Suspected Quince Rust on Apple tree - Ask Extension
Hello, we moved in 2 years ago and have a lovely (slightly neglected) apple tree. Not sure what variety. We had almost no apples the first year, then ...
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Suspected Quince Rust on Apple tree #873434
Asked June 17, 2024, 12:18 PM EDT
Hello, we moved in 2 years ago and have a lovely (slightly neglected) apple tree. Not sure what variety. We had almost no apples the first year, then a decent yet dark spotted here and there crop last year (not sure what diagnosis it should have gotten). I did some pruning over winter in an effort to gradually get it to a healthier less crowded state. I just noticed this (see pics). I think it is Quince Rust. We have a few acres but no jupider/cedar on our property I believe but a lot of happy variety of mushrooms on our grounds, and some sort of fungus was brought in on the mulch we ordered last year.
My questions:
Is this Quince Rust?
What can I do for this years crop?
How should I handle things this fall, over winter, and in the spring to try to minimize it and help my tree be happy and healthy?
I tend toward organic but understand it doesn't always work well enough so am open to whatever may be needed. Please advise on how to eat fruit at harvest time to minimize consumption of chemicals if they are needed.
Any/All advice is greatly appreciated!
Thank you!
Frederick County Maryland
Expert Response
This is indeed a rust infection (both the foliage yellow-orange spotting and the fruit spores). Rust is very common on apples and their relatives (crabapples, pears, hawthorns, serviceberries, and others). Spores produced by rust-infected junipers, the other host plant required for this fungus to complete its life cycle, can blow into an area from a mile or more away, so it's hard to say where the infection is originating. Our wild redcedar (a type of juniper) is quite abundant in natural areas, and valuable for wildlife, so the pool of plants capable of harboring the fungus is large.
Once symptoms appear, either on foliage or fruit, it's too late to intervene for that year. You can trim off infected fruits if you prefer, and if you can reach them, but it's not necessary. Fungicide use can help to prevent new infections when applied to healthy growth in spring, but they cannot cure existing disease. Sprays would need to cover the entire canopy, as being thorough with applications is the only way many pest and disease preventative treatments work well, and repeated as directed on the product label (intervals can vary) in order to over an overall 8-10-week period when the spores are dispersing from junipers and moving onto the apple hosts. This will also likely coincide with flowering, during which spraying must pause to avoid risking pollinator harm. (Fungicides, even though they do not target insects, can potentially harm insects and other organisms.)
Apple trees are among several high-maintenance fruit tree types for our region, simply because they are vulnerable to a range of pests and diseases, plus require routine care (pruning, for example) to maintain an airy canopy that lets in enough light and air circulation to promote good harvest yield and overall tree health. Our Growing Apple and Pear Trees page is a good starting point for learning about what issues tend to arise and how to prevent them. A link is included on that page for a pesticide use guide published (and updated regularly) by Virginia Tech, and while you can opt to use organic formulations or conventional ones, some degree of pesticide use is generally necessary to support tree vigor and productivity. You can of course opt to not spray at all, but just be aware that this may mean the occasional loss of part or most of a harvest in a year with heavy pest or disease pressure, and/or branch dieback if an outbreak is severe (like Fire Blight infection).
Pesticides labeled for use on fruit trees take into account that the treated fruits will be consumed. (For this reason, do not use a product, even if its active ingredients are the same, that is not labeled for use on edible plants.) The product will give a timeframe during which sprays should stop to allow the residues time to break down or become non-hazardous. Sometimes this is as brief as the day before harvest; sometimes it might be days or weeks prior to harvest. It depends on the chemicals involved, and the pesticide label will mention this. It could be called a "preharvest interval, or PHI, or something similarly worded. Always rinse produce well before consumption or cooking, even if it was treated with only organic pesticides or no pesticides.
This fall/winter, rake-up and dispose of (don't compost) any debris like foliage or aborted fruit dropped by the tree. (Actually, collect any fallen fruit promptly, any time of year they drop, so they don't harbor pathogens, pests, or attract wasps, raccoons, etc.)
