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Ask Ruth: Organic Horticultural Oil for Fruit Trees

August 27, 2012

Dear Ruth,

I missed the first spraying (dormant oil) for my fruit trees. When should I spray them and what do I use? Do I trust any spray labeled “organic”?  I have dwarf apple, peach, pear, plum, and nectarine trees and I live in Pitt County in Eastern NC. Thanks in advance for any advice on this matter.

~Gayle Morgan, Pitt County 

Dear Gayle,

Talking about fruit trees is like opening a can of worms – it is a huge and complicated subject. Generally fruit trees are considered a higher maintenance adventure than other gardening endeavors, but the rewards are oh-so-sweet. Each fruit has its own special needs, and organic approaches to orcharding evolve every year.

Horticultural oils are used to smother insects and their eggs and to suppress overwintering diseases. Opinions vary about exactly when to spray dormant oil, and suggestions ranged from midwinter to late winter/early spring before the buds have begun to swell. Other recommendations were much more specific such as: when green tip is ¼ to ½ inch long (the buds are open at the tip and green is beginning to show).

In the mountains of North Carolina this usually occurs in February/March and probably earlier in Pitt County, NC. Lighter- weight horticultural oils (like all-seasons oil) may be sprayed anytime of year, using caution since sometimes the oil will damage plant leaves.

For horticultural oil to be effective, the oil must contact and coat the pest; complete coverage of the tree is very important, including the crevices/cracks in the tree’s bark and buds. Scale, mites, pear psylia, and aphids are some of the insects targeted by horticultural oil.

Oils should not be sprayed on plants when freezing weather is expected. Refrain from spraying during windy weather since much of your spray will be blown off course by the wind and will not end up on the tree. Likewise avoid rainy weather. If you spray just before a heavy rain, you will have to re-spray following the rain.

The spray you use should be mixed fresh each time you spray, so mix up only the amount you will use right then. Agitate the oil in your sprayer frequently so that it remains in suspension. You want a very fine mist of oil, not blobs. You will need one to two gallons of spray per 8-10’ tree when you are spraying dormant trees. If your trees are super-small, you could get by with a hand-held plant mister (your hand will cramp up pretty quickly if you have very much to spray). A two gallon pump sprayer works well in most garden situations. Be sure not to overfill past the fill line on the tank – or the gasket may blow.

I personally love using a backpack sprayer (3-, 4-, or 5-gallon), but they are a bit costly with about a $100 price tag. Having a sprayer with a wand is extremely useful for reaching into all the nooks and crannies and under leaves.

In lieu of dormant oil, organic orchardist Michael Phillips mixes up a concoction of diluted 100% neem oil with a tad of soap emulsifier, liquid fish, effective microbes, blackstrap molasses, and liquid kelp. On a warmish day, he thoroughly coats the tree and sprays the soil area in the tree’s dripline too.

Here is a list of a few OMRI Approved Oils. (Some may state restrictions for Certified Organic growers):

  • Monterey Horticultural Oil (previously called SAF-T-SIDE):  80% mineral oil (92% unsulfonated residue of mineral oil) for control of fungal diseases, insects and mites. For year round usage-dormant and growing season. Use on most crops, including fruit and nut trees, vegetables, berries, ornamentals, grasses. Controls powdery mildew, mites, scale, botrytis, leafminers and more.
  • Golden Pest Spray Oil – OMRI: 93% soybean oil.  For Fruits, nuts, evergreens and woody shrubs. Controls mites, sooty mold, scale, whitefly, and mealybug.
  • Bayer Advanced Natria™ Multi-Insect Control Concentrate – OMRI: 96% Canola Oil
  • Concentrate Worry Free® Brand Vegol™ Year-Round Pesticidal – Oil – OMRI: 96% Canola Oil. For dormant and growing season use to control all stages of insects and eggs for roses, flowers, fruits, vegetables, houseplants, and trees.
  • Ahimsa Organics Neem Oil *- OMRI: 100% Neem Oil. Note: This is pure, unformulated oil and is not registered for use as an insecticide, fungicide or for any specific herbal use. Use as an insecticide would need to be cleared with your certifier.
  • Organic JMS Stylet Oil – OMRI: 97.1% paraffinic oil (superior grade white mineral oil). Used to control fungal diseases, insects and mites.

