I remember last year the leaves on my Bradford pear were covered with these strange looking orange growths. How can I prevent that this year? AR

What you are describing is a fungal disease called rust. A couple of years ago it seemed like rust disease was everywhere. Last year, not so much. But rather than wait and see, there are some strategies you can use to minimize its impact on your tree.

Rust diseases are interesting in that they migrate between two different host plants in their life cycle. Cedars and junipers play host to the disease during one portion of this life cycle and this portion may last two years. In your case, the Bradford pear hosts the disease for another portion of its life cycle. Right now, the fungal disease is found on cedars and junipers, and it is about time for them to begin the process of migrating to your Bradford pear.

Asian pear rust is the one that affects Bradford Pears. It is fairly small and hard to detect on cedars and junipers which makes it difficult to treat. But the most impressive manifestation of rust disease occurs with Cedar Apple Rust. Cedar Apple Rust takes the shape of a gall on cedars and junipers. These galls can range in size from about 1/16^th of an inch to two inches in diameter. When spring rains come, the galls absorb the rainwater and push out what are called telial horns. These horns are gelatinous and orange giving the impression of perhaps very strange Christmas tree decorations. Eventually, these horn covered galls might reach the size of a baseball. If you have a cedar or juniper that has these dark brown round balls on them, now would be a good time to remove before they start to push out these horns. If you are not able to remove the galls before the orange gelatin shows itself, go ahead and remove them to help minimize the spread of the fungal spores.

Removing all evidence of the disease from your cedars or junipers isn’t always enough to prevent the co-hosting plants from transferring these fungal spores to your susceptible plants because the spores can ride the wind for up to a mile.

To help protect your Bradford Pear or other susceptible plants you should begin a fungicide treatment from the point when leaves start to emerge through April on 7–10-day intervals. Appropriate fungicides include copper fungicide, chlorothalonil, myclobutanil, or propiconazole (use as specified on the labels). Cedars and junipers can be treated with the same fungicides in late June through July. Ultimately, rust disease will not prove fatal to your tree as it will grow new leaves to replace the damaged ones.

A variety of fruit trees are susceptible to rust disease including apples and pears. These trees have slightly different needs, and you can find a fruit tree spraying schedule in the Fruits, Nuts, and Berries section of our Lawn and Garden Help page on our website (www.tulsamastergardeners.org). 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: Joseph OBrien, USDA Forest Service, Bugwood.org