Spraying fruit trees to manage for pests and disease can feel like navigating a complicated maze. At the end of this article, it might still feel like that. But my hope is to help provide a reference tool that you can use to care for your trees. In addition to spraying, I'm going to cover some important pest management tools that don't involve any spraying.
To begin, the first step in managing pests and disease is to identify what pest and/or disease problems you are dealing with. While there are some very benign sprays that you can use for promoting tree health in any scenario, most sprays - even organic -should only be used if they are necessary. Spraying for prevention or treatment should be done in a targeted fashion with an idea of what problem you are preventing or treating.
Caption: Organically grown Frost peach. On this tree, I trialed Surround kaolin clay, organza fruit bags, and Clemson University fruit bags for pest insect control. You can see residual white clay on the tree's leaves, an organza bagged peach in the upper frame out of focus, and centered - a pristine peach after the Clemson bag was removed.
Tree Health
Taking steps to support tree health can be more effective than any spray regimen. Healthy trees can more easily combat disease and resist pest pressure. Some of these steps come down to choices at planting, and others relate to maintenance care. If you're planting new trees, pay close attention to these.
Choose disease resistant varieties when possible. Read about what specific diseases are common in your area, and look at varieties that are resistant to those. The more disease resistant the variety, the less you have to worry about managing for disease. Choosing to plant disease resistant varieties can save you lots of time, money and heartache. For example, you may choose apples which are resistant to scab, fireblight, and powdery mildew like Liberty, Honeycrisp, Winecrisp, Enterprise, Goldrush. For peaches, look for resistance to peach leaf curl, canker, bacterial spot and brown rot.
Choose a planting site with good sunlight. Fruit trees need a good amount of sun to be healthy. Full-sun is best, though a half day of roasting Boise summer sun may be plenty. Work with what you've got. But if you've got a lawn in full sun and your fruit trees in a shade hole on the corner of your property, you might need to rearrange your priorities. In addition to supporting tree health, sunlight equals sugar. No sun, no fruit.
Choose a planting site with good soil and drainage. Heavy clay soils hold water and don't breathe well, and can foster disease. Ideally you want a loam soil with lots of organic matter. If your whole property is heavy clay, dig a big ol hole (3 ft wide and deep) and fill it with 50% native soil and 50% good planting/raised bed soil. Then do your best to improve the soil around the hole in following years with cover cropping etc.
Give your tree adequate water. There's no hard rule on how much water your tree needs. It depends on your soil's water holding ability, rainfall, temperature. Spend time in your garden, stick your hand in the dirt, and make sure it's not real wet, or real dry.
Keep up with pruning. Make sure your tree is pruned to allow for good sunlight penetration and good air circulation in the canopy. Air and sunlight help combat disease pressure.
Feed your trees. You can mulch your trees with compost, and use organic fruit tree fertilizers to make sure your tree has adequate nutrients to grow vigorously.
Regalia spray for immune stimulation. Regalia is an organic spray derived from Japanese knotweed. This is a very benign spray that can be used throughout the season. Japanese knotweed contains botanical compounds that are directly anti-fungal and anti-microbial, and also is understood to stimulate your tree's immune system.
Organic Controls for Pests and Disease
Spraying instructions and gear. For all sprays, make sure to read the label for application rates and for instructions on proper PPE. You do not want even organic sprays, and sometimes especially organic sprays (like lime-sulfur), in or on you. In other words, you generally don't want to breathe them in or get them on your skin. Some are more benign than others, and it is important to read labels for this reason.
Most gardeners and backyard growers can get by with a simple hand pump sprayer. It's nice to have a few sprayers if you are using multiple spray types. If you have a lot of trees, particularly tall trees, or you just don't want to fiddle with hand pumping, a battery powered backpack sprayer can make things easier and more comfortable.
Dormant Oil / Horticultural Oil - the term "dormant oil" is used to refer to different types of oils that are sprayed on the tree. The oil coats the tree and suffocates or smothers the eggs of overwintering insects. Oil can also help smother the spores of some disease conditions like powdery mildew and scab. When combined with other sprays like copper, it helps them "stick" to your trees better. The thicker, or more viscous, the oil the better job it does at smothering insects. Thick oils like canola or soybean can be used when the tree is fully dormant, before buds start to open. If you're looking for canola oil spray, you might have to make your own. Lighter, mineral oil based sprays have become more popular because they are less likely to burn (like a bad sunburn) the tree's leaves if you happen to spray too late. Lighter oils can also be used during the growing season if you follow the application rates and don't spray on a hot, sunny day. I use this horticultural oil and have been happy with it. For a homemade dormant oil, you can use this recipe modified from Cornell University: mix 2 tablespoons canola oil, 1 tablespoon of baking soda, 1 teaspoon of dish soap in one gallon of water. I have't personally used that recipe, but I wouldn't hesitate to. On peaches, apricots, and cherries, spray oil at bud stage 3. On apples and pears, spray oil at from green tip to first pink / stage 4-6. (see bud stage charts below)
Copper Fungicide - Copper is one of the most important go-to organic sprays for helping to control fungal diseases, and some bacterial diseases. Copper can help control peach leaf curl, powdery mildew, fireblight, and canker. For peaches, to control peach leaf curl spray copper at bud break stage 2. If your trees have significant issues with peach leaf curl, repeat every 3 weeks for 3 total sprays. On apricots, spray once at bud break spray 3 to help control canker. To control fireblight on apples and pears, spray copper at silver tip to green tip bud stage. (see bud stage charts below)
It is best not to spray copper if you don't have known disease issues, as it may accumulate in soil over time. This is more of a concern with commercial growers who use copper concentrations much higher than what is available in products available to the home gardener, but it should still be considered. That said, many people use preventative copper sprays on peaches because they are so prone to fungal disease like peach leaf curl. This is the one I use.
Sulfur / lime sulfur. Sulfur and lime sulfur are not the same thing, but they are both important organic fungicide controls. One benefit to sulfur is that it's not understood to accumulate in soil the way copper does, and many people try to get by with just sulfur if they can. Lime sulfur is an organic control for fungal diseases including scab, peach leaf curl, and brown rot. However, lime sulfur is not sold in or shipped to Idaho. It is sold in and shipped to other states. I don't know the full story behind that, but one issue with lime sulfur is that while very safe for the environment - it is highly alkaline and will burn human tissue. It can cause blindness if you get it in your eyes. A less problematic downside, is that it will make your yard smell like rotten eggs for a couple weeks after spraying. You can get micronized sulfur, like this, in Idaho. It will help to fight fungal pathogens, it's just much less strong and effective than lime-sulfur. Adding micronized sulfur to your oil horticultural oil and copper sprays can help provide more fungicidal support. Note that apricots do not like sulfur, it's best to completely avoid using sulfur on apricots.
Neem Oil - pure neem oil is the best organic way to prevent peach borers that I am aware of. It's highly effective, but needs to be done preventatively. Peach tree borers can be a major problem in our area. They basically bore into the base of the tree, and can kill the tree rather rapidly if they get going. Borers can be effectively controlled by painting pure raw neem oil (it should be thick and spreadable like peanut butter, not like an oil that pours) on the bottom 6 inches of the tree in early spring. I've been advised to dilute it 50/50 with sesame oil on young peach trees (1-2 years old) as the young bark is more tender. I use this one from Dyna-grow.
Regalia - as mentioned above, Regalia is a pro-active disease fighter that's derived from Japanese knotweed. It helps to build up your tree's resistance to disease. I have personally had good luck with using Regalia alone to control scab on my apple trees. I spray Regalia starting at stage 4, and then roughly every 3-4 weeks for a total of about 3-4 applications. As an herbalist, I really like using a Regalia because it's probably the closest thing I've found to giving your tree a dose of herbal medicine. So far I have not seen Regalia in any local stores, but it can be found online.
Surround kaolin clay - if you have every wondered what the white residue on your organic apples (often in the hard to wash area around the stem) - it's clay! Surround is a kaolin clay product that is one of the best and most benign organic controls for pests. You spray your whole tree with it, and the ultra-fine clay creates a protective barrier against pest insects. When insects are crawling around on your tree, the clay gets in their wings, and messes with their ability to move, fly, and breathe. It does not actively kill insects, it just makes your tree a very unpleasant place for them to be. You begin using Surround at petal fall. Pollination is done, so you're not messing with bees pollinating your flowers. By keeping a coat of clay on the tiny fruits, it prevents attacks from early insects. You then reapply as need (when rain washes it off) and keep a steady coat of clay on your tree throughout the season. It works best when used on the whole tree, as insects crawl around your tree to get from fruit to fruit or leaf to leaf.
