What to Do About Spider Mites

Gardening means contact with some of the creep-crawlies and bugs of the world—we’ve written before about earthworms, bees, and the various critters that you might encounter in your garden. However, there’s always more to learn and there are always new challenges to contend with. Spider mites are one such challenge. This small creatures (they’re not actual insects) are common in gardens, can damage plants, and are also easily mistaken for benign or helpful bugs. As all of this can affect the health of your garden, it helps us all to know what to do about spider mites, how to detect a spider mite infestation, and what to do to help your plants recover. So, in grand Gardzen fashion, let’s dig in!

What are Spider Mites?

As we mentioned, spider mites aren’t actually insects. Members of the class Arachnida, these creatures are more closely related to spiders and ticks than to insects—but don’t worry, they pose no direct threat to humans! Spider mites live on on plants, generally nesting on the undersides of leaves and occasionally weaving silk webs to protect their nests and eggs—hence “spider mites.” They feed by biting small holes into the leaves of the plant and sucking nutrition out.  This is where the problem starts—a large infestation of spider mites can drain the fluids out of the plant’s foliage and cause damage or even death.

Identifying Spider Mites

The first step in identifying and eliminating spider mites is proper diagnosis. Spider mites are small—less that .004 of an inch/1mm in size—and reddish or reddish brown in color, although pigmentation can vary. They look a great deal like other mite species, including their predators Phytoseiulus persimilis, so visual identification is only part of identifying a spider mite infestation. Signs of a spider mites in your garden include the following:

• Spider mites lay their transparent eggs on the bottom of leaves, and may weave fine white or transparent webs to protect both their eggs and their nest. If you see either tiny clear eggs or webbingwhen inspecting your plants, you may have spider mights.
• As the spider mites feed, they drain chlorophyll from the plant, which may leave small white dotes on the leaveswhich in turn develop into yellow or brow discoloration or spotting on the plant’s foliage or stems.
• During a spider mite infestation, you may see foliage and small stems turning brown and drying outas they are drained during the spider mites’ feeding process. This may leave to large parts of shrubs or bushes—particularly evergreens—turning brown.
• Leaves falling away from the plant unexpectedlyor out of season can be a sign of spider mite infestation, or other problems with the plant’s health.

It’s important to make an accurate diagnosis of spider mites. Not all mites are bad—some are quite helpful in keeping pests away—and knowing what causes the problem is the first step to fixing any garden issue. Speaking of which . . .

How to Deal with Spider Mites

While spider mites can cause serious damage or (in extreme cases) death in plants, there are a number of steps we gardeners can take to keep them from taking up residence in our gardens and control them if they do.  Let’s start with the proactive measures for preventing spider mites:

• Keeping plants healthyis always the first line of defense for pests and disease. Healthy and happy plants are better able to deal with pests, and may not attract them in the first place.
• Avoiding overcrowding plantsand allowing for good air circulation are two important steps in keeping spider mites—as well as mold and fungi infections—away from our gardens. Proper spacing and good air circulation reduce humidity levels and keep fresh air moving through the foliage, which in turn reduces the chance of all sorts of problems including spider mites.
• Support natural predatorsin order to keep pests away from your plants and support a healthy overall environment in and around your garden. For spider mites, these include the always helpful ladybugs and lacewings along with predatory mites like Phytoseiulus persimilis. Introducing these to your garden, supporting them while they’re there, and making them welcome year after year can help keep all sorts of unwanted guests away.

Sometimes our best efforts aren’t enough, and even though we try to prevent a problem from settling into our garden we have issues anyway. If spider mites are already infesting your plants, here are some more corrective measures you can take to make them leave:

• If spider mites are present on your plants in small numbers, spraying your plants down with a hosemay actually help knock them off the foliage and send them on their way. For most of us this is the easiest and lowest-cost away of dealing with spider mites, so it’s worth a try.
• In a similar vein, a DIY spray of 1 part rubbing alcohol and 4 parts water, mixed thoroughly and applied to all parts of the plant via a spray bottle can help eliminate spider mites by dehydrating them and their eggs. As not all plants will react well to this mix, we recommend trying it on a small area or an individual leaf and waiting a few days before treating the entire plant. If the treated part or leave reacts badly, it’s time to explore another option.
• Neem oilor a natural insecticidal soap can both be used to treat spider mites and other garden bugs and diseases. These are generally store-bought products, so use them according to the manufacturer’s directions for best results. They may also prevent other unwanted bugs from moving in, which is an added bonus.
• For infestations in trees and large shrubs, you may want to consult an arborist or tree specialistif possible. Big infestations of spider mites can be difficult to treat, and professional help may make all the difference.

As always, we recommending making use of natural solutions to any garden issue before turning to pesticides or herbicides. These chemicals can be effective but they cause more problems than they solve for not only our gardens and landscaping but for the whole world around us. Better and safer options exist, and we encourage you to use them.

Spider Mites are Manageable

Like most garden pests, spider mites might be a pain to deal with, but they’re a natural and manageable part of gardening. With a little proactive care and some effective countermeasures, you can keep your garden health even if these little visitors do come calling. Gardening is always an adventure, so consider these bugs just another learning opportunity along the way. And if you do have any secret tips or hints for dealing with spider mites, let us know either in the comments or via email. Your ideas might just make things much easier for other gardeners!