How to Get Rid of Spider Mites on Cannabis Plants?

How to Get Rid of Spider Mites on Cannabis Plants?

Created: 06.12.2018

If there’s anything a cannabis grower is terrified of, it’s the myriad of pests that attack the plants. And talking of pests, most of them are easy to slay. As humans, we have control over almost all the pests troubling our plants, but there’s one pest that makes growers wet their pants with just a mention of its name.

Yep, you guessed it…spider mites. The most horrifying of all. The deadliest, stubborn pests that never leave once they find their way in. Once they invade the plants, there’s no way to get rid of them unless you’re super determined and match their vigor to counter-attack them. If you’re a victim of spider mites and have lost your precious buds, read on to know how to fight them.

What are Spider Mites?

Spider Mites are not your regular spiders although they come from the arachnid family. Unlike spiders that are usually harmless, these little bastards suck the plant juices, ultimately killing the plant. One of their biggest advantages is that they are extremely small to be noticed, and by the time you even realize something’s wrong, a full-blown infestation can ruin and kill everything you’ve worked so hard for.

Typically found on the underside of leaves, they spin webs all over the buds and leaves, making it impossible to save the plants. The webs are meant to protect themselves and their eggs from other natural predators, but the buds are rendered totally useless at the end of it all. As most growers prefer growing indoors, spider mites already have an advantage where you can’t spray anything with abandon.

How to Detect Spider Mites?

For beginners, it’s pretty tough to identify spider mites mostly because they are so tiny. The best way to avoid spider mites is by preventing them. As they say, prevention is better than cure, so keep an eye out for spider mites since it’s easy to get rid of them at the very beginning. Once they build an entire colony, though, your worst nightmares will come true. Therefore, the first step is to detect them early.

Scrutinize the leaves – Spider mites suck the plant’s sap. They leave small teeth marks that are tough to be seen, but you can use a microscope or a simple jeweler’s loupe to identify the damage. The leaves turn yellow, making it seem like a nutrient deficiency rather than a pest attack, but if you look carefully and see webs, then it’s none other than your friendly neighborhood spider mite paying you a visit.

Always check the undersides of the leaves. That’s where they usually hide. The leaves also turn silvery due to the webs on them. The leaves appear spotted with white dots, and that’s the sign of teeth marks.

Use a magnifying glass – If you want to be absolutely sure that the pests are indeed spider mites, place a paper below the plant and shake the plant. Usually, the mites fall down on the paper and you can confirm their presence with a magnifying glass.

After a while, the leaves will have a few webs on them. Within a week, you’ll see holes on the leaves, but you need to take action as soon as you see the leaves turning yellow. The plant may also start shedding leaves at this point. Seriously, don’t ignore these minute pests, because although they are small and seem harmless, they really aren’t.

Different types of Spider Mites 

To add to your misery, spider mites come in different colors, and some of them are even more dangerous than the others. The two-spotted mite with spots on the back is pale yellow in color.  It’s the biggest villain with the ability to destroy over 200 different species of plants, and most growers give up because it’s extremely hard to get rid of them.

How to Prevent Spider Mites?

Spider mites thrive in hot environments with high humidity. Therefore, keep temperatures pretty low and make their life difficult. It’s also a good idea to remove any plant debris from the grow room because mites are amazing at hiding and waiting. Natural predators like ladybugs work amazingly well when plants are outdoors.

Most spider mites come from gardens, so change clothes if you’re entering your grow room. It may seem like much, but it’s better to prevent them rather than tearing your hair later. Try not to touch clones or plants infested with spider mites since they may hitch a ride to your grow room.

Yep, they are really that clever! The two-spotted mite is almost impossible to kill unless you nuke your grow room, so be extremely careful. Check all plants if you’re moving them from your garden into the grow room. This applies not only to spider mites but to other pests as well. A magnifying glass is your best friend in this situation, so invest in a good one to kill mites as soon as they make an appearance!

Here’s a video detailing the life cycle of a spider mite:

How to Kill Spider Mites?

They are different ways to get rid of spider mites including organic and inorganic ways. It’s actually easy to kill them, but the problem is that they come back with a vengeance. It’s also important to get rid of the eggs. Spider mites have an amazing ability to reproduce faster than you can count them. Within a week, they can destroy an entire crop, so pay special attention to eggs on the soil.

They become immune to pesticides quickly, which is why it’s recommended that you repeat the process every single day. Also, a combination of several methods described here should be followed. Spray liquids only when the lights are off to prevent the leaves from burning.

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Before using any method, remove the infected leaves. It’s better to even remove infected plants that cannot be rescued since it gives other plants a better chance to survive. Don’t make the mistake of composting those leaves. Rather, just burn them.

Try to use these methods when your autoflowers are still in the vegetative stage since it’s extremely difficult to get rid of mites in the flowering stage. Mites don’t distinguish between photoperiod and autoflowering cannabis strains – they treat them equally. So, whether it’s a photoperiod or autoflowering strain, the damage should be controlled before the plant begins to flower.

Also, buds taste a little different if liquids are used on them. If you absolutely must use any of these methods during the flowering period, spray the buds and plants with plain water to get rid of the pesticides.

Organic Methods

Remember to use a combination of several methods described here. Also, spray liquids on plants only when the lights are off to prevent the leaves from burning.

Soap Water – This is perhaps the cheapest way to get rid of most pests but certainly not the most effective. Simply mix a drop or two of castile soap or any insecticidal soap with a liter of water and spray away. Spider mites tend to slip and fall due to the soap.

To be extra careful, wipe individual leaves with a moist towel soaked in soapy water. It’s best to repeat the process every day since this method isn’t as effective as other commercial products. Even the soil should be sprayed to kill all the eggs.

Neem Oil – The simplest way to kill mites is to use Neem Oil mixed with a little dish wash soap. You can get neem oil online or in your local store. All you need to do is follow the instructions; however, be careful not to kill the plants because it’s pretty strong. Start with minimal amounts until you’re sure the plants can handle it.

General Hydroponics Azamax – Safe and natural to use, growers swear by Azamax. The best part is that it doesn’t hurt the plants or roots but only targets gnarly mites, fungus gnats, aphids, thrips, and several other pests. Spray the leaves, stems and every part of the plant including the soil to kill the eggs. Repeat the process every other day even if the mites are gone because they usually come back stronger.

Spinosad – Another organic product, Spinosad is nothing but fermented bacteria that kills spider mites immediately. Safe to be used around pets and children, it can be mixed with fertilizers although it’s best to use any pesticide separately. Spinosad infects the pests’ nervous system, and unlike other pesticides that harm beneficial microbes in the soil, Spinosad is perfectly safe to use.

Essential Oils – Some essential oils like Rosemary and Cinnamon are particularly effective in getting rid of spider mites and other pests. As always, a little soap mixed in will work. Organic products are amazing but they should be used with care since the plants could get affected if the oil remains on the leaves.

Rubbing alcohol – Not exactly organic, but rubbing alcohol or isopropyl alcohol mixed with water can help. Prepare a 50:50 solution of alcohol: water and spray. Some growers use the alcohol directly without diluting it but that might do a number on the plants. Alcohol tends to evaporate pretty quickly so the plants are pretty safe.

If you’ve tried everything and it still doesn’t work, pesticides made with toxic chemicals may be the only route for you. But, remember to use such products with extreme caution because they aren’t safe around pets and children. Also, wear a mask while spraying since they are dangerous. Once you harvest the buds, spray the grow room with a bleach solution to prevent further attacks.