There are myriad species of spider mites in North America. These spider mites are less than ½ millimeter in length and generally too small to easily spot with the naked eye. Gardeners are usually alerted to their presence by the tiny yellow or white spots they leave behind as they feed on the plant tissue. If spider mites are present in large enough numbers, there may be so many spots on a leaf that it looks yellow or bronzed. Once this happens, the leaf usually drops. Luckily for most gardeners, mites rarely gather in numbers that large and they are easy to get rid of if they do.
Spray your plants with a stiff spray from a hose once weekly. Spider mites do not firmly attach themselves to your plant and are easily knocked off.
Purchase and release predatory mites like Phytoseiulus spp., Amblyseius spp. or Metaseiulus spp. into your garden. However, not every predatory mite eats every sort of plant mite and not all of them are suited for every type of climate. In order to release predatory mites effectively, consult a professional first.
Spray heavily infested woody or perennial plants with a horticultural or dormant oil in fall or spring. Mix a 3 to 4 percent solution of horticultural or dormant oil and spray it on the plant tissue until all of the plant tissue is well coated (the spray works by contact) but not dripping. One application will kill most of the mites and any eggs that they have laid.