Use of Horticultural Oils for Mite Management in Fruit Orchards

Use of Horticultural Oils for Mite Management in Fruit Orchards

Summary

Three highly refined horticultural summer oils: JMS Stylet oil (JMS Flower Farms, Inc.) Mite E-oil (Helena Chemical Company) and BioCover LS (UAP Platte Chemical Company) and two methods of application (complete sprays vs. alternate row middle applications) were evaluated for European red mite control in four commercial apple orchards . In two orchards multiple applications of Stylet oil were compared with the grower’s standard mite management program while in the remaining two orchards the horticultural oils were evaluated side-by-side to compare their efficacy for mite control. Under high mite pressure the JMS Stylet oil treatment applied as complete sprays with full volume of water (100-150 gal/acre) was very effective and provided excellent mite control. During later part of the season high numbers of predatory mites: Amblyseius fallacis and Zetzelia mali were also observed on treated trees. Applications of horticultural oils performed as alternate row middle sprays with reduced volume of water did not provide adequate mite control. After significant mite’ build–up despite oil applications during the early part of the season, an increase in water volume and oil concentration did not reduce the mite population to below the threshold level. The late season increase in the number of mites per leaf resulted in visible bronzing of leaves. Standard acaricide applications were necessary to avert the possible crop loss. No negative effects (phytotoxicity) on fruit finish were observed in orchards treated with summer oils.

Objectives/Performance Targets

Project 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

Milestones accomplished during the 2003 season:
1. Four 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, no adverse oil effect on fruit or foliage was observed.
4. Approximately 350 fruit growers learned about this project during educational meetings.
5. Participating growers, despite the termination of the research program are interested in continuation of the program in the future. Adjustments will be made in the oil usage for mite control program to incorporate the 2003 and 2002 findings.
6.The results of the experiment were presented to interested fruit growers and representatives of ag chemical industry. Contacts were established to incorporate more diffrent kinds of horticultural oils into regular mite and insect control. Newly developed horticultural oils will be tested during next season.

Impacts and Contributions/Outcomes

Outcomes: During the 2003 the experimental plots were located in four commercial apple orchards located in Franklin and Adams County, PA. Only orchards with historically high, established European red mite population were designated for the use during the study. The single Franklin County orchard had been using summer oils for mite control during last few years, while the Adams County sites did not use summer oils for mite control in the past. Despite the history of mite problems in the past, during the 2003 season the phytophagous mite populations in two orchards located in Adams County did not develop above the threshold levels either in oil treated or standard treated blocks. Although the mite counts were performed during the entire season, the findings from these two orchards where oil treatments were applied as the alternate row middle applications are not being discussed in this report.

In the Franklin County orchard blocks with “Stayman” and “Red Delicious” trees were used for the observation; in the oil block the complete applications of JMS Stylet oil were done four times during the season. The standard block received a complete application of abamectin and oil at petal fall and two alternate row middle applications of bifenazate late in the summer. The Adams County orchard consisted of two varieties “Golden Delicious“ and “Yorking”. The orchard was divided into four 5 acre blocks and each part was treated with different summer oil: JMS Stylet oil, BioCover oil and Mite-E-Oil. Standard block did not receive oil treatment during the season but received a complete application of clofentezine at the petal fall. The assortment of pesticides for the evaluated blocks was based on the individual compound toxicity toward the mite predators and compounds with the lowest activity against mite predators were selected for insect and disease control. Starting after the bloom, in each evaluated block the mite and mites’ predator data was collected throughout the entire growing season.

In the Franklin County orchard treated with oil, the early season oil applications suppressed mite population until late July when the number of mites on “Red delicious” and “Stayman” trees increased to about 6 mites per leaf. The “emergency” oil application on July 29 lowered the number of mites to less than 2 motile forms per leaf for the remaining of the season. During late July and August significant built-up of phytoseid and stigmaeid mite predators was observed in oil treated blocks reaching up to one predatory mite per leaf. The standard blocks required an application of the bifenazate to lower the phytophagous mite population. Although the predatory mites were present also in standard program, a higher predatory mite population (per leaf) was observed in the oil treated block. It appears that the abundance of predatory mites was essential to successful mite control on oil treated trees.

The Adams County orchard was used for side-by-side comparison of various summer oil treatments applied through the season. The JMS Stylet Oil, BioCover Oil and Mite E-Oil applications using 1 percent solution were made on 13 May (at 100 gal/acre), 16 June (100 gal/acre), 7 July (150 gal/acre) and 18 July (200 gal/acre). In July, despite very intensive oil programs the phytophagous mites reached more than 20 mites per leaf and standard acaricides (pyridaben and clofentezine) were necessary to lower the number of mites. Despite observed increase in the number of mite predators in oil treated blocks, the beneficial mites were not able to suppress these high numbers of mites.

Collaborators: