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Dealing with Spider Mites on Cannabis

Written by Ed Rushford Dec 14 2023

Spider mites are small pests that damage gardens and landscaping. They consume fruit trees, ornamental houseplants, vegetables, cannabis, and other common plants. If left unchecked, spider mites can reproduce rapidly and kill cannabis plants. Fortunately, you can use simple techniques to protect your cannabis plants from these destructive pests. Here’s what you should know about spider mite characteristics, risks, and removal strategies.

Understanding Spider Mites: What You Need to Know

Spider mites are cannabis pests that are part of the mite family. They’re related to ticks and spiders. These critters have two body segments, eight legs and come in different colors based on age and species, including green, orange, red, and yellow. Spider mite populations flourish in warm, dry environments, making them one of the most prevalent insect concerns farmers encounter while growing cannabis indoors and in greenhouses. The red species are usually known as red spiders.

In addition, some change colors throughout the year, while others are translucent. All spider mites are very small, 1/60 to 1/25 inch, and are typically identified by the silky webbing they spin on cannabis plants and the general damage they cause to foliage. The most common species, adult two-spotted spider mites, have eight legs roughly the size of a grain of sand or a pencil period.

Signs of Spider Mite Infestation on Cannabis Plants

Spider mite infestations can cause stunted growth and reduced yield in weed plants. Webbing is a common indicator of spider mite infestation on cannabis plants. To identify spider mites, look for these common signs:

How to spot spider mites on cannabis
How to spot spider mites on cannabis.
  1. Oval-shaped mites are slightly bristled and pale green as juveniles with distinct dark green spots as they mature.
  2. A set of piercing-sucking mouthparts that allows them to pierce plants and suck out sap.
  3. Round bodies and a pair of red eyespots near their head.
  4. Webs that are thicker than a spider’s between its leaves, stem, and branches.
  5. Leaves that turn yellow, wilt, and fall off near the webbing

The Dangers of Spider Mites for Cannabis Growth

Spider mites cause weed harm by puncturing the leaf cells and sucking all the nutrients. The weaker leaves begin to harm the entire plant. The plants’ growth slows as they try to share their nutrients with the mites. The crop droops as the buds struggle to reach their full size and maturity. If not addressed, the plant may perish from extended weakness. Ultimately, spider mite infestations can lead to stunted growth and reduced yield in cannabis plants. In addition, spider mites can develop resistance to pesticides, making control challenging.

Preventive Measures: How to Keep Spider Mites at Bay

Prevention is the initial step in treating a spider mite infestation. Your grow room environment is key. Maintain correct environmental conditions such as temperature, humidity, and ventilation. Here are some tips to make spider mites prevention second nature:

  1. Quarantine new cannabis clones: Wait 2-3 weeks before integrating new clones into your existing growing environment.
  2. Sanitize your clothes: Moving from a grow room with pests to a clean room is a great way to spread them. Before moving to the next grow room, the clothes you wear should be sanitized.
  3. Do frequents checks: Frequent checks by visual inspections should become a habit. Regularly scout for pests using a microscope. Throughout the vegetative and flower stages, look at the bottoms or undersides of the cannabis leaves.
  4. Stick to the ideal mix rates: Grower’s Ally formulas are highly effective on insecticide-resistant pests. Do not mix products at half strength. Treat the first indicator of a problem at the curative rate.

Safe and Effective Natural Remedies for Spider Mite Control

Here are some effective non-chemical ways to eliminate spider mites indoors and out.

  1. If you are growing cannabis outdoors, spray undersides of leaves using a garden hose.
  2. Indoor growers should wipe leaves with mild dish soap and water.
  3. Spritz with a diluted combination of neem or rosemary oil for indoor or outdoor plants.
  4. Dust diatomaceous earth on indoor and garden cannabis plants to dehydrate the spider mites.
  5. Utilize a natural miticide.

Integrated Pest Management: A Holistic Approach to Spider Mite Control

It may appear extreme, but you want to eliminate any chance that a possibly mite-infested plant can harm the rest of your foliage. Experts recommend separating indoor plants from the rest for several weeks and checking for signs of spider mites and other pests before introducing new purchases to the rest of your collection. In addition, ensure your cannabis plants are well-watered and fertilized. Excess nitrogen makes your weed plants more vulnerable to spider mites. Healthy cannabis plants are more resistant to pests and illnesses, but weaker or stressed plants are more vulnerable to issues.

Spider mites

Chemical Solutions: Pros and Cons of Pesticides for Spider Mites

Pesticides can be an efficient way to manage spider mites, but they have both advantages and disadvantages.

