Insects and rain move the bacteria to flowers and shoots. The rate at which bacteria move through woody tissues also slows down and cankers are formed. Infection does not usually occur unless the bacteria are washed by rain to natural openings at the base of the flower.īlossoms wilt and die about 1-2 weeks later.īacteria oozing from blossoms spreads to young green shoots.Īs the season continues and shoot growth slows and stops the shoots become progressively less susceptible to new infections. Bacteria can be moved from flower to flower by bees. Once in the flowers the bacteria multiply rapidly and, when temperatures are greater than 18 oC, can build to very high levels. Lifecycleįire blight bacteria overwinter in blighted branches and at the edge of cankers formed during the previous growing season.Īs the weather warms in spring the bacteria multiply and ooze to the surface in sticky droplets.īacteria can be transferred from the active cankers to spring blossoms by insects and rain splash. The entire tree on a susceptible rootstock can wilt and die if these areas become infected. The inner bark under the bark associated with a canker may change colour from green to brown depending on the host plant variety.Īctive cankers produce bacterial ooze. Canker blightĬankers on branches or stems appear as dark discoloured slightly sunken areas with a narrow callus ridge along the outer edge. Infected fruit gradually dries and remains attached to the branch rather than dropping. Infected fruit often exudes droplets of sticky bacterial ooze especially when the weather is warm and humid. If infected later expanding red, brown or black lesions appear. Fruit blightįruit appears small, dark and shriveled if infected when young. Shoot blight infections can expand beyond the current season’s growth into the older supporting wood, causing dark sunken cankers to form. Infected trees appear to be scorched by fire, hence the name ‘fire blight’. When the bacteria invade and kill the cambium tissue of the branch, all flowers, leaves and fruit above the girdled area die. Under favourable conditions shoot blight infections will multiply and continue to expand down the stems. Small droplets of sticky bacterial ooze can often be seen on the surface of fire blight shoots when the weather is warm and humid. The leaves and the stem on young shoot tips turn brown or black and bend over into a characteristic shape similar to the top of a shepherd’s crook or candy cane (Figure 1). Shoot blight is the most obvious symptom of fire blight and can appear one to several weeks after petal fall. Bacteria move from the flowers into the shoots. Generally the entire flower cluster becomes blighted and killed. In the early stages of infection blossoms appear water-soaked and gray-green but quickly turn brown or black. The first symptoms of fire blight can be seen in the flowers as blossom blight (Figure 2). The most typical symptom is the shepherd’s crook (Figure 1). Descriptionįire blight is a bacterial disease caused by Erwinia amylovora.įire blight can appear as different symptoms, depending on which plant parts are affected and seasonal timing. Email with a clear photo and your contact detailsĪ full list of notifiable plant pests and diseases can be found in Schedule 2 of the NSW Biosecurity Act 2015.Call the Exotic Plant Pest Hotline 1800 084 881.You can report notifiable plant pests and diseases by one of the following methods: Notifiable statusįire blight ( Erwinia amylovora) is a notifiable plant disease in NSW.Īll notifiable plant pests and diseases must be reported within 1 working day. This plant disease is a serious threat to Australia’s apple and pear industries. Fire blight ( Erwinia amylovora) is an exotic plant pest not present in Australia.
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