Fungal disease in plum tree

(Question)

please what is the treatment for fungi, the reason being that, my plum treat is full of it. thanks.

(Answer)

Thank you for contacting the Toronto Master Gardeners about how to treat the fungal infection in your plum tree.

Unfortunately, plum trees are susceptible to a couple of fungal infections: brown rot and black knot. Black knot is easily identified as it affects only the woody tissues of the tree and appears as elongated, rough black swellings or knots on small twigs and branches. Since your brief description doesn’t include that and mentions only that your tree is full of fungi, I suspect that  brown rot is the problem.

Brown rot is a common problem in plum trees and can become  severe during wet, humid weather. [We’ve had a lot of this type weather in the Toronto area this summer]. The following is a detailed description of the disease by The Connecticut Agricultural Experiment Station:  Brown rot causes blossom blights, twig blights, twig cankers, and fruit rots. Infected blossoms wilt, shrivel, and die, becoming covered with a grayish mold. Infection can then spread to the twig and form a brownish oval canker. These cankers can expand andeventually girdle the twig, causing the terminal growth to wither and die. On fruit, symptoms first appear as a small, circular brown spots that increase rapidly in size and eventually result in a soft rot of the entire fruit. Under wet, humid conditions, ash-gray, powdery tufts appear all over the surface of the fruit, a characteristic diagnostic symptom of this disease. Fruit decay is often not apparent on immature fruit but becomes obvious as fruit begin to ripen. Fruit which are wounded (by insects, mechanical injury, bird pecks, etc.) are more readily infected than unwounded fruit. Rotted fruit may fall to the ground or persist as mummies on the tree. The fungus overwinters in fruit mummies on the tree or ground and in twig cankers. In spring, the fungus produces two types of spores; one type is produced on the surface of cankers and mummied fruit on the tree and the other type is produced in mummied fruit on the ground. Both spore types can cause infection under warm, moist conditions.

The first step in managing and treating the plum tree is sanitation; you must remove infected leaves, fruit and prune any affected branches. Remove them from the area and dispose of them since they may continue to be a source of pests. Make sure that you clear everything from underneath the tree. Do not compost the leaves, etc.

Secondly, you need to maintain an open canopy in the tree to improve air movement and reduce wetness that promotes disease development. Prune the tree seasonally to keep the tree structure open.

Thirdly, you may need to use a fungicide to control the present fungal infection. In Ontario, many sulfur-containing products are available that will help to control the fungal disease. Local stores may be able to recommend specific products. Under the Ontario Pesticide bylaw, one can buy what has been approved for home gardens. [See: <www.ontario.ca/environment-and-energy/pesticides-home-lawns-and-gardens>].

By following the above steps, you should be able to successfully treat the fungal infection on your plum tree. Of course, maintaining the health of the tree through good cultural practices is the most important aspect. If you have any other questions, please let us know. Thanks.