Two-spotted spider mites overwinter as adult females in protected places. The overwintering mites are bright orange; the summer forms are usually cream to green in color with two dark spots on their backs. Eggs are deposited on the lower surface of the leaves when they feed. The length of their life cycle varies greatly, but in warm weather it may only require two weeks to age from egg to adult. This is why mite populations may build up very quickly.
The spruce spider mite is fast becoming the number one pest of ornamental plants. It is a pest of all species of spruce and also attacks arborvitae, junipers, and larch. On spruce, the mites feed on sap to the point that the needles lose their bright green color and become gray or brown.
The spruce spider mite overwinters as an orange-colored egg on the needles and twigs of the host plant. The eggs hatch early in the spring, and the mites throughout the summer are dark green to dark brown in color. Feeding and reproduction continue throughout the summer. A generation of spruce spider mites may occur in about 17 days; they, too, can build up to a very high population during summer.
Signs and Symptoms:
If plant foliage begins to acquire an off-green color and mites are
suspected, a foliage check can be made to determine if mites are present.
To do this, take a piece of white paper, hold it under a branch suspected
to have mites, and strike or shake the branch against the paper. Mites
will fall onto the paper if present. The mites are only about 1/50 of
an inch in diameter.
Cultural Practices for Control:
Normally, all evergreens will have small populations of mites. If several
mites are seen, then management procedures need to be considered. Cool,
humid and rainy weather will normally hold mite development and numbers
down to a non-damaging level. Hot, dry weather is ideal for development.
On small plants, hosing with a garden hose will often knock mites and
eggs from the foliage. Good pruning practices are an effective method
of keeping mite populations low. Older brown branches should be thinned
out each fall or spring.
Pro-Care Practices for Control:
Healthy, vigorous plants will usually resist mite damage, but hot, dry
summers are ideal for high mite populations. Deep root fertilization
and mite control will help keep damage to a minimum. The Pro Care tree
care program includes these services.
The Pro-Care staff is always ready to assist you with your trees and shrubs. Please call if we may provide any information to enhance your landscape's health or appearance.