Be on the look out for fire blight on apple, crabapple, pear, hawthorn, and quince. Symptoms first appear in the spring as new shoots turn black and bend downward forming a shepherd s crook." Leaves droop and turn a dark color. Individual branches may look like they were scorched by fire.
Sticky, sweet ooze may drip from infected areas when it s 65 85 degrees out and moisture levels are high. Insects may pick up bacterial cells and spread them to healthy flowers and leaves.
The most important management practice is pruning and sanitation. Erwinia amylovora, the bacterium that causes fire blight survives the winter in cankers (sunken diseased areas) and diseased shoots. Pruning when the plants are dormant can help prevent moving bacterial cells around. Also, pruning when plants are dry helps prevent bacterial spread. Prune about 12 inches below the diseased areas to avoid contaminating tools. Whenever possible, plant fire blight resistant cultivars. Commercial growers use bactericides (antibiotics or copper sulfate), but without good sanitation practices bactericides are of little use.
A great reference for more information about fire blight and other fruit tree diseases is IDEA 3 Tree Fruits Insects and Disease Management for Backyard Fruit Growers in the Midwest. You can purchase this publication through:
Extension Distribution Center
119 Printing and Publications Building
Iowa State University
Ames, Iowa 50011-3171
Telephone: (515) 294-5247
Fax: (515) 294-2945
This article originally appeared in the 6/20/2003 issue.
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