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Information and Photographs by Paul Pecknold, Extension Plant Pathologist
|Fire Blight on Golden Delicious Apple||Fire Blight on Ornamental Pear "Aristocrat"|
|Fire Blight on Ornamental Pear "Aristocrat"||Fire Blight on Ornamental Pear "Aristocrat"|
Reports in the Spring of 2001 indicated a severe outbreak of fire blight in southern Indiana (especially the New Albany and Madison areas). Initial reports indicated the ornamental pear "Aristocrat" and Jonathan apple as showing epidemic blossom blight. What to do? First, DO NOT bother with pesticide spraying. There are no pesticides that will cure or prevent further spread of blight. Also, at this stage DO NOT fertilize or attempt any other cultural practices (pruning, watering) that would stimulate plant growth. You want to stop (slow) further plant growth for the remainder of the year.
If epidemic blossom blight is present, with nearly every branch having a majority of the blossom clusters affected, it is neither practical nor desirable to prune out affected blossoms. Extensive pruning of fire blighted trees will generally only result in spreading the disease and stimulate the growth of even more new, susceptible tissue. If only a "limited" number of blossoms or twigs are affected then prune out affected areas, cutting 10-12 inches below any symptoms of disease. Sterilize cutting tools between each cut by dipping them in a freshly made solution of 1 part liquid bleach added to 9 parts of water, however, be sure to rinse tools thoroughly with water before putting them away to prevent corrosion from the bleach water. Pruning shears may also be dipped in a solution of 70% denatured alcohol or 5% Lysol. No doubt some stem/limb death will occur over the summer.
In late winter, have clients/growers go in and prune out all dead tissue (dormant pruning does not require sterilization of cutting tools). If commercial apple growers are involved, also suggest dormant copper sprays and streptomycin sprays at bloom for the 2002-growing season.
Plant and Pest Digital Library and Digitally Assisted Diagnosis, Purdue University, West Lafayette, Indiana.