I have one season under my belt using Surround and there's some things I like about it and things I don't like. Aesthetically, I don't love it. It basically looks like you painted your tree clay-white. For stone fruits, I won't use it again as I found it too difficult to wash off the skin without tearing. Especially hard to get off fuzzy peach skin. For apples and pears, I likely will use it again. It's relatively easy to wash off apples and pears, and it beats the heck out of spraying broad-spectrum poisons. Even organic pesticides are still broad-spectrum killing agents. There is, however, another tool for preventing bug damage that I like better - read on for that.
People often wonder if Surround will interfere with photosynthesis. Research has shown that it basically does not. While it does block some light transmission, it also helps regulate the tree's temperature so it's able to respirate (an essential part of photosynthesis) more efficiently. I think about it a little like tree sunblock, which I think apples especially can benefit from here in our hot, dry summers. My favorite use of Surround isn't actually on fruit trees though. I found it very helpful in my vegetable garden on two crops - tomatoes and squash. Click here to read more.
Clemson University fruit bags - if you haven't heard of fruit bagging, it's going to sound insane at first. When the fruit is the size of a nickel, you go around and put little bags over each fruit. It definitely takes some time. It is not practical for large orchards or very tall trees. But man, when you open that bag to find a perfect peach inside - no bug damage, bird pecks, or squirrel bites and you didn't have to use any organic or conventional poisons - it feels real worth it then. Last season I experimented with a number of fruit bagging approaches - nylon "Organza" gift bags, "maggot barriers" - they're basically panty hose for apples, and Clemson fruit bags. Far and away, the winner was the Clemson bags. Organza bags are nylon aka plastic trash, and they keep out some bugs, but not all. The panty hose were a huge PITA to put on, and if you stretch them too much bugs get through. Clemson bags are paper bags with a vent to make sure the fruit doesn't rot, and a twist tie integrated into the top. They were the easiest to use, somehow the vent doesn't allow bugs in (how I don't know), and birds and squirrels didn't recognize the white bags as bounty to steal. All our peaches in Clemons bags came out pristine. Your results may vary, but I think the folks at Clemson take their peaches seriously and they really know what they're doing. They can also be used for other fruit like apples and pears, which I plan to try out this year.
Spinosad is an organic insecticide derived from a soil bacterium that is toxic to insects. Spinosad is effective on soft-bodied insects like thrips, leafminers, mites, ants, caterpillars. It is much less of a broad spectrum killer than organic insecticides like pyrethrin, and there are a number of pests that it likely won't kill. Even though Spinosad is relatively benign, I do my best to avoid using it whenever possible. Spinosad does kill bees, so it is best to avoid spraying spinosad during flowering. It is recommended to spray it in the evening when bees are the least active, as it shouldn't affect bees once it has time to dry on the tree. Spinosad is effective to control thrips, but to prevent thrip damage on fruits it must be sprayed during bloom because the thrips cause the damage in the flower stage. Thrips can cause "cat-facing" on fruits, where there are scars that look like scratches or bumps in the skin of the fruit. This doesn't compromise the fruit, other than in its aesthetic appearance. Personally, I don't spray Spinosad during bloom because killing bees to prevent cat-facing is not worth it to me. If you have small fruits showing scar marks, it's too late to spray for it - the scarring was already done for this year.
Stages of Fruit Bud Development
For apples and pears
Disease sprays, listed by disease
Apple scab. Lime-sulfur, Regalia, copper, horticultural oil. Spray oil and copper at silver tip to green tip. Spray sulfur stage 4-7. Spray Regalia starting at stage 4 every 3-4 weeks for 3-4 applications.
Fire blight. To control fireblight on apples and pears, spray copper at silver tip to green tip bud stage. Spray Regalia starting at stage 4 every 3-4 weeks for 3-4 applications. Prune out and remove fire blight infected wood as soon as possible. Removing fire blight sensitive apples and late-blooming apples from your orchard is another solution.
Peach leaf curl. Copper spray, sprayed 1-3 times at 3 week intervals starting at bud stage 2-3. Regalia, sprayed starting at stage 4 every 3-4 weeks for 3-4 applications.
Bacterial (Pseudomonas spp.) Canker - Copper spray, sprayed 1-3 times at 3 week intervals starting at bud stage 2-3. Regalia, sprayed starting at stage 4 every 3-4 weeks for 3-4 applications. Stone fruits (peaches, nectarines, apricots, plums, cherries) are prone to canker, which typically shows up as blackened areas with oozing gum or sap.
