Now what is black Knot disease? If we concentrate on the name of the disease we can easily figure out that the disease is a type of knot like structure which is black in color. In more scientific terms the black knot disease is a fungal disease which forms knot like swellings in the region of axial bud of the plants. This disease is common in those areas where the practice of regular cutting and pruning is not carried out. This disease becomes increasingly dangerous for the plants during each growing season unless effective control is done by you. This disease has the power to stunt or kill a tree. The Black knot disease can infect a variety of fruit trees for example Japanese, American and even Japanese varieties. So you do not think that if you have a different variety it will be resistant to this disease.
Symptoms of this disease:
The black knot fungus normally affects the branches of the plants which it hosts. Seldom has it affected the main trunk of the tree. Normally the infections originate in the younger growth. Once the twigs get infected then they show brown swellings that ultimately rip open as they expand. In spring these knots are olive green in color but in late summer it becomes black in color. These Knots grow in size during the favorable period and completely encircle the twigs of the plants. This hampers the growth of the plants the proliferation of new twigs and leaves thus affecting photosynthesis adversely. This weakens the plant further. During this period the Black knots turn hard and brittle. During the second year the Black knot fungus dies and then it successes by another fungal species which urns these knots pink in color during the summer season. The entire tree is gradually weakened due to this disease and then it dies a slow death. So it is essential to control and eradicate this disease.
Causative organism and control of the disease:
The causal organism of Black Knot disease is the Fungus Dibotryon morbosum. This fungus grows and then it produces ascospores which then germinate on the surface of green twigs. When these twigs remain wet for a long time then the ascospores attack the twigs and then remain wet for a long time.
Control:
Planting resistant varieties is one of the methods to control the disease. Plant the new trees in the areas which are free from black rot disease. Remove all the wild plums and cheery trees which are the potentials of the disease infection. Prune the infected twigs and then burn them
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