Tis the Season for Dormant Fruit Tree Sprays

Spraying gear.

Actually, tis almost past the season, and I sprayed the trees a week and a half ago, but four baby chicks have distracted my attention away from writing about fruit trees. Fruit tree care is one of Kelly’s many areas of expertise (I attempted unsuccessfully to sweet-talk her into writing this post and picked her brain extensively). This was the first year that I donned a surgical mask and my rattiest pair of corduroys and braved the copper and horticultural oil.

There are a number of reasons to spray some fruit trees with copper and oil. While the copper acts as a general fungicide, helping to prevent everything from peach leaf curl, to brown rot, to rust, to fire blight, oil serves as a spreader-sticker that also kills overwintering insects like wooly apple aphids.

Spraying before the trees bloom is important because copper is toxic to bees and other pollinators, and horticultural oil will smother them. For some diseases, however, you will have to spray while the tree is in bloom. Fire blight and brown rot are both examples. In this case, it is best to time your spray to hours of the day when foraging insects are most likely to have returned home.

As someone who had never sprayed anything other than fish emulsion before, I can assure you that I found the prospect somewhat daunting and that I only agreed to it because Kelly was out of town and I was afraid the flowers would open before she returned. As a newly minted “veteran sprayer,” I can say that it wasn’t all that bad, and I’ll even go out on a limb and say that anyone can do it. In that spirit, allow me to explain the process.

Trees to spray

Not every fruit tree should be sprayed with copper and horticultural oil, and trees that may benefit from spraying in one climate, don’t need to be sprayed in others. Persimmons, pomegranates, mulberries, and citrus are examples of trees that, at least in our San Francisco Bay Area climate, don’t need to be sprayed with copper and horticultural oil.

That being said, peaches, nectarines, plums, grapes, pears, and apples can all benefit from a dormant spray to help fight off fungal infections carried by the rain and overwintering insects.

Keep in mind that, although copper is used by organic growers, it is a heavy metal and will ultimately end up in your soil. Toxic build-ups are possible over time.

Spraying the trees

Spray on a dry day when the copper won’t be washed off by rain or diluted by fog for at least a few hours (a few days is preferable).

Mix up the liquid copper and horticultural oil in the sprayer, making sure to follow the directions carefully for both. In my case, Kelly’s horticultural oil and 27.15% copper solution called for 3 tablespoons of oil and four tablespoons of copper per gallon of water.

I used a Gilmour hose-end sprayer, available at many nurseries and hardware stores. The sprayer attaches to the end of a garden hose and mixes the water with the copper and oil solution.

Kelly’s sprayer has eight settings. The higher the number on the dial the more tablespoons of copper and oil are added per gallon of water. I used 8 tablespoons per gallon on the peach and nectarine trees and four tablespoons per gallon on the pear trees.

Exercise caution

While dormant spraying is easy enough to do yourself, it’s worth exercising caution. Contact your local extension office and try to find knowledgeable nursery-folk to make certain that you are using the proper proportions and only spraying trees that really need it.  Every time I visit the local hardware store, I am shocked and horrified at the number of chemicals available to anyone who feels like paying the price.

17 Responses to Tis the Season for Dormant Fruit Tree Sprays

  1. Sarah, your posts are always so timely. My peach tree hasn’t bloomed yet, and I have been worried about curly leaf this year, so perhaps I will go ahead with a copper and oil treatment. Although I have an Indian Free Peach, which is supposed to be resistant to curly leaf, I’m pretty sure that it occurred last year — I’m working on addressing some drainage issues in the soil where the peach tree lives, which I understand might make it more susceptible.

    • Katie, although the scientific literature doesn’t point toward this approach, Kelly swears she has had decent success with managing peach leaf curl by hand picking the curly leaves off the tree. Depending on the size and leafiness of your peach tree, this may or may not feel feasible, but it’s worth a try if your tree bursts into bloom before you get your hands on some copper and oil.

  2. I wish we had known about spraying with copper when I was growing up. We had two beautiful peach trees in our backyard which both succumbed to curly leaf.

  3. Thank you! Good to know. I’m rather “hands on” with my beloved trees, so I will try that approach!

  4. This is a great post! I am the new editor of Marin MAster Gardener’s ‘Leaflet’ newsletter to the public and I was looking for info on spraying dormant trees without using harsh chemicals. Can I use this as the basis for an article? (I can give credit at the end to the blog.) I’m actually using a product recommended to me by a nurseryman called ‘Actinovate’ and it has worked miracles, including halting/curing symptoms on my Siberian Elm, peach leaf curl AND what I can only call ‘reverse aging’ on a mature peach tree in my leachfield. I want to try and find a way to talk about it without ‘promoting it,’ per se.

    • Hi Nancy,

      I’m so glad you found our blog, and thanks for your kind words! You are welcome to draw from the article (thanks for asking!), and we hope you will. Please do give credit to Overall Gardener, and please provide a link (if online) or just type in the URL if your article will be in print. It’s great to discover the online version of your newsletter, which we found interesting and informative. We look forward to reading it in the future.


    • Hello,
      Can you publish what rate of Actinovate you used it on your Elm tree? Thanks. Nupur

  5. Do you have any advice for my beehives parked under two peach trees? I have Blighted for two years and use no oil. only copper before bloom, hand picking any curly leaves. As I am in NW Missouri, Moving my hives is bad.

