Spider Mites -
Clemson University, USDA Cooperative Extension Sarah Holden, Missoula County Extension
Slide Series, www.ipmimages.org
DESCRIPTION: Mites are not insects, although in agricultural contexts they are often discussed with insects for convenience. They are more closely related to spiders than insects. Most insects have three pairs of legs, and three major body parts, whereas mites have two body regions (cephalothorax and abdomen) and can have two, three or four pairs of legs. Many adult insects have wings, but mites never do. Mites are extremely numerous and are found in many kinds of habitats. Their small size makes them difficult to detect, identify, and monitor. The mites that attack fruit trees in the United States fall mainly into two groups: spider mites (Tetranychidae) and rust mites (Eriophyidae).
LIFE CYCLE: Mites prefer warm temperatures and low humidity. Two-spotted spider mite generations are completed in as little as 10 days at high temperatures (>80° F.). Other spider mites exhibit similar cycles.
CONTROLS: Spider mites, especially the two-spotted spider mite, are often very difficult to control with synthetic chemicals. High levels of resistance have developed in many populations.
Cultural: Spider mites overwinter on leaves, trash, and weeds on the ground and in plant crevices, so sanitation measures are important.
Providing adequate water for plant growth needs is also important in managing spider mites. Drought and fluctuating wet/dry soil conditions can stress plants in a manner that can cause spider mite populations to increase. Excessive nitrogen fertilization can enhance mite populations.
Mechanical: Overhead watering - and purposeful hosing of plants with water in a garden setting - can dislodge and kill many spider mites.
Biological: Several organisms prey on spider mites in field settings; minute pirate bugs and predatory species of mites are among the most important.
Chemical: Dormant oil sprays on deciduous species.