There are many species of spider mites. Many are specific to a plant or family of plants; others can feed on a wide range of plant hosts.
Most spider mites feed on the underside of leaves, sucking the juices out of individual cells, leaving an appearance of tiny dots, call stippling. But there are some mites like the southern red spider mite that will feed on the surface of the leaf.
The most common spider mite may be the two-spotted spider mites. They feed on a very wide range of plants including many flowers and vegetables.
Most spider mites like hot weather and their life cycles will increase from weeks to days in hot, dry conditions. Most mites winter over as adults, emerging and laying eggs. The larvae hatch out and feeds, it only has 6 legs. Then they go through 2 nymph stages before becoming an adult, with 8 legs.
Spruce mites are a cool season mite, attacking spruce, arborvitae and junipers, as hot weather approaches their activity decreases.
Before I talk about controls, many products list spider mites on their label, and some do not. Many of these are broad-spectrum, killing more of the natural predators of the mites than mites themselves. Carbaryl, Malathion & Pyrethroids all fall into these categories. Some increase the reproduction of spider mites. Also remember, most systemic insecticides DO NOT control spider mites.
The best controls for spider mites are oils. Oils are suffocating, if an insect can’t breathe, it will die. There is no way an insect can build resistance to suffocation. Since oil is a suffocate, it is a contact killer, complete coverage is required to achieve desired results.
The absolute Best product for spider mites is the NG Horticultural Oil. This is not a dormant oil, this is a highly refined oil made from plants, so is very safe and is OMRI Listed. In hot weather, when temperatures are over 93° make your application; very early in the morning, right before dark in the evening or on an overcast day.
An organic option for control is ferti-lome / Natural Guard Spinosad Soap. The Spinosad Soap is a terrific way to treat spider mite infestations and can be used on all plants including labeled vegetables.
Another OMRI Listed, choice is ferti-lome Triple Action, which contains Neem Oil and is also a fungicide. Be careful of temperatures over 90 degrees.
During dormancy, HY Dormant Spray is more effective on overwintering adults and eggs.