Spider mites are tiny arachnids that can damage indoor and outdoor plants. They can be difficult to see, but heavy infestations cause stippling and discoloration of foliage.
Keep houseplants watered and weed free to reduce stress that can make them more vulnerable to pests. Use a water spray to wash plant leaves regularly, particularly the undersides, to remove dust that is a favorite hiding place for mites.
Identifying a Spider Mite Infestation
Several species of spider mites can infest plants and damage them. They can be hard to spot because they are so small. The best way to tell if a plant is infested with these tiny arachnids is by looking for webbing on the leaf surface. Infestations can cause severe damage to plants, especially those that are already stressed by other conditions. Infestations can even kill them if left untreated.
Infestations are more common during hot and dry summer weather. These conditions also help to increase the spread of the mites. The mites overwinter as eggs on vegetation and hatch from those eggs when temperatures are high. They can reach populations of large numbers very quickly under these conditions.
When the weather is warm and dry, spruce spider mites can become a problem for evergreens such as spruce, pine, hemlock, arborvitae and false cypress. This mite feeds on the underside of leaves, using piercing mouthparts to suck the sap. Heavy infestations can result in stippling, distortion, yellowing and premature needle drop.
Two-spotted spider mites overwinter as eggs on the ground or in debris and then hatch into larvae when temperatures are warm. These grow into nymphs and finally adult spider mites in the same manner as other arachnids. Adult mites are light green to yellowish in color and are about 1/50th of an inch long. Juvenile mites are smaller and have six legs, while the egg stage is clear and resembles a sphere.
The first symptom of a spider mite infestation is usually pale, yellowed leaves. Leaves may look stippled and distorted, with the margins of leaves often being more affected than the midsection. As the infestation becomes heavier, the leaves will turn brown or yellow and may eventually die off entirely.
The easiest way to prevent a spider mite outbreak is to routinely spray down all of the foliage on your plants, including the undersides and tops of the leaves. This should be done on a regular basis, perhaps every month or two. This will also help to keep dust off the leaves so that aphids and thrips have less of a chance of infesting them.
Treatment
If you discover a spider mite infestation on any plant, it’s important to treat it right away to prevent the pest from spreading to other plants. Start by isolating the infested plant from other indoor houseplants, keeping it at least several feet away until the pests are eradicated. Then, carefully inspect the plant and remove any sections with visible webbing, disposing of them properly & thoroughly.
If stippled leaves are present, you will need to use a 10 – 20 power hand lens or microscope to see the mites themselves, which are small, oval in shape and translucent. You may also notice spherical, pale-colored eggs or strands of webbing on infested leaves or between branches.
Moderate to heavy infestations of two-spotted mites can be controlled with insecticidal soap or horticultural oils, both of which work by smothering the mites. Be sure to read all product labels thoroughly, as some may injure or discolor certain plants.
Keep in mind that the best way to limit mite outbreaks is by promoting healthy, stress-free growth. This means feeding plants with a well-balanced fertilizer derived from fish, seaweed or plant extracts, and maintaining proper lighting conditions. In addition, adequate irrigation can help reduce drought stress that encourages mite outbreaks.
You can also promote a healthier environment for your plants by pruning them frequently and removing any dead or diseased leaves. This will keep the foliage clean and help deter spider mites by reducing their hiding places. In addition, regular hosing down with a forceful spray of water (at room temperature) can physically remove some mites and interrupt their web-laying habits. It’s a good idea to hose down the entire plant, including the underside of the leaves, and to repeat this procedure once or twice per week until mite populations have been reduced.
Prevention
The first step in controlling a spider mite infestation is to isolate the plant. This will help prevent the spread of the pest to other plants. Once the affected plant is isolated, it should be inspected and treated. If a severe infestation has already developed, it may be necessary to dispose of the plant. In most cases, if the infestation is caught early and treatment is started right away, it is possible to restore a plant to good health.
The most visible sign of a spider mite infestation is the presence of fine webbing, which looks like tiny spider webs. These webbings are found on the undersides of leaves and in the crevices between leaves. The fecal matter and cast-off exoskeletons of mites also build up on leaves, giving them a gritty texture. In the case of a severe infestation, the top surface of the leaves are peppered with tiny spots of discoloration and become yellowed and brittle.
It is important to monitor a plant for the presence of these pests, especially during warm, sunny weather when mites are most active. Damaged leaves can be mistaken for heat stress or drought, so it is important to determine if the symptoms are caused by mites or another condition before applying a treatment.
There are several ways to treat a spider mite problem, including horticultural oil, natural predators, and chemical insecticides. However, we highly recommend avoiding the use of synthetic pesticides, as these are harmful to other beneficial insects and can contribute to the development of resistant organisms. We also advise against using pyrethrins, which are derived from chrysanthemums and can be toxic to many plants.
Predatory mites (such as Phytoseiulus or Amblyseius) can be purchased and released on infested plants. They are effective in controlling spider mites and other pests, but must be applied regularly to be effective. Another effective way to control a spider mite problem is to use a water and rapeseed oil solution. Apply the emulsion to the affected plant, focusing on the undersides of the leaves and in any nooks and crannies where mites might be hiding. It is recommended that this be done in the evening to avoid damaging the plant’s cuticle.
Getting Rid of Spider Mites
If you spot webbing on your plant or notice general leaf damage, you have a spider mite infestation. You can confirm the presence of these microscopic pests by placing a leaf under a white sheet of paper and looking for mites moving around. They’re hard to see without a magnifying glass, but they’re easy to identify by their fine silky webbing and general leaf damage. Infestations of this type usually become more noticeable in warm weather because the tiny mites thrive in a dusty, hot environment.
The good news is that there are several ways to get rid of spider mites on plants. You can use natural solutions, more intense miticides or a combination of both. First, try to increase the humidity of your houseplant. This will discourage the pests, who prefer warm and dry conditions. You can also wipe down your plants with a damp cloth or a makeup brush. This will remove the mites as well as debris that can encourage their return.
A spray of horticultural or insecticidal soap can also be effective. Follow the product instructions and apply it to the leaves of your infested plants, being sure to cover all the surfaces, including the undersides. Be careful not to over-spray, as this can injure your plants. Insecticidal soaps and horticultural oils are most effective when applied at the first sign of a mite problem, since new mites can hatch within a week.
Neem oil is another common and highly effective natural pesticide. It’s available in a variety of forms, including a ready-to-use spray and a powder that you mix with water and pour onto the soil. You can also find neem oil in a variety of home-use products, such as spray bottles and cleaning products.
More extreme measures include the use of contact and systemic pesticides, which can be mixed with water and sprayed on the plant or sprinkled as a granular product on the soil. Contact pesticides kill only those insects that come into direct contact with the chemical; systemic pesticides enter the plant and kill any insects that feed on it.
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