Fire blight hits pome fruit trees


Q. My apple tree has an issue. Many leaves are turning brown and dying. I’ve been spraying fruit tree spray, but the issue continues to worsen. Please help.

Rick from Beloit

A. This spring was fast and furious. Many say we went directly from winter to summer. During this quick spring, the conditions were perfect for the development of fire blight. This is a bacterial disease that infects pome fruits – that’s apples, pears and crabapples. The spring conditions this year were very warm with lots of moisture from rain, high humidity and dew.

The first infection starts when the trees bloom. The disease is spread by pollinators, rain splashing or by humans when pruning the tree. The bacteria overwinters on fruit from the previous year or on other living parts of trees.

The disease is easy to identify on apples, crabapples and pears. The tips of shoots start to turn brown, then to black and the leaves stay on the twig. The tip of the infected twig will bend down, making what will appear to be a hook shape at the end. The disease seems to appear out of nowhere as the leaves begin to look “burned” on the tips. Ornamental pears get this disease as well, but it is not as noticeable to most homeowners until they really start looking at the tree for signs of infection.

Most likely, what you are spraying is a fungicide, combined with an insecticide. Since this disease is bacterial, your spray will not remedy the situation. But you are not alone. This hot, continually wet and terribly humid weather makes fire blight even worse for all apple and pear trees.

There are some best-management practices which can reduce future infections. Prune out all infected branches past the dead leaves. Generally, this is 4 inches past any infected leaves. For bacterial diseases, pruners should be sanitized between cuts.

In general, good sanitation practice in the home orchard will help reduce infections. Clean up all plant debris at the end of the season. Keep up with pruning to allow good air circulation and sunlight penetration into the canopy of the tree. More details are available on our OSU Extension Factsheet at: http://go.osu.edu/fireblight

Eric Barrett is OSU Extension educator for agriculture and natural resources in Mahoning County. Call the office plant and pest clinic at 330-533-5538 to submit your questions. Regular clinic hours are 9 a.m. to noon Mondays and Thursdays.

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