| | Fire blight is a common disease in Alberta that affects apples, crab apples, pears, mountain ash, saskatoon berries, raspberries, hawthorn, cotoneaster, plum, mayday and spirea. There are occasional outbreaks of this disease when warm, wet conditions are observed in the spring and summer.
"Fire blight is caused by the bacterium Erwinia amylovora," says Robert Spencer, irrigated and specialty crop specialist at Alberta Agriculture, Food and Rural Development's Ag-Info Centre, Stettler. "Infected leaves, flowers and shoots turn brown and shrivel, eventually develop a scorched appearance and remain attached to the plant. Blackened growth often curls in a characteristic shepherd's crook and, under moist conditions, sticky ooze may be visible on diseased tissues. Entire plants may die within two to three years of infection."
Fire blight usually appears when there is abundant rainfall and warm conditions. The disease is spread by rain-splash, insects, human contact such as pruning or through contact between plants. Plants that are excessively succulent will be more susceptible to infection.
Chemical controls are not available for fire blight. The disease is best controlled by proper sanitation and cultural practices such as:
- Prune to remove infected plant parts as soon as disease symptoms are recognized. Infected branches should be pruned 25 to 45 cm (10 to 18 inches) below the furthest margin of disease infection. Extremely diseased plants should be completely removed. All diseased tissue should be burned. Disinfect all cutting tools between each cut by dipping in a solution of household bleach (100 ml/L).
- Plant health should be maintained.
- Avoid practices that promote succulent growth such as excessive nitrogen fertility, poor soil drainage and over watering.
- Control insect pests to reduce the spread between plants; however, beneficial insects such as bees can also spread the disease.
- Plant resistant varieties. There is some variation in resistance between species, and there are some resistant varieties available.
"Fire blight is a common, but potentially destructive disease pest in Alberta," says Spencer. "All efforts should be made to control and contain its spread."
Contact:
Robert Spencer 310-FARM (3276)
Alberta Ag-Info Centre 310-FARM (3276) |
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