Fire Blight Disease

Fire blight, also known as erwinia amylovora, can cause serious problems for owners of apple and pear species. Fire blight can also cause problems for other members of the Rosaceae family, including crab apple, flowering pear, hawthorn, quince, and mountain ash.

What Is Fire Blight?

Fire blight is a disease that is caused by a bacterium. The warmth of spring and the high moisture content in the air encourage the bacteria to grow and multiply. When the wind begins to pick up, the pollinators of the fire blight bacteria are carried to blossoms, new shoots, and the existing wounds of at-risk species. When infected, the bacteria spreads down through the shoot of the plant, causing tissue damage. In some cases, the bacteria can kill the plant entirely.

Identifying Fire Blight

Fire blight is fairly easy to identify on plants. New growth and flowers will often appear wilted or shriveled, usually with a dark brown or black color. In fact, fire blight gets its name from the way the disease appears in plants. The color and texture appears much as if the leaves of the plant had been scorched by fire. Often times, the physical appearance of the disease will resemble the letter “J” in shape.

Controlling and Treating Fire Blight

If infected shoots of a plant become infected with fire blight, they should be removed immediately. This is done by making the cut at least 12 inches below the area in which the blight appears. Dip the pruning shears into isopropyl alcohol between cuts, so as to avoid spreading the fire blight to other areas of the plant. Heavy pruning should be avoided in the spring time, when new shoots are forming. New shoots are especially susceptible to fire blight.

To spray to protect from fire blight, the antibiotic streptomycin mixed with water at a ratio of one teaspoon antibiotic to one gallon water should be used. The application of the spray should begin when about 20 percent of the blossoms have begun to open. Spraying should take place at five-day intervals and should always be reapplied after rain. While spraying will not help an already infected plant, spraying regularly until the petals fall can be a highly effective way to prevent fire blight.

One of the best ways of controlling fire blight is to plant resistant cultivators to begin with. Fire blight-resistant varieties of apples include ‘Liberty’, ‘Freedom’, and ‘Enterprise,’ while pear varieties include ‘Warren’, ‘Moonglow’, ‘Orient’, and ‘Ayers’. Though there is no guarantee that resistant species will not have problems with fire blight, it can significantly reduce the likelihood fire blight will develop.