Spider Mites - A Plant Pest
Bugs That Aren't Really Bugs
The problem with one of the worst houseplant bugs, is that they are not bugs. Spider mites are, indeed, spiders and have the 8 legs and physiology of spiders rather than the 6 legs that are typical of true insects.
Why Do I Care? To control things that are attacking our plants we need to know their life cycle and when we can have the most success attacking it. Spiders do not have a larval stage as insects do but rather one or more juvenile stages where they look and act very similar to the adult form. In the, plant attacking, spider mites, these stages are moved through very quickly in hot dry conditions. It is possible to go from adult to egg and back to adult in as little as four days. That is the key piece of information that we need to attack them successfully.
How Do I Identify Them? That depends on how good your eyesight is and where you look. They usually inhabit the underside of leaves. They are just visible to naked eye but they appear as little beige dots. A magnifying glass will reveal the eight legs and a couple of black dots on their backs. These dots are actually internal organs visible through their transparent bodies. Useless but interesting bit of information. They are sometimes called two-spotted mites because of this feature. The quickest way to identify them is by gently prodding them with a pencil point or something. They can move quite quickly, eight legs remember. If you see little beige specks and they run quickly across the leaf then you have spider mites. If you are not looking for them, then you will probably notice the damage they have done before you notice them. The leaves become filled with tiny pin holes from their feeding and this will eventually leave the leaf looking very pale and minutely freckled (picture left.) If you have really not being paying attention, then you may even get to see tiny webs between the leaves (picture below right,) with these little beige specks running back and forth along them. The plant is usually in big trouble at this point.
Best Method Of Attack? Two important pieces of knowledge. They live primarily on the underside of the leaves so any spray has to be applied, up under, to be useful. Second; remember the life cycle from above. No spray will harm the eggs. If you spray weekly, the eggs that survived will hatch, grow into adults and produce even more eggs before you spray again a week later. Spraying every 2 - 3 days for a couple of weeks, is needed to catch each batch of hatching eggs before they are capable of laying more.
What Kills Them? They adults are relatively easy to kill. Insecticidal soap by itself or you can also find it in combination with natural insecticides like pyrethrin, kills the adults quickly and safely but has no residual effect. If you can take the plant outside then a strong blast of water will work reasonably well and it will remove and webs that the spider mites had started to weave. Don’t relax, you have to repeat this in 2 or 3 days to catch the just hatching generation. The hot dry conditions inside our homes in the middle of winter are ideal for these beasts and there are no natural predators.
Spider mites have plants they prefer, (English Ivy, Hibiscus, Palms,) but in their absence they will happily feed on almost any of your houseplants. They are on your garden plants all summer as well but your plant’s good health and rapid growth combined with some natural predators, usually masks their presence.
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How Do I Identify Them? That depends on how good your eyesight is and where you look. They usually inhabit the underside of leaves. They are just visible to naked eye but they appear as little beige dots. A magnifying glass will reveal the eight legs and a couple of black dots on their backs. These dots are actually internal organs visible through their transparent bodies. Useless but interesting bit of information. They are sometimes called two-spotted mites because of this feature. The quickest way to identify them is by gently prodding them with a pencil point or something. They can move quite quickly, eight legs remember. If you see little beige specks and they run quickly across the leaf then you have spider mites. If you are not looking for them, then you will probably notice the damage they have done before you notice them. The leaves become filled with tiny pin holes from their feeding and this will eventually leave the leaf looking very pale and minutely freckled (picture left.) If you have really not being paying attention, then you may even get to see tiny webs between the leaves (picture below right,) with these little beige specks running back and forth along them. The plant is usually in big trouble at this point. 
