When is a winter dormant spray necessary for home fruit trees?
Dormant sprays can be required for deciduous fruit trees when pest damage has been observed in a tree or is known to be prevalent in an area. Where they are needed, dormant sprays are especially important because they help control certain pests at a time when coverage is easiest (no leaves) and because dormant sprays cause the least harm to beneficial insects and the environment. Dormant sprays are most effective when combined with other key cultural practices that contribute to tree health and vigor: proper planting, the right levels of soil fertility and moisture, pruning, weed control and orchard sanitation.
Horticultural oil may be applied as a dormant spray to control many pests that overwinter in deciduous fruit trees, especially scale, mites and aphids. Dormant sprays with fungicide may be required to control such diseases as peach leaf curl and shot hole. Winter spray requirements vary from one fruit tree growing region to another.
For local dormant spray guidelines, refer to your local retail fruit tree nursery and to your Cooperative Extension and Master Gardener program.
See also the question "How do I keep my fruit trees free of pests and disease?"