Use of dormant oil on fruit trees

kudzu9(Zone 8a - PNW)March 5, 2008

I have about a dozen fruit trees and two of them had problems last year that are treatable with dormant oil. I sprayed once about 2 weeks ago, and now the trees are starting to bud. I'd like to do a follow-up spraying. I have heard two things about dormant oil: 1) you can spray any time, and 2) you shouldn't spray when they are budding. Anyone care to comment on which is correct?

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Dormant oil is not a toxic substance, and works by cutting off the oxygen to overwintering eggs of insects and, to a certain extent, fungal organisms that require oxygen to survive. It is quite effective against things like scale insects and aphids, but much less so against fungal problems like apple scab, peach leaf curl, or bacterial diseases.

What are the particular problems you are trying to treat with dormant oil?

When applying oil, you might first consider the strength of the mix, as well as the type of oil you are using. When spraying fully dormant trees, I use a strong mix of up to 5 ounces of paraffin-based oil per gallon. Lately, I have been using standard Bonide spray oil. Yes, you can spray with oil "any time", but after trees are leafed out you would want to use a lighter, summer weight oil such as Sunspray, and mix at a much lower rate -- say one ounce per gallon or less. Otherwise, spray oils can be phytotoxic and will burn the leaves.

Generally, dormant oil sprays are most effective when the trees are ready to bud out, and the insect organisms are also waking up. I would have no reservations at spraying trees that are beginning to show bud color, but would probably reduce the mixing rate to 3 ounces per gallon or less when using a standard, paraffin-based oil.

If you can find a weather window of at least 2-3 days with no rainfall, oil sprays will be more effective. Maybe not so easy in your area. Full coverage is also important with oil sprays, so wait for a calm day when you can focus the spray and really see what you are doing. I always mix my oil sprays with copper (Kocide) to deal with fungal as well as insect problems. The two seem to work well together, and I use this mix on both pome and stone fruits.

Don Yellman, Great Falls, VA

    Bookmark   March 5, 2008 at 1:24AM
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rcnaylor(z7 Tex)

I've used it before and had good success, but, wanted to thank Don for a timely reminder of good info.

    Bookmark   March 5, 2008 at 7:54AM
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calistoga_al ca 15 usda 9

Time your spraying for the coolest time of day to lesson the chance of leafburn. Al

    Bookmark   March 5, 2008 at 9:38AM
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bart1(6/7 Northern VA)

Don -
Is the copper that you use liquid or powder? I did some spraying this weekend (dormant oil, lime/sulfur, and copper) and the copper was the only power ingredient and I had some sprayer clogging problems. I've since discovered some liquid copper in one of fruit tree catalogs. Should I switch to that?


    Bookmark   March 6, 2008 at 2:23PM
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Liquid copper products sold in fruit tree catalogs (such as Bonide) normally have a much lower fixed copper equivalent, (which is the only standard I have found to estimate the strength of a copper spray), than the Kocide I use. Liquid formulations are also normally much more expensive per application of equivalent coverage.

Kocide is copper hydroxide, and it gets cheaper when you purchase larger packages. I bought a 20 lb. bag that looks like it will last me about 10 years, if I am still spraying 10 years from now. Kocide dissolves readily, and I have never had any clogging problems, though I do rinse off the wand filter from time to time.

I would not use copper sulfate, which is normally sold in crystal form, and is much more difficult to dissolve. I do not pre-mix the Kocide, but add it directly to the backpack sprayer as I am filling it with the hose.

If you want to use a liquid for the sake of convenience, I am sure thay are effective too if you use enough in your mix, but it will cost you significantly more per application.

Don Yellman, Great Falls, VA

    Bookmark   March 6, 2008 at 4:04PM
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bart1(6/7 Northern VA)

Thanks Don!

Should I plan on doing another spray closer to the budding period?


    Bookmark   March 7, 2008 at 7:14AM
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bart1(6/7 Northern VA)

One more question, Don....

What type/strength of Kocide are you using? I found some Kocide 2000 on line and was wondering if that will do the trick.

Thanks again,

    Bookmark   March 7, 2008 at 8:35AM
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The product I am using is called Kocide DF. There are several formulations of this product, and the differences are not clear to me, but I believe they are similar in most respects that are important to the home orchardist.

I plan to do one last application on the stone fruits just at bud break, then I put away the Kocide for the balance of the season. I have no fungal problems, but have had some bacterial spot on the white peach Sugar Giant. White peaches seem particularly susceptible to bacterial spot, which is apparently in my environment all the time. In past years, I had it even on yellow varieties, but the incidence has been greatly reduced. Bacterial spot ruins peaches.

