Pear Tree fungus - Ask Extension
Hello,
I have an issue with my pear tree. The rep at the Miller Library booth told me that you can assist.
Please see the pictures I have atta...
Knowledgebase
Pear Tree fungus #874297
Asked June 23, 2024, 2:05 PM EDT
Hello,
I have an issue with my pear tree. The rep at the Miller Library booth told me that you can assist.
Please see the pictures I have attached. My pear trees started to get these copper fungus every year for about past 2 years. Before I have never had these issues. Last year I pruned the trees close as possible and got rid of all branches etc. I sprayed early this year with copper fungus spray but it came back again. No other shrubs, plants or trees are effective. And I do not see any fungus on my pine trees, neighbors trees. I have two pears trees and both are affected.
Can you assist preventing these fungus or what ever this is?
Your assistance will be greatly appreciated.
Thanks
Yong
Howard County Maryland
Expert Response
Hello Yong,
This is a very common fungal disease called rust. (In particular, it's probably Cedar-Quince Rust, or possibly Cedar-Hawthorn Rust, since they look very similar.) The name of the disease stems from the rusty-orange color of the spores in addition to the fact that the fungus spends part of its life cycle on cedar trees (not true cedar, genus Cedrus, but Eastern Redcedar, which is actually native species of Juniper, Juniperus virginiana.) Eastern Redcedar is a very abundant native plant in Maryland, and is important to wildlife. Spores on rust-infected juniper trees can travel for a mile or more on the wind to their host plants (pear, apple, crabapple, and some other relatives), so it's not always practical to prevent infection by finding and removing nearby junipers, nor would junipers be treated with fungicide.
Once symptoms appear, fungicide sprays on the pear will not be effective for that year. Spores produced on the pear are only meant to start a new juniper infection. In spring (around April in central Maryland), spores from infected junipers drift onto pear and other hosts to start new infections there. It's at that time, early April or so, that protective sprays must be applied, and usually repeated over the course of an 8-10 week widow of time until spores finish leaving the junipers. While copper-based fungicide formulations will probably work if they are labeled for controlling rust, perhaps they didn't work in this case if not applied early enough or often enough. Rain can also interrupt any fungicide spray schedules, potentially allowing a window of opportunity for infection to occur, rendering them not completely effective.
Since fruiting pear trees are commonly afflicted by a range of pests and diseases, the routine sprays used to protect them will probably combat rust in the process. More information about the recommended care of pear trees can be found on the linked page, including the document it links to that includes pesticide recommendations. (You can choose to use organic sprays if you prefer, but some type of regular prevention spraying every year is usually necessary to preserve tree health and protect the harvest from being ruined.)
You do not need to prune off rust infections, and doing so will potentially deprive a tree of important photosynthesis capacity to be able to store energy to flower and fruit normally. Pruning could also affect branching structure, which is important to establish in young trees and then maintain as they get older. You do not want bushy growth that tends to result from excessive pruning, as this crowds leaves, making them more disease-prone, and also can reduce fruiting due to the shade the leaves cast on each other.
For now, just keep the tree's roots in good health by monitoring the trees for watering needs. Feel the soil about six inches deep in the root zone, watering well when it becomes somewhat dry to the touch at that depth. If damp when checked, watering is probably not needed. Extend the mulch circle to a wider reach around the trunk, removing any grass or weeds in that area first so they don't compete with the pear's roots. Don't pile mulch against the trunk; keep the layer flat and only about two to three inches deep, leaving a couple inches around the trunk itself free of mulch.
Miri
This is a very common fungal disease called rust. (In particular, it's probably Cedar-Quince Rust, or possibly Cedar-Hawthorn Rust, since they look very similar.) The name of the disease stems from the rusty-orange color of the spores in addition to the fact that the fungus spends part of its life cycle on cedar trees (not true cedar, genus Cedrus, but Eastern Redcedar, which is actually native species of Juniper, Juniperus virginiana.) Eastern Redcedar is a very abundant native plant in Maryland, and is important to wildlife. Spores on rust-infected juniper trees can travel for a mile or more on the wind to their host plants (pear, apple, crabapple, and some other relatives), so it's not always practical to prevent infection by finding and removing nearby junipers, nor would junipers be treated with fungicide.
Once symptoms appear, fungicide sprays on the pear will not be effective for that year. Spores produced on the pear are only meant to start a new juniper infection. In spring (around April in central Maryland), spores from infected junipers drift onto pear and other hosts to start new infections there. It's at that time, early April or so, that protective sprays must be applied, and usually repeated over the course of an 8-10 week widow of time until spores finish leaving the junipers. While copper-based fungicide formulations will probably work if they are labeled for controlling rust, perhaps they didn't work in this case if not applied early enough or often enough. Rain can also interrupt any fungicide spray schedules, potentially allowing a window of opportunity for infection to occur, rendering them not completely effective.
Since fruiting pear trees are commonly afflicted by a range of pests and diseases, the routine sprays used to protect them will probably combat rust in the process. More information about the recommended care of pear trees can be found on the linked page, including the document it links to that includes pesticide recommendations. (You can choose to use organic sprays if you prefer, but some type of regular prevention spraying every year is usually necessary to preserve tree health and protect the harvest from being ruined.)
You do not need to prune off rust infections, and doing so will potentially deprive a tree of important photosynthesis capacity to be able to store energy to flower and fruit normally. Pruning could also affect branching structure, which is important to establish in young trees and then maintain as they get older. You do not want bushy growth that tends to result from excessive pruning, as this crowds leaves, making them more disease-prone, and also can reduce fruiting due to the shade the leaves cast on each other.
For now, just keep the tree's roots in good health by monitoring the trees for watering needs. Feel the soil about six inches deep in the root zone, watering well when it becomes somewhat dry to the touch at that depth. If damp when checked, watering is probably not needed. Extend the mulch circle to a wider reach around the trunk, removing any grass or weeds in that area first so they don't compete with the pear's roots. Don't pile mulch against the trunk; keep the layer flat and only about two to three inches deep, leaving a couple inches around the trunk itself free of mulch.
Miri
