Battling Bugs And Blights

Blights, bugs and fungi perhaps not the most appetizing reading over a morning cup of coffee, but hopefully it’s informative reading.

Because of a few short weeks of bitter cold this past winter and a wet spring, a fist-full of diseases and critters are making themselves known.

The following are a few of the intruders:

Sycamore Anthracnose, better know as sycamore leaf and twig blight. Though this disease is no stranger to our sycamore tree population, years of constant infection are beginning to take a toll.

According to Tonie Fitzgerald, WSU area-extension agent, the winter’s severe low temperatures added extra stress to the already weakened condition of these declining trees, which are steadily losing vigor. Large and small limbs are dying back, leaves are smaller than they should be and are dropping prematurely.

The disease is caused by a fungus that attacks only sycamore or plane trees and does not spread to other kinds of trees such as maples, oaks or fruit. The fungus survives on small twigs of sycamores during the winter, infecting new leaves and shoots as they emerge in the spring. As this new growth dies, the trees struggle to produce new growth, further weakening them.

Controlling sycamore blight is possible but requires spray equipment that can reach throughout the entire tree. Fungicide sprays should be applied at bud break in early spring and repeated as the new growth expands.

Sprays applied after new growth begins are of little value. However, pruning out the dead and dying twigs and branches greatly reduces the disease. Pruning diseased tissue can be done at any time of year.

Homeowners can help alleviate stress on infected sycamores by getting plenty of water to them during the dry summer months.

Peach Leaf Curl: It’s not uncommon this spring to see thick, curled, crinkled leaves on peach trees. This disease may infect a small part of the leaf or the entire leaf. Later in the season, these distorted, colorful, puckered leaves become gray and have a powdery appearance. They then turn yellow or brown and drop.

The leaves aren’t the only part of the tree affected by this disease. The fruit may also be infected. Diseased peaches are distorted by irregular, swollen and colored areas on the skin.

Fungus spores are produced in microscopic sacs on the surface of diseased leaves. Rain, wind or birds transport the spores onto twigs and leaf buds. When the buds first swell, usually in the spring or mid- to late-winter, if temperatures are mild, the spores fall into the buds and onto the young unexpanded leaves.

Once the fungus enters the leaf, it develops rapidly through the leaf tissue. Once the infected leaves drop, new leaves are rarely infected. But it’s this premature defoliation and setting of new leaves that weakens the tree, making it susceptible to other diseases or death.

Control: Rake and destroy infected leaves. Do not compost them. Chemical sprays will not treat already infected buds. Treatment must be applied as a preventive measure during the dormant season, just before buds swell. In the Inland Northwest, a single dormant spray in February with fixed coppers (Microcop), lime sulfur, chlorothalonil (daconil 2787) ziram or bordeaux 12-12-10 will usually control peach leaf curl.

For more information on either sycamore blight disease or peach leaf curl disease, call the Master Gardener Clinic and Resource Center at 533-2048, Monday through Thursday, 9 a.m. to 1 p.m. Next week, we’ll peek into the world of a few pesky insects that torment us and invade our flowers.

, DataTimes MEMO: Phyllis Stephens is a horticultural consultant and landscape designer in Spokane.

The following fields overflowed: CREDIT = Phyllis Stephens The Spokesman-Review