were evaluaated to compare their mite control efficacy. Under high mite pressure the horticultural oil treatments applied as complete sprays were effective in controlling mite populations. Applications of oils as alternate row middle sprays with reduced volume of water did not provide adequate mite control. No negative effects (phytotoxicity) on fruit finish were observed in orchards treated with summer oils.

Objectives/Performance Targets

1) Field documentation of the effectiveness of various summer horticultural mineral oils for mite control on various fruit crops and at the same time test for phytotoxicity effects;

2) As a result of field demonstrations and publication of educational materials, at least 50 growers will incorporate summer oils as part of their mite control strategy.

Accomplishments/Milestones

1. Three cooperating growers were identified and an experiment was located in each of their commercial orchards.

2. Season-long mite and mite predator data from each orchard were collected.

3. The oil programs provided comparable seasonal mite control in contrast to conventional acaricides, and no adverse oil effect on fruit or foliage was observed.

4. Approximately 400 fruit growers learned about this project during educational meetings.

5. Participating growers are willing to continue the program during next season, and additional growers are interested in participation in the program.

Impacts and Contributions/Outcomes

During the 2002 season, the efficacy of three horticultural oils was tested in commercial fruit orchards. In Grower A orchard, the standard mite program included two alternate row middle applications of clofentezine at pink and petal fall followed by a complete application of pyridaben in late June. The oil block received five complete applications of Stylet oil. The early season oil applications suppressed the mite population until the beginning of July when the number of mites increased to more than seven per leaf. The “emergency” oil application on July 10 lowered the number of mites to two motile forms per leaf during the July 15 evaluation. The mite population in the oil-treated block remained at a low level for the rest of the season. In the standard block the pyridaben application lowered the mite population immediately after the treatment.

In late July, mites recovered again, reaching more than four mites per leaf during the July 25 evaluation. Although the predatory mites were present in both programs, a higher predatory mite population (per leaf) was observed in the oil treated block. It appears that in both programs the abundance of predatory mites contributed to successful control of late season mite populations.

In Grower B and Grower C orchards, the mite populations on ‘Golden delicious’ trees in both programs were at very low levels during the entire season. On ‘Yorking’ trees, three oil applications applied in late May and June suppressed the mite population to less than two mites per leaf throughout the season. Mite populations in blocks with standard management programs were at higher levels. The comparison of various horticultural oils documented similar mite control efficacies. Horticultural oils applied as alternate row middle sprays did not provide sufficient mite control.

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