Learn How to Fight Spider Mites

by Matt Gibson

Got spider mites in your garden or on your houseplants, and looking for options to control them? Spider mites are one of the more common pests found in gardens. These pests also affect houseplants and indoor garden setups, and not just outdoor plants. The tiny spiders, which are just about the size of the period at the end of this sentence, can quickly cause a lot of damage. If you have a greenhouse, be on alert—spider mites are known to be especially destructive to greenhouse projects.

Spider mites are not actually insects, but instead are arachnids—spiders, belonging to the same family as ticks and scorpions. Mites form colonies on the underside of leaves. They tear into a plant by piercing the leaves and sucking out the juices until the leaves turn yellow or fall off the plant entirely.

Spider mites thrive in hot, dry areas and can overtake plants swiftly. They can be so destructive and quick to spread because small infestations become large populations very quickly. Spider mites are especially common in areas where insecticides have been used extensively. While insecticides can be used with great success to kill off garden pests, doing so can also effectively kill off the common enemies of certain vermin—such as spider mites. Using insecticide to wipe out the pest population has the potential to harm other insects that are beneficial to your garden in the process.

Detecting Spider Mite Infestations

If you are going to be able to fight and control spider mites in your garden, the first step is knowing when you have a problem on your hands. To stop a spider mite attack in its tracks, you will have to be able to detect the infestation and identify that you’re dealing with spider mites as soon as the problem begins. Signs that you have a spider mite infestation include the following.

When spider mites have been using your garden as a buffet, you may see yellow, tan, or white spots on the leaves of your plant. These spots are the result of the feeding of spider mites.
If you look closely at affected plants, you’ll see tiny red or white spots on the plant that move. (These are the mites themselves.) If you take a look at them under a magnifying glass, spider mites will appear to be a reddish-brown shade or can be yellow and green.
Webbing will appear on the underside of your plants’ leaves during a spider mite infestation. This webbing will be white with a cottony texture.

Once you have identified the infestation and determined that spider mites are the culprit, it’s time to isolate the infected plants immediately and begin taking the necessary steps to kill the attacking spider mites.

The Life Cycle of the Spider Mite

The spider mite overwinters as an obnoxious egg attached to the affected plant’s foliage or bark. When the weather starts to warm up in early spring, the spider mites’ six-legged larvae start to hatch and feed. Once they’re full, it’s on to finding shelter and changing (or molting) three different times—and gaining two legs—before emerging as a fully grown adult mite. The process of changing from a spider mite larvae to an adult can take as few as five days. In hot, dry conditions, female mites can produce over 300 eggs per day after they’ve mated.

The Spread of Spider Mites

Spider mites glide in the wind from plant to plant. They use their webbing (that cottony stuff on the underside of leaves) to ride the breeze. This method of travel lets the spider mites spread their territory to reach quite far if they’re not caught and contained quickly and carefully.

Because spider mites are barely big enough to see with the naked eye, they can invade a garden without you noticing if you are not vigilant. Whenever you’re working with your plants. Be sure to check the undersides of leaves for small white or reddish dots so you’ll see if a plant is infected. Take note of any damage to the leaves of your plants, and if you find spider mites, take the necessary steps immediately to contain them, then toss out any and all infected plants.

Spider Mite Damage

Aside from spots on the leaves of infected plants and some webbing on the underside of the leaves, large infestations of these tiny little mites can cause serious damage to your crops. You’ll know spider mites have been at your garden when leaves start to look damaged, showing tiny spots or stripes. After a little time, your plants’ foliage may begin to change color, shrink up, or may even fall off completely. Spider mites can impact the yields of vegetable crops, cause direct damage to the fruit of bean and pea plants, and can even kill your plants if the infestation is severe and is allowed to progress untreated.

How to Fight Spider Mites

Taking on a spider mite infestation is not a lot of fun. However, if you catch it early enough, and you have the patience, willpower, and know-how, you can control spider mite infestations using either natural or chemical solutions.

Spider Mite Control: Natural Methods

One natural way to treat your garden for spider mites is to isolate the infected plants and blast them with water to literally knock the mites off the plant and drown them. Containing a mite infestation with this method will take several rounds of treatment, as there are always a few mites that seem to evade the blast or dry off and come back to the host plant. Another natural method of treating spider mite infestations is to go on the offensive and purchase parasitic mites or ladybugs from a nursery or garden center, then release your army of ally insects near the infected plant or plants.

Spider Mite Control Methods

Some of these methods kill all insects, not just spider mites. There are a few treatments, however, that are successful in treating spider mites. Neem oil (an organic insecticide made from the Indian Neem tree), insecticidal oil, and miticide are all effective at treating spider mites.

To use neem oil or a different insecticidal oil to treat against spider mites, first remove all the webbing you possibly can from the undersides of leaves. Make sure to do a thorough job when you’re inspecting your plants for webbing and removing what you find, because the delicate threads can protect the tiny mites from the oil you’re about to use against them.

See the label of your insecticidal or horticultural oil for application instructions. To use neem oil against spider mites, mix up a combination of one teaspoon neem oil per liter of water, or whatever the label says on your bottle. Use warm water to create this mixture, then allow your treatment to come to room temperature. Make sure the water is truly warm and not hot, however, as temperatures that are too high can cause neem oil to be less effective. To get the neem oil to truly mix in the water, you’ll need to add a surfactant. The most common surfactant you’ll have on hand is dishwashing soap. Use just four or five drops per liter of your mixture.

Once you have your treatment mixed, use a one-handed pressure sprayer or atomizer set to the finest mist possible to spray your affected plants. Make sure the liquid reaches the tops and bottoms of the leaves for maximum coverage. Whenever you can, turn plants around a full 360 degrees in the mist so they get treated all over.

Use this treatment once every 10 days to keep your plants protected against spider mites. However, cease using neem oil when three weeks remain until harvest. This stuff is so strong that it can actually impact the flavor of your crops if you don’t lay off the treatments for three weeks before you’ll pick your harvest.

Videos About Preventing Spider Mites in the Garden

This “simple and safe” spider mite solution video has received rave reviews from commenters:

Check out this tutorial from YouTube gardener MissOrchidGirl to get her homemade recipe for a nontoxic spider mite insecticide:

Dive into spider mite defense completely with MissOrchidGirl’s complete 23-minute how-to guide for getting rid of spider mites, including the recipe in the video above:

The best way to fight spider mites is to never have an infestation in the first place. This how-to video teaches you methods for preventing spider mites becoming a problem in your garden: