Spider mites are very tiny bugs that resemble spiders (if you see them magnified), as they are in the arachnid family. They have eight legs but no antennae. They lay their eggs on the undersides of plants' leaves. While there are several species of these, nearly all of them are harmful to your plants. While industrial, commercial farmers must often turn to powerful pesticides to try to do away with a spider mite problem, more localized, home gardeners can and should turn to more organic means of protecting their plants from this invasive, harmful pest.
You can recognize these garden pests before you actually see them--remember, they are no bigger than a tiny dot to the naked eye--if you start to notice thin webbing on your plants. Do not assume, if you start to see webbing, that this is from a benign spider.
If you see this webbing, immediately look to see if you notice any brown or graying leaves on what should be a healthy plant. If you do, get out a magnifying glass and look for mobile red, greenish, and brown "dots" on your plants--those would be the mites.
(You can see these insects with your naked eye, but you can't make out any details at all.) If you have plants with leaves encased in webbing, these pests have taken "ownership" of that plant.
For those who desire an organic solution to these harmful garden pests, know that their predators are ladybugs and predatory mites of the Phytoseiidae family, and lacewings. You can purchase packages of these helpful insects and dump them onto your plants.
Even if you don't have any infestation now you could still place them around your plants to ward off or be a preventative against the spider mite.
These mites thrive in dry, arid conditions. Their predators tend to like more wet, moist conditions. So, if you choose to use natural predators to kill off the garden pests, supplement them with gentle leaf-misting of your infected plants from the underside-up.
You can also use a powerful blast of water to disrupt the life-cycle of the mite, for this strong water jet can blast their eggs off of the undersides of your plants' leaves. You should not blast jets of water like this if you have recently put natural predators into your plants, however, for you could also blast them away.
Safer, organic pesticides to spray:
Insecticidal Soap (use carefully as it can burn the leaves of tender foliage if applied in the hottest part of the Summer)BioNeemBonide Hot Pepper WaxConcern Pesticidal Spray OilHorticultural Oil (for Summer use)Dormant oil--this is used specifically to kill harmful mites, bugs, and so on that go after woody-stemmed plants and trees; these oils are intended to kill the garden pests and their larvae just when they are awakening from their long Winter's nap. Therefore, dormant oil is to be used in the Winter, not during the rest of the year.
These safer pesticides can still be mildly poisonous to bees, fish, birds, and even people, so use them judiciously and in accordance with their labels' instructions.
You can also make use of sulfur powder to kill spider mites and this is an especially good choice if you also find that you have fungus infections, since sulfur powder readily kills both fungus and spider mites.
Be wary of spider mites as you garden. If you keep your plants nicely watered this will make them less attractive to these mites. However, make sure you don't drown your plants' roots, for them you are asking for harmful nematodes, fungi, and "root rot". Top of spider mites page
The plant should watered once a week, but not until they are soaked through. The water should be able to drain out any excess.