If you’ve come across spider mites on your buds or plants, or you’re dealing with an infestation in your garden, you may be wondering whether these industrious little critters will spread to you!
Spider mites are a massive family of tiny sap-sucking arachnids which are alluded to fed on multiple species of plants.
They are indeed little spiders, and exist in no relation to us humans, as the mouthparts and digestive system are designed for sucking sap and cannot bite us.
They have specifically adapted to living on and feeding from plants, which may make them a pest.
In This Article: We will take a closer look at the spider mite, and get you set up with some tactics to really get rid of them from your plants!
What Are Spider Mites?
If you’re an attentive vegetable or greenhouse gardener, you may have battled varieties of sap-sucking attackers which are capable of infesting and overwhelming otherwise healthy plants while given the opportunity.
Spider mites are another sap-sucker and along with mealybugs and scale insects, they reproduce on infected plants while feeding on its sap.
Of the three types of sap-suckers described above, the spider mite is the only arachnid, which means it not an insect; in fact, there are over a thousand species of spider mite and they are one the most diverse family of arachnids in existence.
They’re all super tiny, under 1 millimeter in size and actively spin silk webs to shelter themselves and their eggs on the undersides of the leaves of plants.
Spider Mites Are 100% Adapted to Living on Plants so They Cannot Survive on Human Skin
Spider Mites Are 100% Adapted to Life on Plants so Cannot Survive on Human Skin
The word “mites” brings to mind itching, bites, and human infestation. But spider mites can only survive on plants.
They prefer to be in warm dry conditions where large populations can develop quickly.
Female spider mites will lay 20 eggs daily throughout their life span of 2-4 weeks feeding off of the plants they inhabit making multiple punctures which are detrimental to plant vigour and health.
As Voracious Feeders and Breeders, Spider Mites Can Quickly Overwhelm an Otherwise Healthy Plant
Tetranychus urticae, the red spider mite is one of the common spider mite species.
It is polyphagous which means that as long as it has a plant to feed off of it is quite happy to feed as basic food.
This variability is what makes it such a feared pest as it can feed on multiple industrially cultivated fruits and vegetable plants like potatoes, tomatoes and maize as well as on ornamentals like roses.
The Bite of a Spider Mite Can Be Deadly… to Plants
The destruction it is capable of to the plant is methodical with each mite feeding on the plant juices individual cell by individual cell to catastrophic effect.
The Spider Mite’s piercing-sucking mouthparts are perfectly suited to penetrate the plant cell wall to access all the nutrient and sugar-rich cytoplasm of the plant cell.
They quite literally pull every bit of liquid out of the plant cell, leaving a white scar on the leaf.
The Process: While each scar from the biting mouthparts of the spider mite is small, the combined impact of thousands of simultaneous spider mites feeding will destroy the photosynthetic potential of the plant, killing it.
Symptoms of a Spider-mite Infestation
The presence and the damage from spider mites is often not detected on plants until the spider mite population has exploded in numbers.
Readily check your susceptible plants for these mites, as well as other plant pests starting in the spring.
Here are some of the plant symptoms and signs that should get you thinking that you might have spider mites:
- Loss of plant vigor: while a non-specific symptom, a loss of growth rate and vigor of your plants should always leave you with an impression that pests must be affecting it.
- Loss of plant height: a weakened plant losing nutrients to parasites will lose height. This should always get you looking more closely at the plant for a possible pest problem.
- Leaf drop: leaves that have been damaged from feeding will dry and drop off affected plants.
- Fine mottling on the upper leaf surface: the feeding of the spider mite will scar individual cells that will show up as tiny pale or white scar mottles.
- Visible mites and eggs: sometimes, visible mites and eggs are noticed on the underside of plant leaves. Mites can range in colour from yellowish to greenish with dark spots, based on which species is present. You’ll need a magnifying glass to see mites properly.
- Silky webbing on the plants: you may also see the silky webbing the spider mites use to hold their eggs, particularly on the undersides of leaves.
Tackling a Spider Mite Infestation
Dealing with a spider mite infestation requires taking fast action if you want to make an effort to control the situation and limit the spread to other plants.
There is an assortment of non-pesticide options available to treat these pests.
Some of the control options will be different from dealing with mealybugs and scale insects but the theory is the same.
Here are the main options.
Unleash Natural Predators of the Spider Mite
Luckily spider mites have a number of predators that will quickly dispatch them and ease the burden on your plants.
They are so effective that these biological controls are more attractive than using pesticides and are now employed as first options when spider mite infestation is suspected:
- Phytoseiulus persimilis is a similarly-sized mite that hunts and consumes the red spider mite. It is extremely active, and will seek spider mite in all growth stages and on the plant, including eggs!
- Amblyseius mites are also predators of the spider mite, and will hunt and kill them year-round.
- The predatory midge Feltiella acarisuga has predatory larvae that consume spider mites, among other sap-sucking plant pests, and are typically most active in the spring while mite infestations are being initiated.
- The rove beetle Atheta coriaria will also feed on spider mites along with its food of gnats and thrips.
Topical Applications and Sprays to Eradicate Spider Mites
Neem oil, pyrethrum, and fatty acids can be sprayed on plants to kill or deter spider mites.
Surfactant sprays can render mites incapable of colonising treated plants.
Taking preventative measures can go a long way in keeping spider mites at bay:
- Increase the humidity: increasing the humidity in a greenhouse or home watering will not eradicate spider mites, but it may help drive them to a plant with lower humidity.
- Remove affected plants: taking strict quarantine measures is critical to not allow spider mites to migratory to other clean plants. Consider quarantining new plants before you bring them into your greenhouse or home.
- Target overwintering: you can target overwintering spider mites by removing plant debris, stakes, and dead leaves in ample time, and before your plants emerge in the spring. Also, consider disinfecting your greenhouse with a glasshouse disinfectant to keep it free of spider mites for the appropriate plant(s).
Rounding Up
It’s apparent that the only issues that spider mites pose for humans is the infestation to their plants!
However, by being careful and intervening early, the spider mite should not be a significant issue for most gardeners.