Ask Henry!

Spider mites are pests that can be controlled

Reader Vicki worries about spider mites: “Spider mites! Run away! Run away! I don't have them, but how can I avoid getting them? And how can I get rid of them with natural methods? Other indoor bugs?”

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Well, Vicki, the best prevention is to have healthy plants, and that means growing them in conditions they like. Know if your houseplants want indirect light (most do) or a bright windowsill. Very dark places are stressful for most plants.

This Crown of Thorns plant is about 100 years old and thrives in a sunny window

Spider mites thrive in dry conditions, so keep your plants watered regularly (once a week is good for most) and add some humidity to the air. Place pots on saucers of small stones to which you’ve added  a little water. As the water evaporates it adds some moisture to the air near them; the pebbles keep the plants from sucking up water and developing root rot.

Spider mites are so small you can barely see them with the naked eye. They are not true insects (which have 6 legs and 3 body sections), but are arachnids, like spiders. They have 8 legs, and only one body section. They are about the size of the dot at the end of this sentence.

You can recognize spider mites by the damage they do: they pierce leaves and suck out juices, discoloring the leaves. They will first discolor the underside of leaves, and may produce webbing. Soon whole leaves will die, and unless you act fast, you can lose your Momma’s best African violet! Spider mites can produce hundreds of eggs in no time!

Outdoors they have natural enemies that keep numbers in check – ladybugs, for example will eat them – but indoors there are no predatory insects, and you really can’t add them to the house.

So what to do? Start by carefully removing any affected leaves and placing them in a plastic bag. Discard in the household trash. You should also wash the entire plant, even leaves that seem to be free of this pest. The spray attachment in the kitchen sink is good for this, and you can contain the soil with a layer of aluminum foil so you can turn the plant upside down or sideways to spray it.

Phaelanopsis orchids are rarely infested with spider mites

If you have spider mites you can also spray them with a mild soap solution. Safer Soap is a brand-name soap for treating plants that is safe for organic gardeners. Basically what it does is dissolve fats in the skin of the bugs, causing them to dehydrate and die. Get a one-quart spray bottle, dilute the solution, and spray the plant, including both sides of each leaf.

There are many chemical sprays that will kill spider mites, but I won’t use them. I don’t want to breathe in the fumes or get the poisons on my skin. But if you visit with your plants regularly and watch for problems, you can nip any problems in the bud. Good luck!

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