Any tree, fruiting or otherwise, should ideally have any turfgrass or weeds growing around its trunk base removed. The soil can be protected from erosion and weed growth with mulch instead. This not only reduces root competition for the tree (at least a little), but also helps to shield it from accidental injury from mowers, weed-whackers, lawn herbicide use, and other factors. Trunk injuries or damage can be fatal if they break through the bark and cause enough damage to the sapwood or allow wood decay to set in. Keep mulch in a flat layer (2-3 inches deep is plenty) and do not cover the trunk base or root flare. Other than monitoring the tree for watering needs (drought stress could impact flower bud production for next year's blooms and fruit), which would be routine summer and autumn care, nothing else needs to be done at this point. Our Fruit Plant Care page has more general information about watering, fertilizing, mulching, pruning, and more.
Miri
Once symptoms appear, either on foliage or fruit, it's too late to intervene for that year. You can trim off infected fruits if you prefer, and if you can reach them, but it's not necessary. Fungicide use can help to prevent new infections when applied to healthy growth in spring, but they cannot cure existing disease. Sprays would need to cover the entire canopy, as being thorough with applications is the only way many pest and disease preventative treatments work well, and repeated as directed on the product label (intervals can vary) in order to over an overall 8-10-week period when the spores are dispersing from junipers and moving onto the apple hosts. This will also likely coincide with flowering, during which spraying must pause to avoid risking pollinator harm. (Fungicides, even though they do not target insects, can potentially harm insects and other organisms.)
Apple trees are among several high-maintenance fruit tree types for our region, simply because they are vulnerable to a range of pests and diseases, plus require routine care (pruning, for example) to maintain an airy canopy that lets in enough light and air circulation to promote good harvest yield and overall tree health. Our Growing Apple and Pear Trees page is a good starting point for learning about what issues tend to arise and how to prevent them. A link is included on that page for a pesticide use guide published (and updated regularly) by Virginia Tech, and while you can opt to use organic formulations or conventional ones, some degree of pesticide use is generally necessary to support tree vigor and productivity. You can of course opt to not spray at all, but just be aware that this may mean the occasional loss of part or most of a harvest in a year with heavy pest or disease pressure, and/or branch dieback if an outbreak is severe (like Fire Blight infection).
Pesticides labeled for use on fruit trees take into account that the treated fruits will be consumed. (For this reason, do not use a product, even if its active ingredients are the same, that is not labeled for use on edible plants.) The product will give a timeframe during which sprays should stop to allow the residues time to break down or become non-hazardous. Sometimes this is as brief as the day before harvest; sometimes it might be days or weeks prior to harvest. It depends on the chemicals involved, and the pesticide label will mention this. It could be called a "preharvest interval, or PHI, or something similarly worded. Always rinse produce well before consumption or cooking, even if it was treated with only organic pesticides or no pesticides.
This fall/winter, rake-up and dispose of (don't compost) any debris like foliage or aborted fruit dropped by the tree. (Actually, collect any fallen fruit promptly, any time of year they drop, so they don't harbor pathogens, pests, or attract wasps, raccoons, etc.)
Any tree, fruiting or otherwise, should ideally have any turfgrass or weeds growing around its trunk base removed. The soil can be protected from erosion and weed growth with mulch instead. This not only reduces root competition for the tree (at least a little), but also helps to shield it from accidental injury from mowers, weed-whackers, lawn herbicide use, and other factors. Trunk injuries or damage can be fatal if they break through the bark and cause enough damage to the sapwood or allow wood decay to set in. Keep mulch in a flat layer (2-3 inches deep is plenty) and do not cover the trunk base or root flare. Other than monitoring the tree for watering needs (drought stress could impact flower bud production for next year's blooms and fruit), which would be routine summer and autumn care, nothing else needs to be done at this point. Our Fruit Plant Care page has more general information about watering, fertilizing, mulching, pruning, and more.
Miri