Pros of using pesticides for spider mites

  1. Effectiveness: Chemical insecticides can be efficient against spider mites, especially in severe infestations.
  2. Certain bio-pesticides derived from food components such as safflower and cottonseed oils have been discovered to be effective against two-spotted spider mites. These bio-pesticides function through physical features rather than chemical ones, minimizing the possibility of resistance in the targeted insect.
  3. Selective action: Some bio-pesticides have little impact on other mite species that normally prey on spider mites, allowing the natural predators to continue.

Cons of using pesticides for spider mites

  1. Resistance: Spider mites can develop resistance to chemical pesticides, necessitating the use of greater quantities or the development of new pesticides.
  2. Environmental impact: Chemical pesticides can be harmful to the environment and might also kill cannabis-beneficial insects.
  3. Cost and application: Pesticides can be expensive and difficult to apply.

Effective Ways to Boost Your Cannabis Plant’s Natural Defenses

Boosting the natural defenses of your cannabis plant involves a combination of good gardening practices, strategic stress application, and maintaining a healthy growing environment. Some of the successful ways to do so, include:

  1. Choose potent cannabis strains: Genetics plays a big role in cannabis potency. Choose a strain with high cannabinoid content that is suitable for your growing setup, local climate, and skills.
  2. Use high-quality soil: Healthy soil contains all the cannabis nutrients your plant requires to grow healthy. Use high-quality soil from day one1.
  3. Proper watering and feeding: Under and over-watering or feeding can stress the plant and affect its health.
  4. Manage temperature: Protect your cannabis plants from cold and heat stress.
  5. Avoid light burn and irregular light cycles: Too much light or irregular cycles can stress the plan.

The Role of Proper Ventilation in Spider Mite Prevention

High humidity and dusty conditions can favor spider mite infestations. Therefore, proper ventilation plays a crucial role in preventing spider mite infestations. Here’s how proper ventilation helps:

  1. Disrupts stable conditions: Spider mites thrive in stable conditions. Avoiding excessive fluctuations in temperature and humidity can help prevent an infestation.
  2. Prevents stagnant air: Ensuring proper ventilation and airflow discourages the buildup of stagnant air, which can create an environment conducive to spider mites.
  3. Increases humidity: In gardens and on small fruit trees, regular, forceful spraying of plants with water often will reduce spider mite numbers adequately. This is because mites are most active when the temperature is high but when humidity is low. Increasing the humidity around cannabis plants can break the mites’ lifecycle.
  4. Prevents egg hatching: In glasshouses or igloos, wetting the ground regularly will increase the ambient humidity, preventing the hatching of mite eggs.

Strategic Plant Placement: Maximizing Spider Mite Resistance

You can use two main strategies: plant resistance and placement to protect your plants from these spider mites. Plant resistance means choosing cannabis strains that have natural or bred-in resistance to spider mites, such as some Indica or Ruderalis (Gorilla Glue #4 Auto and Zkittlez Auto) varieties. Plant placement means arranging your cannabis plants to make them less attractive or accessible to spider mites, such as by intercropping them with other plants that repel or distract them or rotating them with different crops to break the mite life cycle. These methods can help you prevent spider mite infestations and save your harvest.

Creating an Unfavorable Environment for Spider Mites to Thrive

Spider mites flourish in dry environments with temperatures about 30 °C. Spider mites can become interior pests throughout the winter because of the dry and heated temperatures. You should increase room humidity, especially in the winter when the air in the house is dry. Use a room humidifier or sprinkle plants with a spray bottle regularly. You can also grow your cannabis plants in trays filled with stones and a tiny bit of water. Don’t let the pot’s bottom sit in standing water. In addition, when bringing potted plants into the home for the winter, be especially cautious. Examine the cannabis plants for spider mites and other pests.

The Importance of Regular Plant Inspections and Maintenance

Regularly inspect your cannabis plants for any indicators of spider mites or other pests. Early detection enables rapid response action and prevents extensive infestation. The spider mites can multiply and spread quickly, making it difficult to control an infestation once it becomes established.

Identifying Beneficial Insects That Can Help Control Spider Mites

It may come as a surprise, but certain helpful insects can help minimize a spider mite infestation. Predatory mites like Phytoseiulus persimilis and gall midges like Feltiella acarisuga will help keep the pests at bay. Natural predators like ladybugs (commercially available) can help control spider mite populations. Predatory mites make sense to utilize mostly in greenhouses or indoors, where spider mites eventually inflict the greatest harm.

Beneficial insects will stay in a confined space soon. Thus, it is important to note that, although labeled as “predatory,” the small helpers are not hazardous to people. Constructing a habitat in the garden or field where predatory mites will organically multiply makes sense. Pesticides should not be used to treat a spider mite infestation with helpful insects since they may harm the beneficial organisms.

