May 21, 2016 8:45 AM

What You Should Know About Spider Mite Infestation in Your Marijuana Garden

If you have a marijuana garden and never faced problems with spider mites, then you may consider yourself a lucky person. These pests may contaminate both outdoor and indoor gardens and turn the growing process into a real headache.

Spider Mite Infestation in Your Marijuana Garden

Know your enemy: spider mite

Two-spotted spider mites (Tetranychus urticae) are quite small creatures, usually around 1/50 part of an inch in length (0.4 mm). It is not so easy to notice this pest, as they are even smaller than aphids (plant lice). Their semitransparent body is usually colored either green, yellowish orange, or even bright red. The color does not depend on the plants the mites infest. Mites may feed on all kind of plants, including fruit trees, vegetables, flowers, and marijuana as well.

A life cycle of a spider mite is a little bit shorter than two months. Depending on the temperature, a pest reaches maturity in 5-20 days; then it keeps on growing and breeding for another two or four weeks. A female spider mite can lay about 20 eggs every day and give life to as many as 200 new pests throughout its life. The eggs are barely visible, they are 0.14 mm in diameter, and are placed mostly on the undersides of leaves.

Once the new spider mites hatch out of the eggs, they prefer to stay on the undersides of leaves, but as the mite colony grows, they can expand all over the plant, covering leaves and branches with a web that eases their movement.

The mites' primary diet is plant sap they get out of the leaves by piercing the mesophyll tissue with their sharp, slender mouthparts. The parts of the plants where mites live eventually collapse and develop chlorotic spots.

The danger of infestation

It is always better to prevent an infestation than to try to handle the problem of a pandemic later. Spider mites spread all over quickly. Within a single week, the situation can get out of control. The consequences of mite infestation can be devastating; it can ruin all your plants. And then you may still need to invest additional money, time and efforts to get rid of the pests completely, so they do not hurt the next growing project as well.

You need to check the undersides of the leaves regularly, looking for small yellow or bronze dots. It is important to handle the infestation before switching your garden to flowering stage, as it may be too late to use most of the available sprays during the flowering. These sprays may contain some pesticide that can spoil the buds flavor and be bad for human health. Apart from this, using pesticides during flowering may induce phytotoxic reactions and significantly harm the plants.

So, if you do not want to cause more harm than good, be extra careful with choosing the right spray. We also recommend you to reduce the light intensity (you may simply raise the lamps up) after you use the spray. Be sure to look at the spay's label and read all directions on the package to find out how long the pesticides stay active. (Usually, it takes about 24 hours; after that you can return the lights to the previous position.)

In most cases, one spraying is not enough to get rid of the pests completely. Unfortunately, sprays are not effective against mite eggs, so it is advisable to remove the contaminated leaves completely and repeat the spraying after several days.

Getting rid of spider mites

You may find a wide range of miticides in any flower or garden supply store; most of these sprays are quite safe for use. Look for those that are approved for use on food crops (strawberry, lemons, apples, etc.). There might be some miticides that are cheaper or promise you faster results but are approved only for use on commercial ornamentals. They contain heavy pesticides that can damage your health once the marijuana is heated, so you had better avoid those products unless you are growing cannabis only for harvesting seeds and nothing else.

The effective miticides may come in different forms, such as soap, oil, or spray. Choose the ones that have potassium salts, neem seed extract, pyrethrins, herbal or vegetable oils as an active ingredient. In most cases this kind of products degrade completely after ten days, so you may be certain that no pesticides will contaminate your crops.

Miticides are usually contact killers, so the more even is the coverage, the better is the result. Pay special attention to the small plants and small leaves, try not to leave any parts of the plants untreated.

Unfortunately, spider mites can adapt rapidly to adverse conditions. After several sprayings of a certain miticide, the pests become immune to the treatment. We would recommend you to have two or three different miticides with a different active ingredient to use alternately.

Preventing spider mite infestation

As we said before, it is better to keep your garden under strict control and never let the pests infest the plants. Usually, it is enough to follow these simple rules of sanitation:

  • Quarantine plants and clones from outside sources
  • Put on clean clothes before entering the garden room
  • Periodically disinfect the floor and growing box
  • Remove dead leaves and parts that start to rot
  • Keep the room clean, do not let garbage pile-up
  • Provide good ventilation and filter the air
  • Regularly inspect the plants, especially the undersides of the leaves.

Some growers use insects to control spider mites. These insects are, in fact, also mites. They are friendly to plants as they eat spider mites instead of leaves. You can also use ladybugs for the same purpose, but take into account that they will likely attack your light system, and if you use HID lamps, they may die before killing the mites.

If you choose biological control of the spider mite infestation, you should also take into account that using sprays may be not the best idea as it may kill both the spider mites and predatory insects.

Whatever way of attacking spider mites you choose, be sure you got rid of all the dangerous insects and did not leave a single egg alive. Better be safe than sorry.

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