How to Get Rid of Spider Mites on Your Houseplants

Whats Bugging You?

Spider mites are unfortunately a common houseplant pest that can appear anytime of the year but especially in winter when our houses our warm, dry and lack humidity.

Technically they are not insects but incredibly tiny arachnids with eight legs (cousins to spiders) that love to pierce the cells of leaves and feed on the chlorophyll. To add insult to injury, they multiply very quickly and will take over a plant in a fairly short amount of time. Adult females lay hundreds of eggs over the course of their lifetime which (indoors) is three to four weeks. The eggs hatch in 3-4 days.

How to identify if you have spider mites.

The most common spider mite that attacks houseplants is the two-spotted spider mite. They have an oval-shaped reddish or light green body with a dark spot on either side of the abdomen.  Keep a magnifying glass handy, as it is very hard to see them.  They usually first appear on the underside of leaves looking like very tiny black specks. There may or may not be a bit of webbing that glimmers when held up to a light or a sunny window.

Hold a white sheet of paper under your plant and gently shake the plant or tap the leaves. Spider mites will appear on the paper as tiny black grains of sand and some will be moving.

Spider mites will produce a very fine webbing over the leaves and along the stems in a heavy infestation. At this stage the webbing is visible and the mites are hard to get rid of.

As they feed, they will produce a flecking effect of tiny white or yellow dots on the top and undersides of the leaves. Feeding destroys plant cells and causes the leaves to turn yellow and fall off the plant. 

To stay a step ahead of spider mites, be proactive, vigilant and routinely check your plants. If you have moved plants indoors for the winter, isolate them for a couple of weeks and routinely check for spider mite (and other pests) before putting them with your houseplants.

If your home is dry, buy a cool mist humidifier. If your home humidity is below 40% in the winter, run your humidifier in the morning for a few hours. Make sure the size of your humidifier is adequate for the square footage of the main area where you display your plants. Too much humidity may encourage mold.

Keep your plants healthy and happy. Spider mites like to attack weak plants that are not doing well. Check for mites when you water.

Give your plants a warm shower routinely (preferably when you water). Wipe down the front and back of large leaved plants. You can also wrap the pot in a large plastic bag, secure around the base of the plant to avoid getting the soil too wet.

Indoor plants with thick, tough leaves such as jades, succulents, cacti and ZZ plants are less prone to spider mite attack but do include them in your regular insect inspections.

Treatment

When treating plants indoors, I would rely on natural ‘miticides’ or predatory insects. There are chemical miticides on the market but I would not use them in the home during the winter. Because spider mites are arachnids, insecticides are not effective.

The following treatments are most effective during the early stages of an outbreak.

Treatment of spider mite infested plants involves a consistent time commitment on your part. If a plant is too heavily infested, I would consider throwing out the plant. It is totally up to you. Do not compost.

First isolate the affected plant. Check the other plants that are close to it as well. Keep the soil slightly moist but not soggy. Spider mites usually do not live in the soil but may be on the surface.

If very few leaves are affected, remove these leaves (disinfect your pruner) and treat the plant (see below).

Many people like to release beneficial insects such as predatory thrips, mites, or ladybugs; but there must be spider mites present before the good bugs can be of any benefit.

Beneficial insects/mites also have to be released routinely to be effective. If you are using beneficial bugs, you cannot use natural miticides, as they may also kill the beneficials.

When using the following natural treatments I would first test them out on a leaf or two before doing a blanket spray. Always wear gloves and label all spray bottles.

Soap Solution 

A soap solution will stick to the mite and suffocate it. Mix 1 litre of water with 5 ml. of Dawn dish detergent in a fine mist spray bottle. Shake well and spray the plant, making sure you spray the underside of the leaves as well. Let the plant sit for about 15 minutes and rinse it off thoroughly with warm water. Repeat every three to four days for a total of 4-5 applications.

Rubbing Alcohol

Rubbing alcohol dehydrates the mites. Mix 250 ml of alcohol with 1 litre of water. Add a couple of drops of blue Dawn dish soap, shake and spray down the plant. Leave this on the plant for a couple of hours, then rinse the plant thoroughly. Repeat at one week intervals if you still see some mites. Do test this solution on a couple of lower leaves before spraying the whole plant. Some plants are sensitive to rubbing alcohol.

Neem Oil

Neem oil is a natural pesticide and is derived from the seeds and fruit of the Neem Tree. This oil contains azadirachtin which is an active compound that interferes with the growth and reproduction of many soft bodied insects and mites. It will also quickly kill by suffocation. You do not have to rinse off neem oil –it will break down within a few days.

You may need to make more than one application. As a miticide, use Neem once a week.

Neem oil is non-toxic to humans, pets and other animals but very toxic to fish and other aquatic creatures. Be careful not to get it on your clothes or furniture.

Do not use Neem on recently transplanted houseplants or plants with hairy leaves. Always follow the directions on the bottle.

Wear gloves as Neem has been known to be slightly irritating to the eyes and skin. A Neem oil/water mix can also be used when wiping down your plants.

Kelpy Neem Oil is an organic neem oil. It is produced by a Canadian company from British Columbia and is sold by Floral Acres.

Rosemary Oil

Rosemary oil is deadly for spider mites. Add 10 ml rosemary oil to 1 litre of water. Mix well, shake and spray. I would shake this mixture between sprays as well. Apply two times a week for 3 applications. Rosemary oil breaks down naturally on its own in a few days. Research shows that rosemary oil interrupts the egg laying stage of spider mites - reducing mite populations after each application.

Hydrogen Peroxide

Hydrogen Peroxide can be used as an insect spray and is non-toxic. Mix 250 ml -3% hydrogen peroxide with 250 ml distilled water in a fine mist spray bottle. Hydrogen peroxide will not kill the mite eggs so repeat weekly until you are confident the mites are gone.