Mites are minute, plant-feeding arachnids that feed on chlorophyll, the pigment that gives plants their lovely green color. By removing chlorophyll, mites can cause plant foliage to appear bleached or bronzed. Because mites reproduce rapidly, damage to healthy foliage can occur within a relatively short period.
One sign your plants might have mites (before a lot of damage is done) is webbing on and between leaves. A particularly damaging mite is the twospotted spider mite (Tetranychus urticae), which affects numerous species of broad-leaf trees and shrubs. Hot dry weather seems to increase mite populations, and drought-stressed trees are more likely to be attacked.
Keeping plants sufficiently healthy, hydrated and mulched, and being careful not to over-fertilize is the best protection against infestation. Monitoring to identify mites early and treating appropriately will more than pay off by keeping harmful mite populations in check. Predatory mites can be very effective as biological control agents and should be considered part of an integrated pest management program.