Today we will continue our pest invasion series and we will be talking about spider mites which actually are not insects.
As you know, if you live in the midwest, the heaters are on full blast and have been since last fall. Our skin is dry, our hair is crazy because of static electricity and we are drinking more water. If you think you feel dry, imagine how your plants are feeling? When the air gets dry, I swear a dinner bell we can’t hear rings, and the spider mites flock to the table. The leaves of your houseplants are the piece de resistance on the menu. Then, as if out of the blue, you start noticing the leaves of your plants getting splotchy and they may have a silvery sheen to them. Yikes. The spider mites are feeding on the juices of your plants. Most likely you will not see the mites unless you get your magnifying glass out and really look. They usually are hiding on the back of the leaves, but if they are present in large numbers, they may be on the front, back, and everywhere else.
Two-spotted spider mite
The most common mite indoors is the two-spotted spider mite, Tetranychus urticae. Let’s talk a little more about these little “buggers”. If you look closely at the bottom of this picture below, you can clearly see the two spots on the body of the mite. These spots are actually the accumulation of body waste showing through their transparent bodies. Yuck!
They are in the same class, Arachnida, as spiders. They look like insects, you say. Yes, they do, but the difference is that they have 8 legs, among other differences. The front four legs point forward and the four legs in the back face backward. And the really weird thing, the baby mites have 6 legs like insects, but on their last molt, they come out with 8. Their cone-shaped heads are called gnathostome and are between their two front legs. They have no antennae and no abdominal segments like insects. They also have no jaws but have things called stylets that come out of the mouth, called the stylophore. These stylets aren’t hollow tubes as insects have, but are like solid rods. Whereas scale, mealybugs, and aphids use those tubes to probe deep into the phloem of the plant and suck up the juices like iced tea through a straw, mites stab into the leaf surface, and as the liquid leaks out of the cells, they suck up those droplets. In the areas where the fluids drain out of the cells, those cells die and so we see the mottled or spotty appearance of the dead cells on the leaf surface. Mites kill cells, insects do not. The next three pictures show the damage mites have done to a leaf.
Webbing is an indicator
You may not notice the problem until the webbing the mites make is apparent. This webbing protects the mites and also acts as the roads they use to get around your plant. Once you see webbing, the problem is quite advanced. If you use a Swiffer or dust cloth of some sort to dust your plants, even if only a few mites are present, they can hitch a ride from one plant to the next. They may also attach to your clothes or the fur of a pet walking by and brushing against the plant. Even the small breeze we create as we walk by could help them move to the next plant. Sneaky little buggers! If you suspect a problem and think it may be mites, tap your plant over a white piece of paper and they will fall onto the paper and move. Hopefully, you catch them early before they become a huge problem.
So how do you prevent or control the mites if you have them. First of all, mites love hot dry air and reproduce faster in warmer temps. Keep your heat a bit lower, but most importantly, wash your plant often and keep the humidity as high as you can when the furnace is blasting. I like to use pebble trays under plants that are especially susceptible to mites, such as palms. Another thing I like to tell people about is heat deflector for heat vents..* I have them on most of my heat vents so that the drying air isn’t blowing right up onto my plants. I think it is important not to have air blasting directly on your plants. If the mites are allowed to get out of hand, they can completely defoliate your plant. I have seen this happen. Those are a couple of ways to prevent mites from invading your plants.
If you find that you have them, I would still take my plant to the shower or sink and really give it a good spray down to get rid of as many mites as possible. Then I would use a horticultural oil or insecticidal soap (works on mites, too) or a miticide on the plant. Remember, insecticides do not work on mites as they are not insects. ALWAYS read every label to make sure you are using the correct product for the particular problem you are dealing with.
You may also encounter cyclamen mites, Steneotarsonemus pallidus in your home. These are most often found on cyclamen and African violets. You may notice the middle of your violets are more fuzzy and the centers are tightly packed together. The leaves may also be distorted or smaller than normal. These mites, unlike spider mites, like higher humidity, so they are living where the new foliage originates where the young supple leaves are found. You would need a large magnifying glass or microscope to see these mites. Most likely you won’t see them with the naked eye. If you suspect your plants have these, it is better to get rid of them. I have known African violet growers who have thrown a large portion of their plants in the garbage because of cyclamen mites. There are chemicals that may work, though, and that decision is up to you.
I hope this post helps you identify and deal with spider mites. They aren’t easy to get rid of, so hopefully the prevention methods above help, but if you do find some, deal with them swiftly so they don’t get out of hand. Happy growing! If you have any questions, please leave it in the comments below and I will answer it to the best of my ability.
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