![]() Dormant pruning to remove overwintering infections helps reduce inoculum for the next season. PruningĮliminate fire blight infections by pruning out diseased branches. Unfortunately, little choice exists among the hawthorn species, which tend to be highly susceptible. ![]() Most cultivars of crabapple sold in nurseries are resistant to fire blight. koidzumii Santa Cruz Prostrata, San Jose hybrid and Shawnee hybrid firethorn also show resistance to this bacterial disease. Several species of cotoneaster - including Cotoneaster adpressus, C. Bradford pear trees are moderately resistant to the disease. Ornamental pear cultivars that are highly susceptible to fire blight include Aristocrat, Autumn Blaze,Capital, Fauriei and Redspire. Most pear cultivars are susceptible, but the following cultivars show some resistance: Kieffer, Seckel, Starking Delicious, Moonglow, Magness and Harrow Delight. Arkansas Black, Red Delicious, Empire and Liberty are moderately resistant and usually do not require special treatment for fire blight. Golden Delicious, Redfree, Winesap and York apples are also susceptible to fire blight and usually require control when conditions are favorable for infection. One of the best ways to avoid fire blight is to avoid planting cultivars that are susceptible.Īpple cultivars that are the most highly susceptible are Gala, Jonathan, Lodi, York, Suncrisp, Braeburn, Fuji, Granny Smith and Mutsu. Control Cultivar selectionįire blight is one of the most difficult diseases to control. ![]() Because of the high sugar content of this ooze, infected limbs and cankered areas often develop a sooty black overgrowth of fungi. A sticky ooze containing billions of bacterial cells often develops in the region of these cankers in the spring and early summer, especially during wet weather. Cankered areas do not penetrate deeply into the wood. In either case, the infected area will become discolored and superficially sunken. The bacteria can colonize natural openings in the bark, such as lenticels, and areas where the bark has been wounded from pruning cuts, hail damage or mechanical damage or it can move systemically through the tissues of the plant from infected blossoms or shoots. Cankersįire blight cankers of various sizes can develop on twigs, limbs and even the trunks of trees. Spur infection of fire blight kills leaves and shoots. Tender shoots infected with fire blight have the typical "shepherd's crook" appearance. In either case, the dead leaves remain attached to the dried shoots. Apple leaves and shoots turn a rusty brown color in pears, these parts turn black (Figure 3). These infections often kill a foot or more of the terminal growth. When infected, the tender tips wilt, die and assume a characteristic shepherd’s-crook appearance (Figure 2). The succulent new shoot growth also is susceptible to bacterial infection in the spring and early summer. Infected blossoms turn brown and die, usually with the flower parts remaining attached. Bacteria multiply rapidly in the blossom nectar and infect the blossoms through natural openings called nectaries. This is partly because of their attractiveness to insects, which carry the bacteria from the cankers. The blossoms on susceptible trees are usually the first plant parts to become infected in the spring. Symptoms and plant parts attacked Blossom blight Careless pruning practices may also spread the bacteria. The bacteria are usually spread from the cankers by insects and by wind-blown rain. The bacteria commonly overwinter in cankers (sunken diseased areas) on the tree, which produce a sticky exudate in early spring (Figure 1). The arrow points to a fire blight canker on a large limb.įire blight is a bacterial disease affecting apple, crabapple, pear, hawthorn, pyracantha (firethorn) and related species.
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