How to Get Rid of Spider Mites

By August 19, 2019 August 24th, 2019 Gardening Inspiration and Advice
royal city nursery guelph spider mites infestation

What a wild ride the weather in Guelph has been this year! Just weeks ago, we were all feeling gloomy because it was too wet, and now we’re all running our water bills trying to compensate for a sudden wave of dry heat. While most of us certainly don’t mind the change (after all, it’s perfect weather for hitting the lake!), you may have noticed someone else taking advantage of the current climate at your expense. That someone is the spider mite, a tiny terror who is coming for your garden plants— and bringing her millions of family members with her.

If you think your property might have become the venue for a spider mite party, stay calm. I have plenty of tips for getting rid of these ghastly pests from the many places in your yard where you might find them.

How to Tell Your Plant Has Spider Mites

Spider mites are just as nasty as they sound, combining the most hated traits of two unpopular creatures into one especially unpopular garden pest. Spider mites are tiny arachnids, normally red or light brown, that breed quickly into large colonies and feed by sucking the juice out of your favourite plants (not unlike the equally-disliked aphid). However, since they are related to spiders, they also produce messy webbing— the cherry on top of an already unnerving infestation.

A plant that has spider mites will initially show slight discolouration on the leaves, appearing finely speckled with pale green or yellow. This kind of damage is also known as “stippling”. If the spider mites aren’t caught right away, they’ll make themselves known soon enough with masses of fine webs all over the surface of the plant. At the first sign of discolouration, check the underside of the leaves and look closely for mites, which will appear to be tiny brownish or reddish moving specks. The earlier you catch them, the easier it will be to boot them out!

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How to Get Rid of Spider Mites on Shrubs and Trees

On large plants like shrubs and trees, the mite problem has to get very severe to compromise the whole plant. However, because the mites tend to target some shrubs (like junipers), reproduce quickly, then spread to other plants, it’s very important to nip the problem in the bud if you see any signs of them. If you do notice spider mite damage on an established shrub or tree, the first thing to try is a good spray from the hose.

Before spraying, clip off any areas where the damage seems to be the most severe and immediately dispose of the clippings in a garbage bag. Avoid doing this on windy days—spider mites are incredible escape artists and may use the opportunity to ride the wind onto your neighbouring plants.

Then, use your garden hose on a setting that has good pressure— enough to give the leaves a good wash but not strong enough to knock them off the branch. Spray the plant thoroughly, focusing on the undersides where the mites like to hide. Repeat this process every day for about five days to make sure you’re targeting new mites as they hatch. 

After the fifth day, give your tree or shrub a break and keep an eye out for new damage or webs over the following week. If the infestation persists, try using the all-natural power of chrysanthemums with CIL’s BioMist.  Spraying will be more effective in the early morning or late evening when temperatures are a little cooler. Available in a ready to use or concentrate you mix with water according to the recommendations on the packaging, apply the solution to the affected plant. Repeat application seven days later. 

royal city nursery guelph spider mites webbing

How to Get Rid of Spider Mites in Soil

When the soil is dry, like it has been in most Guelph gardens lately, spider mites will infest the soil in your garden as well as the plants. It can be tempting to use a pesticide on the soil to get rid of spider mites fast, but that would be a major rookie mistake.

The soil is home to millions of life forms, many of which are beneficial and even predatory to the mites. When you coat the ground in an insecticide, you kill the good with the bad. This may actually achieve the opposite of what you intended, as suddenly the mites have fewer predators and their populations can balloon even further out of control.

Soil moisture is the enemy of the spider mite. Keep the soil near infested plants well watered with cold water to keep it inhospitable for mites. Your plants, on the other hand, will be very appreciative.

How to Get Rid of Spider Mites on Edible Plants

If you’re wondering how to get rid of spider mites on tomato plants versus how to get rid of spider mites on cucumber plants, the good news is that they both have the same solution. When it comes to vegetables, I’m of the opinion that the fewest possible chemicals are the best way to go. Luckily, there’s a very effective chemical-free solution for mite infestations in your vegetable garden: insecticidal soap spray. Come visit us at our garden centre in Guelph and we’ll set you up with a good soap base for tackling that mite problem.

How to Get Rid of Spider Mites Indoors

It’s bad enough to share your garden with spider mites—so what if they start moving into your home? Houseplants make ideal hiding spots for spider mites, especially if the air in your home is quite dry and warm. 

Since using water alone on a houseplant can run the risk of overwatering the plant, applying a solution of water and insecticidal soap is your best bet, just like you did with your edible plants. Spray it on the plant (again, focusing on the leaf undersides and avoiding the flowers) as well as the soil surface. Apply the solution every two days for a week, then monitor the plant during the following week to make sure the pests are gone.

Make sure to water houseplants regularly after treatment to prevent another infestation from popping up, but make sure the soil has dried out in between watering so you don’t end up drowning the plant.

Last Resorts

If you haven’t caught the infestation early enough, you may find yourself looking for a last-ditch solution. 

Organic pesticides like BioMist, which is a pyrethrum-based insecticide, can be used to manage a severe spider mite infestation. Speak to a specialist at our location in Guelph for help choosing an appropriate product, and follow the package instructions very carefully.

If a plant is truly overtaken by spider mites, sometimes the best thing to do (rather than douse it with chemicals) is to cut your losses and dispose of the plant. Put a plastic bag over the plant before removing it to keep mites from jumping ship, and treat the soil around the plant and neighbouring plants to prevent them from starting up a new lifecycle.

While spider mites are never welcome in the garden, they’re not especially tough bugs (like those dang Japanese beetles!) and they can be controlled fairly easily if caught in time. Take a page out of a farmer’s book and scout for spider mites — and other nasties — daily. That way, you’ll always have a leg up on these eight-legged pests.