Take a close look at many evergreens in the area - from junipers, to arborvitaes, to Cypress - and you’ll see varying degrees of brownish patches. More than likely, they are infested with spider mites.
If ignored, these critters can ravage a myriad of evergreens, and lately I’ve seen an uptick in listener questions about Cypress trees displaying evidence of this little pest. In most cases, I can tell spider mites are the culprits because the plants are described as incurring a slow browning in clumps.
Spider mites also frequently damage lantana and azaleas. On lantana, spider mite damage gives leaves a mottled look, and the bloom clusters seem somewhat deformed. With azaleas, the damage also produces a mottled look on the top side of leaves, and sometimes you’ll see faint webs on the leaves in morning dew.
This year, however, it seems spider mite damage has been more intense on junipers, arborvitaes and Cypress than on lantana and azaleas.
I’m guessing they seem so bad this year because most people don’t know how to test for spider mites, and they’re not using proper control measures. That might be due, in part, to many people moving to our region from northern states, where evergreens never experience spider mites. So, they ignore the tell-tale signs until the damage is widespread.
So, the first step is to determine if spider mites are really the problem. Since they are so small, there’s little chance that the average homeowner will see them with the naked eye, so you should perform the “white paper test.” Hold a blank sheet of paper under a leaf cluster where there’s a bit of damage and tap the cluster downward towards the paper. If you’ve got spider mites, a bevy of the tiny critters will fall to the paper and start scampering everywhere.
Now, you have to treat with a specific product. And this is why it is best to test for spider mites before you spray. I call it simple environmental responsibility. If you don’t have spider mites, you’d be needlessly spraying chemicals, not treating for other possible causes, and wasting money to boot.
The best control measure, in my opinion, is a liquid systemic insecticide with acephate as the active ingredient. “Acephate” will be printed in very tiny letters on the product label. I prefer that you stay away from imidacloprid-based systemics, for a couple of reasons. First, acephate provides a bit of contact-kill in addition to a systemic control - imidacloprid does not. Second, research has shown that imidacloprid-based controls are a severe threat the bee population. I agree that all systemic insecticides can adversely affect bees. However, acephate has been around a lot longer than imidacloprid, and talk of bee colony collapse increased after the introduction of imidacloprid. So, play it safe in this instance.
There are also some all-natural or organic products designed to control spider mites. Neem oil is one, and some products like Mite-X from Bonide contain a combination of natural cottonseed, clove and garlic oils. Spinosad has also been known to help control these critters. The downside to using natural products, however, is the need to repeat applications several times to get total control.