Keep it Green, by Michael Womack
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Saturday, June 9, 2001
Fire blight season is reaching its peak
Have you seen blackening of your ornamental pear tree branches? If so, you're not alone. Many Coastal Bend ornamental pear trees have been dying back from the tips of their branches. The problem we're seeing this year is called fire blight, and it can affect both ornamental and fruiting pear trees as well as apples and roses.
Fire blight is caused by the bacteria that attacks the blossoms or flowers and then moves up the branches. Infected branches appear to have been burnt from the tip back. Flowers and leaves will turn brown and wilt, the stem will blacken rapidly and sometimes curl.
Severe cases may include discolored or oozing cankers on the branches. Severe infection can also result in death of the tree or rose bush.
In the Coastal Bend, late April through June is prime fire blight season.
Easy prey
Fire blight is easily spread by different circumstances. Rain can splash bacteria from one plant to another.
Migratory insects like aphids can also carry the bacteria from plant to plant, and birds and other animals can also transfer the disease. Even the unsuspecting gardener can actually spread the disease during pruning or watering.
A number of bactericides have been developed; most are sprays containing streptomycin (Agri-strepTM). These should be applied every five days beginning at first bloom. Up to three sprays can be applied. If streptomycin is not available, KocideTM or other copper fungicides may be used. Always follow label instructions.
By this time of year, the sprays may not be your best line of defense.
Pruning out fire blight-damaged branches is your best bet. This practice should be used at the first sign of blight. Cuts should be made a minimum of six to eight inches below the diseased area.
Sterilize sheers
It is imperative that you sterilize your pruning shears with a 10% chlorine bleach solution after each cut.
Making multiple cuts even within the same tree can spread the bacteria if it is on your clippers. Despite popular belief, alcohol does not sterilize your clippers; always use the bleach solution.
Because the bacteria are so easily transmitted, use extreme care when disposing of infected plant material. Diseased branches should never be left in the yard since the bacteria could be spread to other roses or trees. Always burn branches or discard in the trash.
Although there is no cure for fire blight at this time, you can control it before it gets out of hand.
Understanding how it spreads and fixing the problem quickly will help you keep from getting burned by this bacterial blight.
Michael Womack is a horticulturist with the Texas Agricultural Extension Service. Got a question? Michael Womack will answer landscape and gardening questions. Call 886-4648, category 3025 to record your question. Write Keep It Green, Corpus Christi Caller-Times, P.O. Box 9136, Corpus Christi, TX 78469 or email wm-womack@tamu.edu
2000 Caller-Times Publishing
Company, a Scripps Howard newspaper. All
rights reserved.
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