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Twospotted Spider Mites

The two spotted spider mite is oval in shape, about 1/50 inch long and may be brown or orange-red, but a green, greenish-yellow or an almost translucent color is the most common. Spider mite development differs somewhat between species, but a typical spider mite life cycle is as follows. The life cycle is composed of the egg, the larva, two nymphal stages and the adult. The eggs are attached to fine silk webbing and hatch in approximately three days. The length of time from egg to adult varies greatly depending on temperature. Under optimum conditions (approximately 80° F), spider mites complete their development in five to twenty days. There are many overlapping generations per year. The adult female lives two to four weeks and is capable of laying several hundred eggs during her life.

Looking for spider mites: For detection of spider mites, a 10X to 15X magnifying glass is a necessity. Examine the undersides of the leaves closely for mites, cast skins and webbing. A more efficient technique is to place a sheet of white typing paper beneath the leaves and strike the foliage sharply. The mites will fall onto the paper and can be more easily observed and identified than on the green foliage.

Spider Mite Control:
Beneficial Insects: Predators are very important in regulating spider mite populations and should be protected whenever possible. Important genera include the predatory mites, Amblyseius, Metaseiulus, and Phytoseiulus; the lady beetles, Stethorus; the minute pirate bugs, Orius; the thrips, Leptothrips; and the lacewing larvae, Chrysopa.

Least Toxic Pest Control: Insecticidal soaps and oils should be carefully considered when a pesticide is required. They are effective against mites and the least toxic to people, other non-target organisms and the environment. The effectiveness of laundry soaps, washing detergents, and vegetable oils is less consistent than with chemical pesticides. Although some growers have been quite pleased with the results of non-insecticidal quality soap and oil use, some have been disappointed. Also, plant varieties differ in their susceptibility to burning induced by soaps and oils. Environmental conditions, as well as micronutrients, fertilizers, and other additives may affect a tendency to “burn” foliage. At higher rates of application, (2%), burning and stunting are more likely.

The two spotted spider mite develops a resistance to most acaricides after prolonged use. Most miticides are not effective on eggs. Therefore two or more applications of the miticide will be required at five-day intervals during the summer or seven-day intervals during the winter.

This information came from the University of Florida fact sheet: Twospotted Spider Mite, EENY150/IN307
Thomas R. Fasulo and H. A. Denmark

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This article was reviewed and updated in June 2013.

Photo Credits:
University of Florida