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Homeowners often want to know why their ornamental pear trees have yellow to brown spots on the leaves. These leaf spots are caused by cedar-hawthorn rust. It is a fungal disease similar to cedar apple rust that occurs on crabapples, but a different organism causes it. This disease is passed from junipers to the pears in the spring and from the pears to the junipers in the summer. Instead of spots on the leaves, junipers have roundish brown growths that look a little like human brains on their needles. After the spring rains, the fungus on the junipers will be covered in orange tentacle-like growths. Spores are released from these growths, called spore horns, and then infect pear trees creating brown or orange spots on the leaves.
This disease doesn’t generally do long-term harm to pears trees. Raking up the infected leaves in the fall and disposing of them can also help break the disease cycle. If chemical control is desired, it must be done in April and May. Spray with Ferti-lome F-Stop anytime the orange gelatinous galls are present on the junipers. This generally happens after rain.
*Please read and follow all label instructions when applying chemicals.