One thing that I have noticed throughout the years in bonsai is that trends seems to come and go with each season. In some years, the summers are nice and hot which the pines and junipers love. Some years are a bit milder, like this year, allowing the deciduous trees a chance to excel. There also seems to be cycles on the more negative side. Ever notice how one year you deal with one weed in the garden and the next year it’s a completely different weed that you have never seen before? It seems to happen to me a lot. The same is true with insects and diseases. One year I battle a disease, the next it’s some new pest. A few years ago, it was an invasion of the Marmorated Stink Bug, and just two years ago the Ash White Fly. Luckily, neither was of much importance to my bonsai. This year and old foe has reared his ugly head in my garden with a voracious appetite. The positively evil Spider Mite.
Spider mites and I go back quite a few years. Whenever I would get my big black pine ready for a show, it would seem to get attacked at the most inopportune time by spider mites. And any attack on a conifer means that you are going to take two to three years to switch out the damaged foliage for new. The damage may be mostly visual, but it certainly is unsightly. Arghhhh! The challenge for me is that mites are so insidious. They always sneak up on me and before you know it, I have a full-blown epidemic. This year they are back and I think the early warm weather we had opened the door; hence the purpose of this article. I want to save you the heartache. This year they decimated a prize Engelmann Spruce and it will take me a few years to rebuild it. More on that later.
I need to make one thing clear before we go any further. There must be no mercy when it comes to spider mites. There is no learning to get along and coexist. Only total annihilation will work. Here are a few statistics to drive the point home. There are several varieties of Spider Mites, which are members of the spider family, but we mostly deal with the red, or two-spotted, spider mite. A female is able to lay up to 20 eggs a day. These will hatch in three days, and can be sexually active by the fifth day. So, if females live two to four weeks, they can lay over 500 eggs each and mite population explodes. This means that before you know it, they have destroyed a tree, at least for that season. They can, and do, kill bonsai. This is not just cosmetic damages. So, no fooling around. We are fortunate in that our wet climate keeps them relatively at bay, naturally.
Take a look at Photo 1. This is the leaf of a Skimmia plant in my back yard. It shows the tell-tale signs of spider mite infestation. Stippling of the leaves which make them look pale and dull.
Photo 2 is an Engelmann Spruce and you can see how the color (Chlorophyll) has been literally sucked right out of it. No chlorophyll, no photosynthesis, no tree. Notice also the light webbing, demonstrating the mite’s link to spiders.
Photo 3 is a Douglas Fir from this spring. I have never had them attack a fir before and they went after both of my Doug Figs with abandon. Though not shown, the first tree they went after was an Asian Pear. Go figure. I guess they decided they liked both pizza AND ice These photos also show how the mites sneak up on me. There are not any big holes or wilting foliage to notice. The foliage just slowly changes color over time, and since I have that tinge of color blindness, I don’t always notice right away. And since it has been years since I dealt with mites on my bonsai, it’s not really on my radar. Well, it is now. I seem to sort of scratch my head, hmmm, those leaves are changing color, wonder what that could be. Duh! So, on we go. A few years ago I wrote about lacebugs on azaleas and the damage looks very similar to mites.
So how do we confirm the presence of spider mites? It’s very simple and easy. You may all know this too, so forgive me if I am boring you. We are getting to the solution soon. Take a white sheet of paper (your hand will also do). Hold it under the tree and tap the branches a few times. You will get some detritus landing on the sheet, and probably some small specs. If those small specs are moving, you have mites. If nothing is moving, use your finger to swipe the specs across the page. If there is a smear, then they are alive and well. Rather than being the size of pinhead, they are more like a pinpoint, so very hard to see the body with the naked eye. Photo 4 nicely shows their color, shape, and webbing on a cherry tree. A full-on infestation.
So, if you have made it this far, your reward is near. Spider Mites are one of the few things that systemic chemicals like Imidacloprid with not take care of. Of course, the best defense against any insect or disease is a healthy tree. The spruce that was attacked was definitely weak after last year. You can go online and find all kinds of so-called natural remedies for mites. The problem is the most of them are dealing with landscape plants that have a much higher tolerance than our bonsai. I liken our bonsai to the fighter jets that my dad used to repair. Fighter jets live on the edge and push the boundaries of existence every day. They are regularly called to push to the limits and that is what we do with growing gargantuan trees in incredibly tiny pots.
The trees natural defenses are more limited, so we have to go the extra bit to protect them. I have tried things like Neem oil in the past to almost zero effect. Trying to blast them off with water just means that they are going to go hop onto another tree.
One thing that I have found very, very effective, as in one hundred percent, is Bifen. Never heard of it? Boon put me on to it and it has been rock-solid for mites. Bifenthrin is a pyrethroid insecticide, as in a synthetic version of the chemicals found in Chrysanthemum flowers. It was originally a termiticide, and I get mine online at pest control sources like, Do My Own Pest Control. You are not going to find this at the big box stores. I just follow the directions for spraying on the label. It’s a lot milder solution than an organophosphates like Orthene/Acephate, which I find damages new, tender growth.
There is, however, a caveat to any mite solution. Remember how we talked about the rapid reproductive cycle of mites? That means that they can relatively quickly adapt to any chemical solution. To combat that, we have to act quickly and thoroughly. It also means that it’s a good idea to rotate your insecticide after only a couple of uses. So if you don’t knock them out after two or three applications, you may have to switch to something else to be effective. I have had good luck because the infestations have been isolated to certain trees in any one season, thank goodness, and I have been able to eliminate the entire problem quickly.
You have to stay on it when you start. The development cycle of the bugs is very quick. After hatching they go through several intermediate stages called instars, in which they molt into a new body. Miticides are usually able to only attack adults, eggs, or certain stages of the instars, but not all. This means spraying regularly on a roughly 7-10 day interval so that you are able to stop the cycle, then finish them off before they mature enough to start a new cycle. I am not yet sophisticated enough to tank mix both an adulticide and ovacide together, to do it in one operation. That would require a lot of research and is beyond my scope. But maybe one of you can do that and share. I know that Mirai is using this approach. Good luck and keep an eye out for that little speckling on the leaves.