Mites are probably one of the most invasive and harmful pests that we see in indoor and outdoor marijuana plants.
The red spider mite and the whole mite and microscopic mite family seriously harm plants. They bite and perforate the leaves with their tiny teeth in order to feed themselves, thereby extracting chlorophyll, which is a vital component for the photosynthesis and good growth of any plant.
Additionally, the saliva of the red spider mite contains toxins and substances that cause the plant to become ill and weakens its defenses against other pests such as fungus and bacteria.
You can end up with pests without even realizing it. It’s possible to bring them in from outside of the house, on our clothing, shoes, hair… or, since they are so minuscule, they can piggyback on other insects or on our pets. They may also appear when an imbalance occurs in the ecosystem, or for over or under watering, too much liquid fertilizer, too much or too little sun, low biodiversity, etc.
They reproduce exponentially, making for a rapid invasion, and can kill our plant in as little as a few days. Their eggs mature in 3 days and 5 days after leaving the egg, the mites are already adults and the females lay the next generation of eggs. They multiply extremely fast given that each mite can lay an average of 50 eggs.
How do you tell if your marijuana plant has mites?
Microscopic mites are nearly imperceptible by the human eye, if not completely invisible. They can measure around 0.2 mm, so they are difficult to see even with a home microscope.
However, here are a few signs to help you detect whether you have mites in our marijuana plant:
- They are translucent, with a yellowish color, and they move very quickly.
- They are light sensitive, and therefore hide themselves in the middle of the plant, on recently grown branches and leaves, or even between buds where they will start to weave their web.
- White spots on the leaves or very tiny marks.
- Very fine webs under leaves and branches. We should suspect mites or some kind of small spider in our plants upon simply seeing a tiny transparent thread in the plant, and act quickly before they multiply.
- Yellowing leaves. If the plague is advanced, you’ll see that the leaves change color, which is a signal that it is losing chlorophyll, which gives all plants their green color. This can keep the plant from growing correctly, and in the worst of cases, kill it.
- Withered leaves and plant. You can see how the leaves wrinkle, deform, and become wavy.
- Brown colored pistils. Pistils oxidize and take on a brown color.
- Our marijuana plant and its flowers stop growing. The pest causes the plant to starve and leeches its strength to the point that it cannot develop correctly. You may see that it stalls and even shrinks. The pistils and trichomes get smaller and do not bloom new flowers.
How to prevent mites
At this point it is should be clear that prevention is better than cure. In terms of growing cannabis, it is much better to prevent mites from the first growing phases given that once our plant enters the flowering phase, and we have flowers and buds, our options are narrowed if the yield is destined for consumption.
Although you might think that it will never happen to you, it’s not worth risking when we have the option of applying a few simple practices:
- Reduce the temperature in your grow zone. Mites are comfortable in a warm, dry environment. Given that information, especially in indoor growing, we can play with the temperature without harming the plant, which also needs heat. You could consider reducing the temperature to below 20ºC.
- Organic compost and mulch for the soil. These will add in natural predators that will control mite invasion.
- Neem oil. This is a biological insecticide that prevents the occurrence of the red spider mite and other mites.
What to do if you already have mites: how to eliminate the red spider mite
Photographic Source: Cannabislandia
It is not recommendable to use insecticide after the plant has entered its flowering phase. Insecticides are extremely toxic, and they can harm the plant or the consumer, so we should consider what our best option might be given the state of the pest that we have and how our plant looks. A good option is to use biological insecticides and natural predators.
- Natural predators: These feed on mites and can help us to effectively solve the mite problem. One thing to keep in mind is that once the mites disappear, the natural predators are also going to look for a way to feed themselves. Amblyseius californicus are one of the most common but there are other insects that can help us achieve the same effect: Tisanópteros, Orius, Geocoris, Frankliniella occidentalis.
- Spray water on the plant. Water will destroy webs and also knock pests off the leaves, preventing them from feeding, which will help them to weaken and die. The important thing here is that we spray the plant with some degree of pressure so that the invaders are knocked off and our plan works, while still making sure that our plant suffers minimally and doesn’t undergo any breakage. We can use a hose that is pressure regulated or a low strength spray bottle.
- Vacuum the leaves. We can very carefully vacuum the plant in order to suck up mites and dump them far away from the plant.
- Chemical mite insecticide. If we are still in the growing phase, rather than the flowering phrase, or if the plant is not for consumption, we always have the option of a stronger chemical pesticide if the previous options haven’t worked and we see that the pest is getting worse. This option will eradicate the mites in their egg and larva stages in addition to adult and mature mites and microscopic mites.
- Natural products. You can try biological products that are not harmful for human consumption: Tansy infusion, garlic decoction, Dalmatian pyrethrum, etc.
- Eliminate the infected plant. If you have a grow situation with various marijuana plants and you see that the pest is really advanced in one of them, though it is sad, get rid of it. It might be worth it to sacrifice a small portion of your crop before it quickly infects the rest, one by one. Get rid of it, clear your conscience, clean the area well with bleach, and then try to care for the rest of the plants taking the previously mentioned preventative measures.
We hope that this guide helps you continue care for your cannabis plant.
You can also read other articles about pests, such as caterpillar pests, on our blog.