Cleaning and Disinfecting Techniques to Prevent Spider Mite Spread

Spider mites can be introduced to cannabis plants through contaminated soil, equipment, or nearby infested plants. Here are some cleaning and disinfecting techniques to prevent their spread:

  1. Regular inspection and washing: Inspect your plants for signs of spider mites and wash them as needed.
  2. Use of rubbing alcohol: Spray a solution of 4 cups of water, and rubbing alcohol can be sprayed on your plants to kill spider mites.
  3. Neem oil or insecticidal soap: They can treat cannabis plants if necessary.
  4. Bleach solution: A solution of 1 tablespoon bleach to 1 gallon of 35°C pH balanced water can be used to clean and bleach all the growing room’s surfaces.
  5. Alcohol and water: A solution of 9 parts water to 1 part alcohol can kill spider mites on contact without harming the weed plant.

Remember, treating plants thoroughly and regularly for several weeks is important to eradicate spider mites completely. If only a few cannabis leaves are damaged, use a disinfected cutting tool to eliminate them, then treat the plant. If the infestation is heavy and most weed leaves are damaged, it might be time to discard the cannabis plant.

The Art of Pruning: Removing Spider Mite-Infested Cannabis Leaves

Prune any spider mite-infested leaves and stems, placing the cuttings in a plastic bag and disposing of them in the garbage rather than your compost (eggs can stay latent until the right hatching conditions occurs). If the entire weed plant has mites, or its health appears too far gone to recover, consider plucking it to prevent the infection from spreading to others.

Avoiding Spider Mite Infestations in Indoor Cannabis Cultivation

Understanding how to eliminate spider mites on indoor weed plants is simple since you have greater control over the atmosphere. To efficiently eradicate them, lower the temperature, enhance humidity, and promote air circulation.

  1. Remove the contaminated leaves and discard them away from the growing area.
  2. Gently water down the cannabis plants to remove any remaining mites and webs.
  3. Use your spider mite killer to get the job done. Insecticides that are safe and organic also assist. However, avoid spraying on the cannabis buds.
  4. Stop for almost a week, then repeat the procedure several times.
  5. Switch between treatments every three days to prevent them from becoming used to one.
  6. Introduce spider mite predators like ladybugs, lacewings, and minute pirate bugs. Use only therapies that will not hurt them.

Monitoring and Preventing Spider Mite Reinfestation

If you have good eyesight, you can see individual spider mites on the cannabis leaves as you tend your plants. However, because they are so small and like to reside on the undersides of leaves, you will most likely have to put in some effort to capture them before they cause severe harm. Noticing them before populations increase can simplify your life as a gardener because it can be difficult to obtain (or recover) total control after they’ve invaded a plant. Cannabis growers can also do the following practices:

  1. Flip a few leaves over regularly and use a hand lens to inspect the underside for eggs, immatures, or adults.
  2. Watch out for webbing on the undersides of leaves and blossoms and webbing that spans from leaf to leaf. And, of course, watch for white or yellow stippling on the leaves’ upper surfaces.
  3. Shake or tap leaves with stippling damage over a piece of white paper to see if you have these pests. Any insects on the cannabis leaves that land on the paper will be easier to detect.

Safely Harvesting Cannabis Plants Affected by Spider Mites

If spider mites are found on buds during harvest, it may be too late to save them. Mites prevent the buds from maturing correctly, causing them to remain small. As a result, it may impact the quality and potency. If the buds are not severely damaged, gently water them down or add mite predators. You may also spray a DIY spider mite killer that won’t interfere with the taste.

Ed Rushford

Ed Rushford’s impact on cannabis growing is undeniable. Though he tends to focus primarily on 2 areas, plant training techniques and dealing with disease, pests, and other problems, he has offered many insights into how cannabis plants live and grow. That’s not to say that Ed is unfamiliar with the complete life cycle of cannabis, from seed to harvest, but he uses his widespread knowledge to hone in on the minutia and niche areas of growing cannabis. Ed’s goal is to spread knowledge and allow for everyone to become better growers. About this Author

Ed Rushford

Ed Rushford’s impact on cannabis growing is undeniable. Though he tends to focus primarily on 2 areas, plant training techniques and dealing with disease, pests, and other problems, he has offered many insights into how cannabis plants live and grow. That’s not to say that Ed is unfamiliar with the complete life cycle of cannabis, from seed to harvest, but he uses his widespread knowledge to hone in on the minutia and niche areas of growing cannabis. Ed’s goal is to spread knowledge and allow for everyone to become better growers. About this Author

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