Don Yellman, Great Falls, VA

    Bookmark   March 7, 2008 at 11:52AM
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The use of some pesticide sprays may not be for everyone, particularly organic farming enthusiasts. But we've got to admit, pestcides work. And they're a lot easier than inspecting every branch of every tree in your orchard. This was what one of our "experts" 1851. It was promoted as an affective way to control "catterpillars." Interesting (or humorous), but today I'd stick with sprays, used appropriately with a good IPM program.

Here is a link that might be useful: The Heirloom Orchardist

    Bookmark   March 8, 2008 at 7:09PM
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kudzu9(Zone 8a - PNW)

Thanks for all the great info, Don, and to the others for their questions and input. I got everything I needed and more!

    Bookmark   March 10, 2008 at 4:10AM
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bart1(6/7 Northern VA)

I did a bit of research on the various types of Kocide (copper) that are out there. This may help some of you in the future.

Kocide 101 - 77% Copper Hydroxide (50% metalic copper equivalent)

Kocide DF - 61.4% Copper Hydroxide (40% metalic copper equivalent)

Kocide 2000 - 53.8% Copper Hydroxide (35% metalic copper equivalent)

Kocide 3000 - 46.1% Copper Hydroxide (30% metalic copper equivalent)

I wasn't able to find a source for Kocide 101 online (which has the highest percent of copper) so I went with the Kocide DF. I could only find it in a 20 pound bag for $125 (!!!), but as Don mentioned above, this should last a very long time.

Hope this is helpful to someone.


    Bookmark   March 15, 2008 at 5:37PM
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Hi, guys! My trees were just planted last year, and i have to admit, i've sprayed nothing on them at all yet. Last year, the only problem i identified was some plump aphids on the cherry trees, and i just sprayed those off with the hose. Since i don't know what issues i may be facing this year, i've opted not to spray. Do you think this was a mistake? Is spraying pretty much inevitable?

    Bookmark   March 15, 2008 at 11:37PM
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calistoga_al ca 15 usda 9

The price of anything containing copper is off the charts. Farmers are having the copper stolen from power poles, my son had a vacant house stripped of the wiring in the walls. We all suffer when the source of anything is limited to a few producers. Al

    Bookmark   March 16, 2008 at 11:03AM
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I am trying to find Kocide 101 for purchase, but would settle for the Kocide DF. Where would I be able to buy it online?

I just had two live oaks sprayed with Kocide 101 and the guy charged me an extra $100 because it was Kocide 101 and not a different, cheaper fungicide. I watched his men do the job. They didn't use much powder at all, and they hooked their tank up to my water hose to fill it up. The bio-pack (root feeding) and fungicide spraying cost me $400. I feel like I got really ripped off and would like to do it myself from now on. I bet I can rent a tank/pressurized sprayer somewhere locally and add my own chemicals for a fraction of what I just paid.

I would appreciate any information you could provide on where to purchase the Kocide. I hate being fleeced by "professionals" who prey upon the uninformed and unmotivated masses.

Thanks a lot!

    Bookmark   July 28, 2008 at 2:16PM
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Scott F Smith(6B/7A MD)

Try Johnnys Seeds. Or type Kocide price into Google and get lots of other options. I think Bart above has the exact wrong idea, copper is not good to overdo since it builds up in the soil over the years and is harmful the earthworms once enough has built up. I use Kocide 3000 because it is formulated to do the best job against diseases with the smallest dose of copper. I use it on fruit trees however and don't know if some other Kocide is better for oaks.


    Bookmark   July 28, 2008 at 11:04PM
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Are there any fruit trees that are intolerant of the copper in these recommended sprays. I just bought a three pound bag of CuPro 2005 containing 53.8% copper hydroxide, but the directions on the packet were exclusively for ornamentals. My yard and orchard is highly varied with apples, pears, peaches, blueberries, pomegranates, persimmons, goji, cherries, mulberries, apricots, paw paws, figs, pecans, heartnuts, lemons, satsumas, and oranges(potted for winter removal). ..Would any of these be harmed by a late dormant spraying of dormant oil and the copper hydroxide mix? ...Could anyone reccomend a good mix rate for the copper? I only have a total of fifty or so trees that are fairly young and plan to hand spray them for now.

I am very sensitive to the comment on copper buildup harming the worm population, and would like to limit copper applications as much as possible. I predominately use organic techniques in my gardens, but early problems with the orchard plantings are forcing me to turn toward spraying my young trees. They all receive generous doses of compost, worm compost, and compost teas in the Spring and Fall.

Thanks for your input,


    Bookmark   August 18, 2008 at 2:56PM
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I have the Wison dormant kit ie. liquid oil spray and lime sulphur. Temp now in 10 celcious. My fruit trees are budding. Should I spray now? Should I wait for last danger of frost?

    Bookmark   March 30, 2011 at 5:01PM
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