Bacterial oozing out from the stem of an infected shoot Limb and trunk blight Infected shoots form an "inverted J" or a shepherds' crook at the tipįigure 4-157. Fire blight bacteria also move through the vascular tissue of the tree from a canker into the shoot resulting in similar symptoms.įigure 4-155. Usually the shoot tip is the first part affected, and occasionally the base of the shoot is the primary infection point. Dead leaves often cling to the shoot throughout the growing season and into winter. Eventually, infected leaves turn brown starting with the tissue along the midvein. Bacterial ooze along the midvein of infected leaves and the stem of infected shoot is also common (Figure 4-157). Initial leaf symptoms appear as brown or black discolouration along the petiole and midvein, while the rest of the leaf tissue remains green. Apple and pear trees with several severely infected shoots appear scorched by fire (Figure 4-156). The infected shoots form an "inverted J" or a shepherds' crook at the tip (Figure 4-155) - often the first symptoms are observed several weeks after bloom. As the bacteria move down the shoot, stem tissues become discoloured and shriveled. The bacteria move 15-30 cm or more in the shoot within a few days after infection. Injuries on leaves and shoots caused by sand blasting, wind whipping or hail provide an entrance for the bacteria into the susceptible tissue. Shoot blight symptoms are observed throughout the spring and summer seasons, especially when fire blight is present in the orchard in infected blossoms, other blighted shoots and overwintering cankers. Shoot blight develops very quickly once infection takes place. Infected shoots first appear water-soaked but quickly turn brown or black. Succulent shoots and suckers (water sprouts) can also become infected resulting in shoot blight. Infected blooms first appear water soaked and later begin to wilt, shrivel and turn brown or black Shoot blight If the spur on a main branch or the trunk becomes infected, the disease can move from the spur into the trunk or branch eventually developing into a canker which girdles the branch or limb.įigure 4-154. Once blooms are infected, blossom blight frequently remains attached to the tree allowing the disease to progress into the flower stem and then into the spur. Pollinating insects visiting contaminated flowers spread the disease to non-infected flowers. Infected blooms first appear water soaked and later begin to wilt, shrivel and turn brown or black (Figure 4-154). Blossom blightīlossom blight is observed in the spring when flowers are infected. Severely infected trees with fire blight appear to be "scorched" by fire Symptomsįire blight attacks many different parts of the tree, and fire blight symptoms are often referred to the part of the tree attacked - blossom, shoot, fruit, limb and trunk, and collar or rootstock blight. Fire blight has become a serious problem in high density apple plantings that contain new susceptible varieties and dwarfing rootstocks (Figure 4-153).įigure 4-153. The pathogen has caused most damage in southwestern Ontario, where, in some years, whole orchard blocks have been destroyed due to severe infections. amylovora is found in most areas of the province where apples are grown. Raspberry can be infected by fire blight bacteria, but the raspberry strain cannot infect apple, pear or ornamental plants. The host plants include quince, crab apple, hawthorn, cotoneaster, mountain ash and firethorn. The disease is caused by a bacterium, Erwinia amylovora (Burrill), which infects hosts in the Rosaeceae family. *NOTE: Soap-Shield, as used in this recommendation, may cause russetting of Golden Delicious and similar susceptible apple varieties.Ĭurled Stem end is a typical sign of fire blight, whichĭamages apples, pears and some ornamentals.Fire blight is a serious disease causing considerable damage and economic losses in apple and pear. We recommend Green Guard™ Plant Growth Enhancer and Soap-Shield ® Flowable Liquid Copper Fungicide*. You can also control blight by spraying a copper soap product at silver tip and bud break, and repeat at 3- to 5-day intervals as needed, up to petal fall. Spray every 7-10 days at a rate of 1/2-3/4 cups per gallon. Use a harpin protein-based product as a preventive spray during bud break. Disinfect pruning tool between cuts by dipping in 10% solution of liquid bleach to avoid spreading disease. Solutions:Ĭut off infected twigs and branches 12" below the dead area. The downward curled twig tip is characteristic of fire blight. Fire blight usually attacks blossoms, but infection and dieback of new shoots are common (see photo). Can cause severe damage to apple and pear trees.
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