Spider mites – every cannabis grower’s worst nightmare.
Spider mites are members of the Acari family. There are over 1200 documented species in the mite family. Spider mites are less than 1 mm in size (between 0.4mm and 0.5mm), and they also vary in color. They have four pairs of legs, no antennae and an oval-shaped body. They lay small, round eggs which are transparent at first.
Many species of spider mites spin silk webbing to help protect the colony from predators. This is where they get the “spider” part of their common name. The best known member of the group is Tetranychus urticae, commonly known as ‘red mites’ or ‘two-spotted mites’. The idea of encountering these mites in one’s grow area is enough to make any grower shudder.
Spider mites generally live on the undersides of leaves of plants, where they may spin protective silk webs. They can cause damage by puncturing the plant cells, which is how they feed. Spider mites are known to feed on several hundred species of plants, but they particularly enjoy feeding on the sap and plant tissue of cannabis sativa. They know what’s good.
Hot and dry conditions are often associated with an infestation of spider mites. Under ideal conditions (approximately 27 °C), the two-spotted spider mite can hatch in as little as three days, and become sexually mature in as little as five days. One female can lay up to 20 eggs per day, and can live for two to four weeks. This accelerated life cycle allows spider mite populations to adapt quickly to pesticide resistance, so chemical control methods may become ineffective when the same pesticide is used over an extended period of time. This doesn’t matter to us because we don’t do chemicals. Ever.
SIGNS OF INFESTATION
Spider mites are so tiny in size that they often go unnoticed by the naked eye. (Investing in a jeweller’s loop is a great idea for any grower, and not just for checking out your ambering trichomes. Use it to inspect your plants thoroughly and regularly!) Upon closer inspection, spider mites appear like small amber or pale green dots. They are mostly found on the underside of leaves.
If you have no jeweller’s loop or magnifying glass, one way of checking for spider mites is to hold a piece of blank white paper under the leaves and carefully shake the plant. If you find peppery looking spots on your paper, it’s likely that you have a mite infestation on your hands.
Some initial signs of a spider mite infestation include tiny white spots or dappling of leaves. These little spots of discolouration are visible from the top of the leaf, too. Often, thin and silky webs can be found surrounding the underside of plant leaves and branches.
More serious infestations can cause leaves to turn yellow, become limp and die off altogether. A large spider mite infestation can have a remarkably detrimental effect on a cannabis plant. By attacking and destroying the plant’s leaves, they may stunt its ability to develop and grow; inevitably resulting in much lower yields.
Spider mites may also infest the surrounding areas of cannabis flowers, which can inhibit their ability to develop properly. In a nutshell; your buds will be small and lacking in both potency and flavour, and there won’t be a whole lot of them either.
Finally, a large enough colony can kill entire plants, although that is a very rare occurrence. The severity of such an infestation involves a level of negligence which ought to be punishable by death. Check on your ladies. Check on them every single day.
Generally speaking, spider mites thrive in a hot and dry environment; while cooler, breezy and more humid conditions slow their reproductive rate significantly.
Owing to their incredibly tiny size, spider mites can quite literally float into your grow area on a slight breeze (or on a cloud of smoke, should they choose to arrive in style). They’re well-known for their windsurfing skills. If you’ve ever felt that you’re “too small to make a difference”, you haven’t encountered spider mites.
They are also often introduced to indoor grows from other house plants in the area, or from new plants and clones that have been introduced into the grow area without quarantining them first. Yes.. your buddies may often tempt you with cutting or clones from awesome genetics, but be doubly sure to keep them in quarantine for at least two weeks Mites have also been known to travel on shoes and clothing, as well as on the coats of your pets. Mites (including pregnant ones) can also lay dormant for extended periods of time, until the conditions are favorable enough for them to thrive again.
We’re quite sure that you are now beginning to understand why we started by saying that spider mites are quite possibly every grower’s worst nightmare. They are near impossible to prevent, extremely difficult to detect, and a huge ball-ache to eliminate.
The following are organic methods which can (and should) be put in place as a preventative measure. Prevention is ALWAYS better than cure, especially when growing with living soil and organic techniques.
1. Companion plants
A great environmentally friendly way of helping prevent a spider mite outbreak is by making use of companion plants.
Companion planting is a process whereby the growing environment is improved by planting beneficial plants close to one another. Companion plants protect other plants against pests by emitting a strong odour that is said by many to help deter spider mites from reaching your cannabis plants.
Some of the best companion plants for keeping spider mites away from your cannabis plants include Chinese parsley, cilantro, coriander, dill, garlic, pyrethrum, fennel, cloves, chives and onions.
2. Neem Oil
The application of neem oil every ten days acts as a preventative measure for pests and pathogens. Prevention is always the best policy. It is, however, very important to prevent neem oil from coming into contact with your cannabis flowers. For more information on neem Oil, please see the section on neem.
3. Essential Oils
Eucalyptus, cinnamon, lemon, peppermint and rosemary essential oils are all useful in preventing spider mites when diluted heavily with water and used liberally as a foliar spray. Essential oils attack the nervous system of the spider mite, and they work well as a preventative measure. It is, however, very important to prevent essential oils from coming into contact with your cannabis flowers to avoid changing their taste and smell. No one wants to smoke peppermint flavoured Cheese, or eucalyptus flavoured Sour Diesel.
Once you’ve identified spider mites in your grow area, it’s imperative that you act immediately. It is essential to ‘attack’ all stages of the spider mite’s life cycle in order to combat the infestation most effectively. This is going to be hard work, but it’s not impossible.
The first option is to set your entire grow room on fire, and move to a new house. If this is not a plausible option for you then keep reading for a list of measures which should collectively assist in getting rid of your spider mite infestation.
Pruning and cutting
The logical first step would be to physically remove as many of the mites as possible by pruning and cutting off any infected areas, including (and well past) the areas where any webs are found. Dispose of these off-cuts by sealing them an airtight bag and throwing them in the dustbin!
With severe spider mite infestations, it is worth considering destroying the affected individual plants entirely. This prospect is enough to bring a grown man to his knees, but sometimes “a man’s gotta do what a man’s gotta do”.