Prevention

• Prevention is the first step in keeping your trees free of pests and disease. Make sure your tree has room to grow and has good air circulation. Pruning trees properly helps air circulation and allows trees to control diseases. Water properly, don't over or under water. This stresses trees, contributes to the growth of shallow roots, and makes trees less resistant to pests and diseases. The right fertilization for each species is also important to keep a tree healthy and less prone to problems. Learn about different pests and diseases that may target your species of trees. When adding trees to the landscape, choose a hardier species, one that resists illnesses.
  
  

Pests

• If you are dealing with a small-scale infestation you can handpick or prune pests like tent caterpillars or bag worms. Traps and barriers are other ways to get rid of pests. Paint a thick coat of grease on the base of a tree as a barrier to stop aphids and ants. Paint it on the trunks of apple trees to prevent moths. Hang yellow flypaper in trees to trap white flies. Introduce beneficial insects like lacewings and ladybugs. They control scale, aphids, caterpillars, mites and other pests. Use insecticidal soap and horticultural oils to kill soft-bodied pests.
  
  

Diseases

• Prune diseased or misshaped branches throughout the year, even in the winter. Discard diseased wood immediately and don't let it over-winter on the ground. Wash your tools in hot soapy water afterward. The use of compost tea can eliminate some root and leaf diseases. Most fungal diseases, if caught early, can be controlled with fungicide containing copper. If you're not certain of the kind of problems your tree has, check with your local cooperative extension office.