Rust on Juniper and Asian Pear trees - Ask Extension
Rust has been affecting my Juniper and Asian Pear trees the past 2 years. Please advise how to eradicate the rust as it is killing my trees and ruinin...
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Rust on Juniper and Asian Pear trees #880301
Asked August 05, 2024, 4:23 PM EDT
Rust has been affecting my Juniper and Asian Pear trees the past 2 years. Please advise how to eradicate the rust as it is killing my trees and ruining the fruits on the Asian Pear tree. The bark on the pear tree is splitting and the leaves are curling and dropping off. Altogether there are 3 pine trees, and 1 pear tree in close proximity to each other. 3 trees are more than 9 feet tall
If possible I would like a non chemical or green solution. Thank you.
Prince George's County Maryland
Expert Response
The symptoms pictured are not those of a rust fungus, which look quite different, especially on the Juniper host. (Rust fungus also does not infect the plants pictured, which are a Hinoki Cypress and a Dwarf Alberta Spruce, not juniper or pine.)
The browning on the Dwarf Alberta Spruce are too drastic for the plant to recover from. It's hard to tell at this advanced stage what the cause was, but it likely involved prior outbreaks of spruce spider mites. We can't see evidence of bagworms currently, though prior issues with them and/or a needle cast or canker infection can't be ruled-out either. (The linked page focuses on Colorado blue spruce, but those diseases can infect other spruces as well.)
The dried older needles on the Hinoki are likely due to drought or other environmental stress. We see what looks like plastic over top of part of the root zone...if so, it should be removed, as it interferes with water absorption and oxygenation of the root zone, both of which can stress or kill roots, which in turn will result in foliage dieback and shedding. Has the tree been monitored for watering needs during dry weather? Last year and this summer (so far) have had significant drought, and evergreens don't usually wilt or show indication of stress and damage until foliage is lost and branches die back. Foliage lost on older wood will not regrow; they only produce new growth from the younger tips of the branches.
We can't see enough of the pear tree in the photos to make a diagnosis. Can you please share pictures of its symptoms? Pear can contract fungal rust infections, but they also are vulnerable to several other pests and diseases. Our Growing Apple and Pear Trees web page includes information about typical ailments. Pesticides can't cure any existing diseases, but their use as preventative measures starting in spring each year (and continuing into the summer in most cases) can help to protect tree health as well as preserve the harvest. Organic pesticides can be selected if you prefer, though overall they tend to be less effective (and may require more sprays per year) than conventional pesticide formulations. The link to Virginia Tech's pest management guide on the page above goes into detail about what products can be used for certain pests/diseases.
Splitting bark is generally not a good sign, though sometimes it can occur simply due to rapid tree growth or a prior lightning strike. If it results from dying sapwood underneath the bark, then no intervention is possible and the tree might succumb to wood decay. Pear trees can drop leaves prior to autumn if they are drought stressed, if root damage has occurred, and if heavily infected (earlier this year) with a disease like powdery mildew. We did receive multiple questions earlier this summer about defoliating flowering pear trees from, among other causes, mildew outbreaks. On pear, a powdery mildew infection doesn't always look as blatantly powder-coated as infected leaves can look on other plants.
Has the pear been monitored for watering needs as well?
Miri
The browning on the Dwarf Alberta Spruce are too drastic for the plant to recover from. It's hard to tell at this advanced stage what the cause was, but it likely involved prior outbreaks of spruce spider mites. We can't see evidence of bagworms currently, though prior issues with them and/or a needle cast or canker infection can't be ruled-out either. (The linked page focuses on Colorado blue spruce, but those diseases can infect other spruces as well.)
The dried older needles on the Hinoki are likely due to drought or other environmental stress. We see what looks like plastic over top of part of the root zone...if so, it should be removed, as it interferes with water absorption and oxygenation of the root zone, both of which can stress or kill roots, which in turn will result in foliage dieback and shedding. Has the tree been monitored for watering needs during dry weather? Last year and this summer (so far) have had significant drought, and evergreens don't usually wilt or show indication of stress and damage until foliage is lost and branches die back. Foliage lost on older wood will not regrow; they only produce new growth from the younger tips of the branches.
We can't see enough of the pear tree in the photos to make a diagnosis. Can you please share pictures of its symptoms? Pear can contract fungal rust infections, but they also are vulnerable to several other pests and diseases. Our Growing Apple and Pear Trees web page includes information about typical ailments. Pesticides can't cure any existing diseases, but their use as preventative measures starting in spring each year (and continuing into the summer in most cases) can help to protect tree health as well as preserve the harvest. Organic pesticides can be selected if you prefer, though overall they tend to be less effective (and may require more sprays per year) than conventional pesticide formulations. The link to Virginia Tech's pest management guide on the page above goes into detail about what products can be used for certain pests/diseases.
Splitting bark is generally not a good sign, though sometimes it can occur simply due to rapid tree growth or a prior lightning strike. If it results from dying sapwood underneath the bark, then no intervention is possible and the tree might succumb to wood decay. Pear trees can drop leaves prior to autumn if they are drought stressed, if root damage has occurred, and if heavily infected (earlier this year) with a disease like powdery mildew. We did receive multiple questions earlier this summer about defoliating flowering pear trees from, among other causes, mildew outbreaks. On pear, a powdery mildew infection doesn't always look as blatantly powder-coated as infected leaves can look on other plants.
Has the pear been monitored for watering needs as well?
Miri
