Fire Blight

Fire blight announces itself in spring through scorched, blackened shoots that look as though they've been burned; in some cases, an entire young tree collapses at the graft union without showing canopy symptoms first. On apple and pear, you'll notice wilted flowers and shoots with a distinctive shepherd's crook appearance, and close inspection reveals cankers near the base of trunks that are dark, water-soaked, and purplish. The bacterium Erwinia amylovora enters through open flowers (which remain vulnerable for 1 to 3 days), fresh wounds, and growing shoot tips. Temperature above 65°F coupled with rain or high humidity during bloom creates the infection window.

Fire blight can kill young trees outright and severely damage bearing orchards, making prevention and rapid response your critical management tools. Choose resistant rootstocks (Geneva series G. 11, 30, 41, 65, and others) and resistant cultivars when establishing new plantings. At the first sign of blight, remove all infected material by cutting well into healthy wood, sterilizing tools in a 10% bleach solution between every cut, and never combine pruning and blight removal in the same season. When conditions favor infection, copper and other registered bactericides applied at bloom help reduce the risk, and some growth regulators like Apogee on apple show promise for early-season applications.