Last year in one of your articles you talked about rust disease on plants and as I remember, you mentioned there was something we could do in the spring to help us protect our plants against this disease, but I have forgotten. What do I do to help protect my pear tree? CG

Rust is a fungal disease that affects a variety of plants. Last year wasn’t a bad year for rust disease in our area but a few years back it seemed like it was everywhere. We just never know.

Rust disease is unique in the it migrates between two different host plants during its life cycle. For one portion of their life cycle which can last two years, junipers and cedars play host to the fungus. Then the fungus migrates to another plant for another portion of its life cycle, only to return to the junipers and cedars.

Currently, the rust disease fungus will be on the cedars and junipers but will soon be moving to their new host.

Asian pear rust is a fungal disease whose summer hosts include Bradford pears and other pear trees. Asian pear rust is a little more difficult to spot on cedars and junipers, but Cedar Apple Rust wins the prize for interesting display. Cedar Apple Rust grows galls on the hosting cedars and junipers and these galls can range in size from about 1/16^th of an inch to possibly 2 inches in diameter.

With the spring rains, these galls absorb water and begin to push out what are called telial horns. They can look like very strange Christmas decorations with these protruding orange, gelatinous horns. When the horns are in full extension, these horn covered galls can reach the size of a baseball. Asian pear rust on junipers and cedars isn’t quite as easy to spot and will require a closer visual inspection to find on the branches.

If you have a cedar or juniper with these dark brown, round galls on them, now would be a good time to remove them. However, even if you removed all of the manifestations of the disease in your yard, the fungal spores that are released can ride on the wind for up to a mile. Odds are that within that radius, there will be other cedars and junipers.

To prevent the disease from spreading to your pear or apple trees, you should begin a fungicide treatment at the point where the leaves begin to emerge and continue through April on 7–10-day intervals. Fungicides to consider would include copper hydroxide, chlorothalonil, myclobutanil, or propiconazole (use as specified on the labels). Rust disease will manifest in these tiny, brownish, spore protrusion on the leaves of the apple or pear trees. At that point in the disease life cycle, spraying will help minimize the spread, but will not cure the damaged leaves. Good luck.

You can get answers to all your gardening questions by calling the Tulsa Master Gardeners Help Line at 918-746-3701 or by emailing us at mg@tulsamastergardeners.org. Photo - Tom Ingram