Use of Horticultural Oils for Mite Management in Fruit Orchards

Final Report for LNE02-159

Project Type: Research and Education
Funds awarded in 2002: $39,281.00
Projected End Date: 12/31/2004
Matching Non-Federal Funds: $15,419.00
Region: Northeast
State: Pennsylvania
Project Leader:
Dr. Greg Krawczyk
PSU, Department of Entomology, FREC
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Project Information


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 Pennsylvania commercial apple orchards during a two year period. In some orchards multiple applications of Stylet oil were compared with the grower’s standard mite management program while in other 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 parts of the season high numbers of predatory mites, Amblyseius fallacis and Zetzelia mali, were 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 ARM 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.

Performance Target:

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 fruit and foliage phytotoxicity effects;

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


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  • Larry A. Hull


Materials and methods:

The experimental blocks were located in commercial apple orchards 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 prior to the project, while the Adams County sites did not use summer oils for mite control in the past.

During the 2002 season, the early season application of dormant oil was applied in early April in each orchard. Blocks used for the oil experiment on Grower A farm consisted of one apple cultivar ‘Red delicious’ (15+ year old). On Grower B farm, a 10 acres orchard with ‘Yorking’ and ‘Golden delicious’ was divided into two similar blocks and the oil program was applied in one block. The experiment at Grower C site involved 4 separate apple bocks (? five acres each) with three of the blocks being treated with different horticultural oils and the fourth block being used as a control. Each block had two apple varieties ‘Yorking’ and ‘Golden delicious.’ During the summer oil applications Grower A, B and C used Stylet oil (JMS Flower Farms, Vero Beach, FL) while Grower C also used Damoil (Drexel Chemical Co., Memphis, TN) and Mite-E-Oil (Helena Chemical Co., Memphis TN).

Due to various past experiences with the mite pressure in orchards, the horticultural oil programs were different at each site. While the dormant oil application was applied in each orchard as a standard, the later in-season applications varied among orchards. In the Grower A orchard, the JMS Stylet oil was applied on 11 and 29 May, 10 and 20 June, and 10 July. The Standard block received an application of clofentezine on 11 May and an application of pyridaben on 20 June. In the Grower B standard program no conventional acaricides were applied the entire season while the JMS Stylet oil block had applications of the oil on 30 May, 13 and 27 June. In Grower C orchards all 4 treatments received an application of clofentezine on 6 May and then the oil program blocks received various oil treatments on 3, 13 and 18 June. No conventional acaricides were needed in the standard block during the season. All oil applications by Growers A and B were done as complete sprays using 100 gallon of water per acre (? 934 l/ha), except for the Grower A 10 July application when 200 gal of water was used per acre. Grower C applied tested oils as alternate row middle applications using 50 gallons of water per acre. At each farm, blocks used for oil efficacy evaluations were treated with the same insecticide and fungicide programs as the standard blocks.

Mite and mite predator densities were evaluated on a weekly basis and compared to mite populations in blocks with standard program. During each observation leaves for counts were collected from eight trees scattered throughout each block. At least 25 leaves per tree (200 leaves per block) were evaluated using a leaf brush machine for the presence of phytophagous mites, predatory mites (Amblyseius fallacis and Zetzellia mali) and mite eggs. Each variety was also visually evaluated and rated during the harvest for phytotoxicity of oils on fruit and foliage.

Research results and discussion:

1. 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 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. Growers participating in the program, despite the termination of the research remain highly interested in the continuation of the oil program in the future.

5. Based on information received from oils distributors, it is estimated that majority of PA fruit growers used summer oils during the 2004 season either as a stand alone mite treatment or as a part of other pesticide/acaricide treatments. The horticultural summer oils become accepted as a standard pest control procedure (i.e., no phytoxoxicity concern).

6. The results of this project were presented to the international audience at the 6th International Conference on Integrated Fruit Production in Baselga di Pine, Italy (September 26-30, 2004)) and during the 2004 NE SARE Conference “Setting the Table: Tools and Techniques for the Sustainable Food System” in Burlington, VT (October 19-21, 2004).

Participation Summary


Educational approach:

In addition to multiple presentations of the results to Pennsylvania fruit growers during winter IPM meetings (10-14 meetings with the audience of 20 to 150 growers) and seasonal twilight pest updates (8-10 meetings each season) conducted by the Author the results of this project were presented to the international audience at the 6th International Conference on Integrated Fruit Production in Baselga di Pine, Italy (September 26-30, 2004) and during the 2004 NE SARE Conference “Setting the Table: Tools and Techniques for the Sustainable Food System” in Burlington, VT (October 19-21, 2004). The results of the program are also being submitted for publication in IOBC/WPRS Bulletin.

No milestones

Additional Project Outcomes

Project outcomes:

Impacts of Results/Outcomes

During the 2002 season in Grower A orchard, the early season oil applications suppressed mite populations until the beginning of July, when the number of mites increased to more than 7 mites per leaf. The “emergency” oil application on July 10 lowered the number of mites to 2 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 4 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 the abundance of predatory mites contributed to successful control of phytophagous mites late in the season.

In Grower B and Grower C orchards in Adams County, 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 2 mites per leaf throughout the season. Mite populations in blocks with standard management programs were at higher levels. Horticultural oils applied as alternate row middle sprays did not provide sufficient mite control.

During the 2003 season 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 control of other pests and diseases in rach evaluated orchard was based on the individual compound selectivity 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.

Similarly, during the 2002 season, in the Franklin County orchard treated with JMS Stylet 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 reduce 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.

Despite the history of mite problems in the past, during the 2003 seasons 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.

Farmer Adoption

Grower Adoption Survey

To evaluate the impact of the project, two grower surveys were conducted during the winter of 2001/2002 (before the beginning of the project) and during winter of 2004/2005. The questions included in the survey were developed to better understand the actual positioning of oil treatments in standard pest control procedures conducted in fruit orchards. During the first surveys106 growers from 7 different fruit growing regions were asked question about patterns of horticultural oil usage during a) dormant applications; b) summer applications; c) as treatment to control mites; d) as addition to enhance other compounds; and e) if growers intend to use horticultural oils as a mite control tool during the incoming season. During the second survey, a group of 145 growers from five different fruit growing regions was asked the same set of questions. The second survey was conducted after the project was over and results were shared with the stakeholders during extension IPM meetings.

During both surveys close to 90 percent of responders declared that they use oils during dormant period (89% during 2002 and 97 % during 2005 surveys). The Damoil and Superior Dormant Spray Oil (from UAP –Loveland Industries) were the preferred choices during both years for dormant application. A significant increase in summer oil usage was reported during the 2005 survey (41% vs 50 %) with the majority of the growers using the summer horticultural oils either as a separate treatment to control mites or as an addition to enhance other compounds activity. While asked about their plans to use the summer horticultural oils for mite control during incoming summer, during the 2005 survey 32 percent of the growers declared the intend to use oils for this purpose. During the 2002 season, before the initiation of the project, only 17 % of the growers declared to use the summer oils for mite control during the incoming summer season. The preferred summer oils include SunSpray UltraFine Oil (Sonoco), JMS Stylet Oil and Bio-Cover Oil (UAP-Loveland product, Inc).

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.