    • Hi Christina:
      It sounds like you are referring to peach leaf curl, yes? Here, we are supposed to spray 3 times during the dormant season, but we did not spray at all this year, largely because our peach and nectarine are next to our chicken coop. We had peach leaf curl last year, and we controlled by hand-picking, which is easy enough on two 7′ x 6′ espalliered trees. I’m not sure how big your peach trees are.

      On the other hand, we have a plum tree near our hives. We occasionally need to spray it with copper and oil to control shot-hole fungus and kill any overwintering aphids. In this case, we waited until evening, when the bees were home, before pitch-dark, so there was still some light. Then, we draped the hive with a plastic tarp, such that there was ventilation on at least one side of the hive (we have ventilation holes drilled on the back side, and a screened bottom board). Then, we sprayed as quickly as possible, trying to be thorough, but never spraying directly at the hive. After we sprayed, we waited about half an hour before removing the tarp.

      The hive is still alive, so I’m assuming what we did worked. It’s worth noting that both copper and oil are toxic/harmful to bees, so if you have been avoiding oil but need to use it, you should go ahead and use it.

      A final note: If your hives are particularly territorial or have been bothered by animals in the evenings, you might want to wear your bee suit while spraying.

      Good luck!

  6. My peach tree is hanging over my chicken coop. How does spraying the copper affect the chickens ? Should it be avoided ? Will the birds be ok? Please let me know

    • Hi Dave–Good question! Copper is a heavy metal, and it is toxic. We have peach and nectarine trees next to our coop. We generally let the girls run around somewhere else and cover the coop with a tarp while spraying. Hope this helps!


  7. Hi! I have bought my home last summer and found a pear tree on property. I’d like to eat the fruit. It dropped quite a bit of fruit last fall.

    I had the tree trimmed in the Fall. And I’m on Cape Cod on the ocean.

    Is the tree dormant prior to flowering? Or only when it’s totally bare? I guess I’m actually asking if I can do the copper spray anytime prior to flowering, even after leaves have come.

    Any other thoughts/hints would be welcome.


    • Hi, Doug. Sorry for the very late reply. The tree is dormant after it loses its leaves and before the buds swell prior to bloom. You can do a copper spray any time during this period. You might want to check to see if your county has an agricultural extension office or website for more specific information about spraying in your climate.

  8. Nani Balakrishnan

    Hello, I read some things here not found anywhere else! I have a dwarf 2-in-1 Nectazee nectarine and a peach tree less than 6′ tall about 5 years old. I saw very little peach leaf curl 2 years ago and a lot last year in 2016 after which I learned about peach leaf curl.There were a lot of fruits that were tasty but were all very soft before ripening and turned brown inside. IN the fall, I tried to remove all the fallen leaves as much as I could. I do not use any chemicals at all in my home orchard in Roseville, CA. Although I got the copper, I was reluctant to use it. The flowers are much fewer than last year, but still remain on the tree. Much to my disappointment, I noticed the leaf curl in many of the new 1-2″ leaves already 🙁 I started pulling out those leaves but wasn’t sure if that would help, so I was very glad to read that it worked at your end!

    1. Should I continue that over the whole tree (which will be tedious) although we are having rain/storms all this week? Will it be too late if i wait until the weekend when it stops?
    2. If I spray copper after petal drop, will it be safe and effective or will the copper contaminate the fruits?
    3. Will neem oil spray now or after petal drop be an effective control of leaf curl?

    Please suggest which one or combination of methods to use to save the fruits this year.
    Thank you very much!

  9. Nani Balakrishnan

    Hello Again!

    I sure hope you’ll see my messages and offer me timely help 🙂
    On reading and seeing more pictures (after sending you my first message) I am pretty sure that my fruits must have had brown rot!! So please give me your advice on how to proceed. I would like to protect the tree and get some edible harvest as well. Appreciate your time and valuable advice!

  10. Richard Dwerlkotte

    Hi, I planted a peach tree in early Spring 2018. Six peaches developed only to be nibbled by wood rats then wholly enveloped by brown rot. I intend to spray a dormant oil / copper fungicide mixture as soon as the trees dry after recent rain. I have read here that you want to spray when tree is dormant. I also read an unreferenced online article that said that treatment for brown rot must include spraying when the tree is in bloom which seems to confound other information found online that states dormant oil will kill or damage the flowers. I would very much appreciate any clarification you can offer. Rich

    • Hi Rich:
      Yes, the spray for brown rot is an additional copper spray, performed when the tree is in bloom. And you’re right – you don’t want to use oil as a surfactant for the copper in this case. (In the dormant sprays, the oil acts on overwintering insects as well as acting as a ‘spreader sticker.’)

      I’ve actually abandoned sprays for brown rot, since it also seems to impact pollinator activity, and turned to cultural controls.

      During dormant season pruning, remove all affected spurs, twigs and branches, which are typically dead by pruning season, or those which show cankers or sap. (However, cankers or sap can also signify gummosis, a bacterial disease of peaches). Be sure to also remove any ‘fruit mummies’ left on the tree or on the ground. These are the dried, smallish (usually 1/2–1″) fruits that didn’t develop. You can do this with your hands vs your pruners. Finally, prune for good air circulation. This can be a little painful when you realize you’re removing fruiting wood, but I think it’s especially helpful.

      During the growing season, I thin the fruit when it is about 1″, such that fruits have about 1-2″ of space between them. As the fruit matures, I monitor them and remove any that show signs of mildew or mold. These two practices are especially helpful.

      Since your tree is young – and small at this point – you might try these options for cultural control and see how they work for you. In our climate, I feel like they’ve been more helpful than the sprays.

      Good luck!

Leave a Reply

Your email address will not be published. Required fields are marked *