Attack of the Spider Mites
Ever noticed tiny silk webs on the leaves of your indoor plants? You may have just assumed they were spider webs, but they may not be. They may be the webs of spider mites.
The difference is important because spiders (order Araneae) are generally good for your plants – they don’t hurt the plants and eat things that do. But spider mites (order Acari) are bad for your plants. They feed on the plant, sucking the life out. And if their webs get out of control, they can encapsulate plant entirely. Kinda impressive for bugs smaller than the period at the end of this sentence.
I’ve got a lot of tropical plants in the house, which are particularly susceptible to spider mites. My lovely wife shot some video of them with a great magnifying lens. Warning: this video will make your skin crawl. Watch it fullscreen for maximum creepiness.
How to know if you’ve got ’em: Tiny webs and yellowing leaves. Sometimes you can see them in bright light – they’re tiny, but quick.
What to do: Spider mites generally aren’t a chuck-the-plant kind of problem, but they are damaging and require vigilance. Here are a few things I’ve used to keep them in check.
- Hands. When you’re tending your garden, if you notice the webs, just reach out and wipe them away to keep them from getting established. Don’t worry, spider mites can’t hurt you, but use a paper towel you can toss or a cloth you can wash so that you don’t inadvertently spread them to other plants.
- Sprays. Most pesticides don’t work very well on spider mites. Some are so harsh they can hurt the leaves, which kind of defeats the point. Worse, some insecticides can make a spider mite infestation worse, because they can kill off predatory insects.
If you’re going to spray, go for a horticultural oil spray or use Neem if you can stand the smell (I can’t). I’ve had some luck using sprays that contain Pyrethrum, which is a poison derived from Chrysanthemums. Be sure to test any spray on one plant before using it on all of them, just in case there’s a bad reaction. And generally it’s better to spray at night when it’s cool and the leaves are out of direct sunlight.
- Predators. I just tried this for the first time last week. The idea is, introduce another mite that eats spider mites, but does not spin webs or eat plants. Seems like a good idea. Unfortunately, I can’t say that it worked. I’ve been looking at the leaves under magnification all week and see no sign of the “good” mites. Maybe I just got a bad batch. I may try again. Either way, this is really only a solution if you have a ton of plants like me. It’s not worth it for a couple of houseplants.
The best thing you can do is make your environment inhospitable. Spider mites like hot, dry air, so mist your plants with plain old water frequently. The misting also makes the webbing easier to see – so wipe it off when you see it. And if you have a plant with a particularly bad outbreak, isolate it so it doesn’t spread.
Sorry for any nightmares that video causes.
Gardeners: Have you found any techniques to be particularly effective against spider mites? Please share.