Plum trees should be pruned in June to ensure that they are not prone to further disease. They are susceptible to silver leaf disease, which reaches the tissue through openings in the stem. This disease is serious and should be dealt with immediately. Pruning sick plum trees will make them healthier and promote a better fruit crop.
Use sharp pruning shears on your sick plum tree and make cuts that are as clean as possible without crushing the wood, which will cause further damage.
Identify the shoots and branches that are diseased or damaged and follow them into the canopy of the where they meet healthy limbs.
Cut the sick plum tree limbs at the V-shaped place there they meet the trunk or other limbs. Cut as much of the diseased wood as possible to prevent decay-producing fungi from affecting other parts of the tree.
Sterilize your pruning shears between each cut to prevent the further spread of disease. Rinse the blades in rubbing alcohol or a 10 percent bleach solution.
Burn dead and diseased wood after removing it from the sick plum tree.
Remove some live branches from the center of the tree to increase air circulation and exposure to sunlight. This will help reduce disease infestation.