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Spider Mites Tetranychus urticae

Spider Mites

There are over 1,200 species of spider mite in the world. The two-spotted spider mite, or Tetranychus urticae Koch, may be the most common pest in Cannabis production. [Read More]

There are over 1,200 species of spider mite in the world. The two-spotted spider mite, or Tetranychus urticae Koch, may be the most common pest in Cannabis production.

two spotted spider mite

Two-spotted spider mites are easily identified by the two ‘spots’ on their back. These spots are actually food waste that is visible through the body of the mites. The mites use their delicate mouthparts to feed upon individual cells on the undersides of leaves, causing the classic stippling damage that indicates their presence.

 The webbing commonly associated with spider mite infestations has many uses besides protection. The mites will sometimes use the silk as a ‘sail’ catching the wind to travel.

What to look for:
  • Leaf stippling and webbing
  • Spider mites thrive in high heat and low humidity 


Life Cycle of Spider Mites



Two-spotted spider mites have 5 life stages. They go through a ‘resting’ phase after each molting.

Egg- Spider mite eggs are spherical in shape, creamy in color, and are often laid in groups.

Larvae- The larvae have only 6 legs, and are a light yellow color.

Nymphs- There are two nymphal stages: Proto- and deuto-. The nymphs also have 8 legs and are yellowish green in color.

Adult- Females are larger than males. They have 8 legs, though both sexes have the two ‘spots’ visible through their body wall.


  •  Twos-potted spider mites can develop between 54 and 104˚F.
  •  They thrive in hot, dry conditions.
  •  At the optimum temperatures, ranging between 86˚ to 90˚F, they can go from egg to adult in 6 days.
  •  The egg laying habits of females depends on both temperature and food availability, though on average a female spider mite will lay 10 eggs per day at 77˚F.
  •  Diapause in two-spotted spider mites is initiated by a combination of short day length (>13hrs), lack of food, and/or low temperatures. Adult mites undergoing diapause may appear orange or crimson in color. A fixed chilling period is necessary to terminate diapause.

I see spider mites, now what?

There are many forms of bio-controls for Two-spoted spider mites, but the most effective predators that we have seen in the presence of spider mite infestations are Persimilis and Californius. Since persimilis STRICTLY feeds on two-spotted spider mites, it is a great hot-spot, or curative, treatment.  In some cases, 2-3 applications, approximately 5-7 days apart, will be necessary to get mites under control.

I don't see any, but I'd like to act preventatively....

While Persimilis is the best option for established infestations, there are a few other species that will feed on two-spotted spider mites and are packaged in sachets for preventative control. Sachets usually allow predators to continuously reproduce and emerge from the sachets onto the canopy for 3-5 weeks. Californicus and Andersoni are good options, though factors such as the presence, or potential presence, of other pests in the garden and environmental conditions, like temperature and humidity, will dictate the predator of choice. Please read the brief descriptions below and see what is going to be the best option for your operation. 

 Additional Notes

* Thrips can feed on spider mite eggs, but we don’t recommend relying on them as a method of control!

FAQs About Spider Mites

How do I know if I have Spidermites?

The most common Spidermite in agricultural/horticultural facilities is the Two-Spotted Spidermite, Tetranychus urticae. Populations of this pest can best be categorized in three levels: Low, Medium, and High, or 1, 2, and 3 respectively. Level 1 Spidermite indicates one or two individual adult or nymph mites on a leaf with minimal damage observed. Level 2 Spidermite indicates larger populations on a leaf made up of all life stages (egg, larvae, nymph, adult) with more obvious damage symptoms. Level 3 indicates a full breeding ground complete with webbing, significant crop damage, and all stages of the pest's lifecycle present.

How do you get rid of Spidermites?

Spidermites are attacked by the natural enemy Phytoseiulus persimilis which feeds exclusively on Spidermite. Persimilis feeds voraciously on the pest and can easily traverse their webbing. When introduced preventatively or in great enough numbers, the Persimilis will eventually feed on every Spidermite on a plant, crashing both the pest's population as well as its own.

What causes Spidermites?

Spidermites are a cosmopolitan pest of plants which occur in every temperate region in the world. They can easily be brought into a facility on propagated plant material, on employee's clothing, or even through the air on small strands of webbing they use as a sail to distribute on wind currents. Spidermites prefer hot, dry conditions which cause plant stress.

How do you control two spotted spider mites?

While there are a wide variety of approaches for effective TSSM control, the method of choice will largely depend on the variables that are unique to your grow. In general, for a curative approach to controlling an established population of spider mites during the vegetative or early-flower period, you might want to start with our Spidex products. If you've dealt with the TSSM in the past and are not wanting to deal with them again, you might want to utilize our Spical Ulti-Mite sachets. Again, the approach you choose will depend on your growing situation, so if you'd like further assistance choosing the right product for you, please contact our customer service team!

What does a two spotted spider mite look like?

An adult Two-Spotted Spider Mite is about 1/50 of an inch long, or in other words, nearly impossible to see any detail with the nake eye. Under magnification, however, you will see a beige body with what look like dark 'spots' on either side of its dorsal section. Nymphs and eggs both look slightly different, but as with most cannabis pests magnification is crucial in order to be 100% sure of what you are dealing with.

What are signs of spider mites?

Subsequent to feeding on the plant tissue, TSSM leave behind what people often describe as 'speckling' or 'stippling' on the top of the leaf surface. The speckling will be prolific and not be contained to certain parts of the leaf, but will look like a collection of very tiny white spots over the entire leaf surface. In addition, once populations reach concentrated enough levels, the spider mites will begin to fortify their territory by spinning fine webbing, which also allows them to traverse the canopy with greater ease. If you see this type of webbing, it is for sure there are spider mites in the area. No other common cannabis pest spins web.

What's the lifespan of a spider mite?

Given optimal conditions (approximately ~80 °F & low RH), TSSM's can hatch from their egg in 3-5 days. Once they reach adulthood, which can occur in as little as 5 days, each female has the capacity to lay up to 20 eggs per day and can live for 2 to 4 weeks, laying hundreds of eggs during that time.

Should I throw away plants with spider mites?

While the decision to purge infected plants rests with the grower alone, the talented team at Natural Enemies can certainly provide guidance and explain all of the available options, allowing you to make an informed decision regarding your grow.

Questions About Spider Mites?

Our team of experts is at your disposal to help you make the best decisions according to the particular needs of your crop. Do not hesitate to call us during normal business hours at (503) 342-6698 or write us through our chat to provide you with personalized service. We will be more than happy to help you!