Note: ALWAYS check any product you intend to spray for suitability to your objective (does it target the pest you want to target?). Also check for safety precautions, mixing precautions, and general precautions – and follow the safety measures indicated on the product. Pesticide rules and organic rules change over time. Determine the current status of a product prior to use. Certified growers can check with their certifying agency.

Useful Links/Sources:

Local Apples: Photo by Ruth Gonzalez

Other considerations for orchard health:

  • Because of their smaller stature, dwarf (8-10 ft.) and semi-dwarf (12-15 ft.) fruit trees are easier to spray, prune, and harvest.
  • Choose your location carefully – most fruit trees require full sun for good fruit production. Plant fruit trees halfway down the slope where they will enjoy good air drainage. Don’t plant at the bottom of a slope, or in frost pockets, where frost is liable to collect. In mountain locations where spring weather is sporadic, a northeast-facing slope makes an ideal orchard site – because northeast slopes stay cool longer in the spring and therefore the risk of frost damage is reduced.
  • Prepare your planting hole well. Dig a generous wide hole, and plant your tree no deeper than it was in the pot. Backfill the hole with 50% native soil mixed with 50% compost. Soft rock phosphate, greensand, kelp and/or azomite can be added to the backfill as well.
  • Water your fruit tree religiously for the whole first year and (after the first year) during dry periods. Water deeply to the bottom of the rootball. Most trees enjoy moist well-drained soil.
  • Plant disease-resistant cultivars. Plant fire-blight resistant apples and pears.
  • Check your pH. Ideal pH for many fruit trees is 6.5. Soil that is too acidic contributes to fire blight susceptibility.
  • Don’t over-fertilize. Too much nitrogen produces succulent growth that is more susceptible to insects and diseases – such as fire blight.
  • Employ good sanitation throughout the year. Pick up and dispose of fallen fruit. Rake up fallen and diseased leaves. Destroy diseased fruit, diseased branches, and diseased leaves (do NOT compost).
  • Prune fruit trees regularly to maintain good air movement, and fruit access to sunlight.
  • When fruit trees are in bloom, don’t spray insecticides since pollinators (such as honeybees) could be killed by the insecticide. I think it is always safer to spray oils very early or late in the day, so that the risk – of bee traffic and plant injury from sunburn – is minimized.

Gayle, not all organic products will be labeled OMRI, and restrictions apply to some OMRI-labeled products, but seeing OMRI on the label does help you quickly discern whether the product is considered organic. There is also an EPA label with three little leaves that reads “For Organic Gardening”. Click here for more information on the EPA label. Some companies, such as Seven Springs, label various products as NOP (National Organic Program) compliant.

Look for organic products in your local garden center/agricultural supply. If you cannot find the product locally, try Seven Springs Farm, Johnny’s Selected Seed, Peaceful Valley Farm Supply, or Harmony Farm Supply.

Best wishes,
Ruth

PS: Put the 2013 Annual OGS Spring Conference (March 9 & 10) on your calendar – this is our 20th year and cause for celebration!

Gardeners: Got a question for Ruth? Email it to us at enews@organicgrowersschool.org.
Ruth Gonzalez is a former market farmer, gardener, local food advocate, and founder of the Tailgate Market Fan Club where she blogs at tailgatemarketfanclub.wordpress.com. In her job at Reems Creek Nursery, Ruth offers advice on all sorts of gardening questions, and benefits daily from the wisdom of local gardeners.

Ask Ruth © 2012 Ruth Gonzalez & Organic Growers School

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2 Comments leave one →
  1. Pat Momich permalink
    August 31, 2012 1:04 am

    Ruth, Is there a reason you omitted 5th Season in Asheville as a good source for organic products? -Pat

    • September 3, 2012 4:23 am

      Hi Pat,

      No, I simply said ” Look for organic products in your local garden center/ agricultural supply” with the idea of encouraging local purchases without having to individually name every single local garden center and agricultural supply (since there are quit a few). Fifth Season is a good source for organic products. Reems Creek Nursery also sells organic products, and I am sure all of our local independent garden centers carry a variety of organic products. The beauty of supporting a local independently-owned store – besides keeping your money circulating within your own community – is that the staff at these stores can be very knowledgeable about local gardening issues and a great source of information.

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