The year 2000 will probably rank as one of the most prominent disease years in recent history. Although many diseases such as anthracnose, powdery mildew, and scab reached epidemic levels in 2000, fire blight was more devastating on plants in 2000 and than in any year in recent memory. Unlike many diseases that may reach epidemic proportions, fire blight may be lethal on its host plants. I was informed of the destruction of many landscape plants due to severe fire blight infections in 2000.
Fire blight is caused by the bacterium, Erwinia amylovora.
In fact, fire blight was one of the first diseases to be attributed to bacteria. Bacteria diseases are not nearly as common as fungal diseases on our landscape plants. Under conducive conditions in the spring, bacteria populations increase quickly. Sometimes the bacterial populations attain such levels that amber droplets ooze form on overwintering holdover cankers or other infection areas. Each amber droplet may contain millions of bacterial cells.