Fungal (Cytospora spp.) Canker - Copper spray, sprayed 1-3 times at 3 week intervals starting at bud stage 2-3. Regalia, sprayed starting at stage 4 every 3-4 weeks for 3-4 applications. Some suggest that lime-sulfur needs to be combined with copper for effective treatment of Fungal canker. Note: apricots do not like sulfur, avoid using sulfur on apricots.
Bacterial spot - Copper spray, sprayed 1-3 times at 3 week intervals starting at bud stage 2-3.
Brown rot - Lime sulfur may help control brown rot, but many do not believe there is any effective organic control for brown rot. Chemical fungicides may be used, but one of the most effective tools is removing trees that are prone to brown rot.
Pest sprays, listed by pest
Thrips - Horticultural oil, sprayed at bud stage 2 on peaches, apricots, and cherries and sprayed at green tip to first pink / stage 4-6 on apples and pears. Spinosad sprayed at bloom to prevent catface scarring. (if you're willing to kill some bees)
Peach tree borers - Pure Neem Oil, painted on the bottom 6 inches of your tree in early spring. Dilute 50/50 with sesame oil for young peach trees (1-2 years old).
Mites, caterpillars, ants, leafminers, apple weevils. Horticultural oil, Surround, Spinosad, Clemson fruit bags. See instructions above.
Earwigs, Stinkbugs. Surround, Clemson fruit bags. Chickens or ducks patrolling under your trees.
Coddling moth. Horticultural Oil, Surround, Spinosad, Clemson fruit bags.
Apple maggot. Horticultural Oil, Surround, Spinosad, Clemson fruit bags.
Oriental fruit moth. Horticultural Oil, Surround, Spinosad, Clemson fruit bags.
Spray Schedule
It would be great if there was a calendar date for each spray. But sprays need to be timed according to the tree's growth stages, which varies each year with weather. To accurately time sprays, it's best to spend time in your garden paying attention to fruit bud development, and take notes each year so you have a rough idea of what to expect for next year.
Here is an example of my personal orchard notes from 2023, to give a frame of reference. I do not recommend using these dates as when to spray - pay attention to your trees each season. I'm also not a terribly reliable garden note-taker. For example, I did not note the dates when I sprayed Surround or when I put on Clemson fruit bags, though that should have been approximately early May last year.
2.11.23. Apple and pear buds dormant, peach buds starting to swell.
Sprayed horticultural oil on apples, pears, peaches, apricots, cherries.
3.3.23. Peaches at stage 2, apricots at stage 3, cherries stage 3. Sprayed copper and horticultural oil on apricots, peaches, cherries.
3.27.23. 2nd copper spray on peaches
4.11.23 apricots at first bloom
4.12.23 sprayed KDL*, snow and 30 degrees night time low temp
4.18.23 sprayed apricots and peaches with KDL. 26 degrees night time low temp.
*KDL is a potassium dextrose lactose spray to prevent frost damage, unrelated to pest and disease.
4.22.23. 3rd copper spray on peaches.
4.27.23. Apples and pears stage 3-4 / half inch green. Sprayed horticultural oil and Regalia on apples and pears.
6.12.23. Seeing apple weevil damage on apples. Sprayed horticultural oil and Regalia on apples.
Random notes on using Surround for tomatoes and squash.
A lot of people here are familiar with the "August slump" in tomato ripening. You might start getting ripe tomatoes in mid-July, but then the summer heat really starts to bake and we get those 100 degree days that can go on for weeks. Often tomatoes "stall out" and you've got vines loaded with not-ripe fruit, which then start to ripen all at once in September and then it starts to freeze. This has something to do with the tomato plants not being able to ripen as well in heat over 80 degrees. So last year, when we had a trellis loaded with New Girl (my new favorite tomato) and various heirlooms that stalled out in August, I started spraying them with Surround. Within a few days, they started ripening to completion again. It seems they just needed a little sunblock. I learned about this practice from reading about commercial tomato growers using Surround this way.
The past several years I've had terrible problems with squash bugs absolutely hammering my summer squash, zucchini, butternut and delicata squash plants. So last year when they started showing up I started hosing down my squash plants with Surround clay. I found that I had to apply it once or twice a week to keep the squash bugs off the plants, which was more than I would have liked. But we did get plenty of good squash and the bugs didn't fully kill any of the plants. I'm still looking for a better solution for squash bugs, and I'm personally not willing to regularly use organic broad spectrum insecticides like pyrethrin. For now, Surround is the best I have found that fits that bill.
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