What is a red spider mite?
The red spider mite (tetranychus urticae) is a type of mite that usually infects cannabis crops while feeding on the leaves. This pest breeds quickly and they eventually build cobwebs around the flowers, so you’ll want to avoid them at all costs. Its ability to develop resistance to pest controls worries any grower. They generally live on the underside of plant leaves, where they can form silk cloth.
They are less than 1 millimeter in size and can be red or black. They prefer warm and dry conditions and lay transparent eggs that can hatch in just 3 days. The offspring are sexually active 5 days after birth, and can live up to 2-4 weeks, laying up to 20 eggs per day.
How to fight the red spider mite?
Observation is key to spotting the red spider. Some people can see them moving down the back of the leaves, while others need help of a magnifying glass to spot them. Either way, be sure to regularly inspect the plants, and if you’re looking at cobwebs, you’re certainly dealing with an infestation of this insect. The appearance of a few bugs does not mean that there is necessarily a plague. If some red spiders mites are found under the leaves, they can be plucked and thrown into a bag away from the crop, but keep watching and check that they do not multiply.
Prevention is key and high humidity will slow down the reproduction rate of this pest, so spray plant foliage frequently with water. There are also home remedies; some growers water the plants with a mixture of water and alcohol (9: 1) as it kills the mites without hurting the plants.
If your plant has already started the flowering stage, it is best to use natural products so as not to hurt the plant. The use of potassium soap is a good solution to control this pest. This product is a combination of vegetable fats mixed with an alkali (product with a very high pH) and two or three applications should be applied at intervals of five to ten days, until the hardest day.
On the other hand, biological control is one of the best methods to fight the red spider mite. You’ll need natural predators that must be introduced into the crop. They are totally harmless to the plants and feed on the red spider mite. The best known are: Phytoseiulus persimilis, Noeseiulus Californicus and Amblyseius swirski.
Specific chemical insecticides for this type of pest also work, but they should be used with precaution and only if the plant is already infested, as they are not preventive. These products are known commercially under the name of acaricides or miticides. Ideally, apply them before the flowering stage, at which point it will be much more difficult to combat the pest.
Lastly, you will want to clean your grow room, grow tent, or greenhouse if you had this type of pest. There are many ways to clean and disinfect using products like hydrogen peroxide or alcohols. Be thorough, be clean, and be patient.