Bonsai Pests: Spider Mites
If you notice a fine webbing between your bonsai plant leaves you may have spider mites. Outdoor bonsai such as Juniper are more susceptible to this than indoor bonsai. Spider mites can be seen with the naked eye. Inspect the web to see if you see movement. They will look like very tiny spiders or microspiders as I like to call them.
Why they are bad for your bonsai
Spider mites feed off of your bonsai using their tiny mouthparts to suck out the plant cell contents. You may notice white or yellow areas in your foliage as a result. Leaves may fall off as a result of the damage. Your bonsai may lose its color, have its growth stunted, or die as a result of the damage if there are a significant amount of mites.
Spider mites hatch from eggs laid on the bonsai. They generally hatch into larva within the first 3-7 days after being deposited onto your bonsai.
Carefully inspect any new bonsai purchases for mites by looking at the tops and bottoms of their leaves. They are about the size of a period on a typewriter and can be introduced from contaminated soil as well.
If you would like to control the situation naturally, introducing predator insects such as ladybugs, lacewings, and predatory mites are your best solution.
If you go the pesticide route, make sure you get a miticide. Insecticides that aren't specifically miticides don't work very well on spider mites.
Alternative to chemical pesticides
For a more natural method you can try this miticide recipe that uses household items.
Spider mites can be detrimental to your bonsai, but if caught early the damage will be minimal.
Written by David Mello 6/22/07