Could 2002 be a repeat of 2001 for fire blight? We are again hearing reports of blossom and twig blight showing up in southern Indiana. Initial reports indicate both Bartlett and ornamental pear along with apples and crabapples, are showing epidemic blossom and twig blight.

What to do? First, DO NOT bother with pesticide (streptomycin and copper) spraying. There are no pesticides that will cure or prevent further spread of blight. (Note: the one exception to this is the commercial growers' use of streptomycin after petal fall following hailstorm or heavy wind damage. This "hail spray" should be made within 18 to 24 hours after the start of the storm, even if the foliage is not completely dry.)

Secondly, DO NOT over fertilize or attempt any other cultural practices that will stimulate plant growth. Growers should use management systems that promote early cessation of tree growth without adversely affecting tree vigor. Excess vigor is an important component of orchard risk for fire blight.

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 stimulating 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 2003 growing season.

Story Resources

Fire Blight
(Photo by Paul Pecknold)

Blossom Blight
(Photo by Paul Pecknold)

Shoot Blight
(Photo by Dan Egel)