Lloyd Johnson - The Beginner's Guide to Growing Marijuana

Another alternative is horticultural oil, like neem oil, an extract from the neem tree. This is an excellent alternative to nonorganic compounds for controlling spider mites.

If you find spider mites on new plants or clones, you should realize that you are now a vector that can carry the spider mites along to your healthy crop. The best thing is to treat the infested plants, remove all your clothing and bag it for removal to a washing machine, and immediately shower or bathe yourself.

Neem oil should always be used in strengths recommended by the supplier; doubling up on the amount of oil may injure your plants. Neem oil should be applied during the day to ensure quicker evaporation, which will reduce your chances of damaging the plants. Plants that are noticeably under water stress should not be sprayed with oils.

Although all of these steps may seem like a lot of trouble, it is nothing compared to what you are faced with if you get spider mites established in your grow rooms.

Some growers think that chemical solutions to the spider mite problem are acceptable to use as long as they are used early on in the vegetative phase of the cannabis grow. Putting aside the human health implications of using chemicals on a consumable, the grower needs to understand spider mite control and not just blindly spray poisons.

Very few insecticides are effective for killing spider mites. Chemical control of spider mites generally involves pesticides that are specifically developed for spider mite control: miticides or acaricides. Because most miticides do not affect the spider mite eggs, a repeat application at ten- to fourteen-day intervals is needed for control of hatching eggs. Frequent applications of miticides help create resistant strains of spider mites, making their control even more troublesome.

Natural, and extremely effective, enemies of spider mites include small lady beetles, predatory mites, minute pirate bugs, big-eyed bugs, and predatory thrips. Spider mites, especially in an outdoor grow, usually only become problems when the use of insecticides destroy their natural enemies.

For example, carbaryl, commercially known as Sevin, devastates most spider mite natural enemies and can greatly contribute to spider mite outbreaks. Malathion, despite being advertised frequently as effective for mite control, can actually aggravate spider mite problems instead of preventing them. Systemic, or soil-applied insecticides like Marathon or Merit, both of which contain the chemical imidacloprid, have also caused spider mite outbreaks by eradicating all their natural predators.

Spider mites have many natural enemies that limit their numbers in gardens, especially when unharmed by pesticide sprays, but the most useful ones are mites in the Phytoseiidae family, which are predators of spider mites. In addition to naturally occurring predatory mites, some are produced commercially for release as biological controls.

The predatory mites most frequently available by mail order are Galendromus occidentalis , Phytoseiulus persimilis , Mesoseiulus longipes , and Neoseiulus californicus . These are quite successful in controlling spider mites in indoor cannabis grows; predatory mites often like the higher humidity of a cannabis grow room, which is helpful as spider mites do not tolerate humidity very well.

The predatory mite Phytoseiulus persimilis cleans up after itself. Once the spider mite population is gone, they feed on each other, decimating their own populations.

Metaseiulus occidentalis is another common predatory mite used to kill spider mites. It is an effective biological control only if temperatures are on average between 44°F and 89°F.

Phytoseiulus longipes is a variant of the Phytoseiulus persimilis mite brought in from Africa. It can stand warmer ambient temperatures than its North American cousins. P. longipes has quickly become the most popular biological spider mite control agent used by gardeners.

Most suppliers provide information regarding use of the predator mites that they carry, but as a general rule of thumb, predatory mites should be placed out at a count of at least twenty per plant. The predators have difficulty moving from plant to plant, so they need to be placed on each individual plant. You can place more if you like, depending on the state of your spider mite infestation. It is estimated that one predator mite can eat twenty spider mite eggs or five adult spider mites per day. Like many super-specialized biological controls, most of these predators will die once the food source (in this instance the spider mite colony) is fully depleted.

For information on where to buy these predators, write or call California Department of Pesticide Regulation, 1101 I Street, P.O. Box 4015, Sacramento, CA 95812-4015, (916) 324-4100, and ask for a free copy of their leaflet “Suppliers of Beneficial Organisms in North America,” or view the leaflet online at www.cdpr.ca.gov/docs/pestmgt/ipminov/bensuppl.htm.

Other insects feed on spider mites and provide high levels of natural control. One group of small, dark-colored lady beetles (also called ladybugs), Stethorus species, are known as the spider mite destroyers; they are extremely specialized predators of spider mites. Additionally, minute pirate bugs, big-eyed bugs (Geocoris species), and predatory thrips are important natural enemies that can help the outdoor cannabis grower should you accidently bring spider mites to your grow site.

Another nontoxic weapon in the battle against spider mites is the use of sticky traps. You can create them by smearing a sticky resin like Tanglefoot on pot edges or cardboard that is an attractant color like yellow. Some indoor growers have had success with this trapping strategy: smear cardboard panels with Tanglefoot, being careful not to touch it, or the plants, with your hands. As your fans rotate, the spider mites are blown off and stick on the Tanglefoot panel. You can also put Tanglefoot around air intakes to trap incoming spider mites looking for a home. Of course, you will still need to treat the plants for spider mite eggs, but reducing the adult population will help you gain control.

Spider mites prefer dry conditions (one reason they are so prevalent in the more arid areas of the United States), so properly managing the moisture level of your plants is critical to prevent an outbreak. Plants stressed by lack of water also produce changes in their chemistry that make them more nutritious to spider mites. Spider mites also feed more under dry conditions, as the lower humidity allows them to evaporate excess water they excrete.

The indoor grower of cannabis has more control over how humid the grow environment is kept and should provide an environment that is less hospitable to spider mites. Overall, the best treatment is extreme caution, close observation of the plants and the grow environment, and prevention before infestation.

Outdoor growers of cannabis have many trials and tribulations that the indoor grower never experiences. The outdoor grower will also enjoy some wonderful moments that the indoor grower misses out on by growing in controlled grow rooms. The time you spend outdoors with your plants will bring you much closer to nature.

In addition to the natural experience of outdoor gardening, there are other benefits to growing your cannabis outdoors. It will cost less, your yield should be larger and better tasting, and your carbon footprint will be smaller.