As the weather turns cold, plant eating bugs seek out warmer locales to feast on plants. When they find a nice, temperate grow room full of sweet sensimilla, it's like an all-you-can-eat buffet at a resort for them. Mites, thrips, white flies and other foliage-eating pests can set up camp very quickly in the absence of preventative controls. While there are a number of beneficial insects and other non-spray methods of pest control out there, simple canopy sprays are still a mainstay of most gardeners’ pest control programs. By using organic products such as plant based oils on a regular program of preventative sprays, growers can keep their crop completely free of pests and diseases without the need for harsh chemical controls.
When it comes to preventative spray controls, you should look for naturally derived products that break down quickly. Organic products can readily be identified by the presence of the OMRI logo. OMRI stands for Organic Materials Review Institute and they're the folks that define what is and isn't approved for use in organic production. Some would argue that “organic” does not always mean “safe” as there are many potent naturally occurring toxins. However, OMRI recognizes this and that's why very toxic but naturally occurring chemicals such as nicotine are not approved for use in organic crops. A nasty trend in the hydroponics industry of stores selling “behind the counter” agri-chemicals to uninformed gardeners has gotten out of control. Many of these products are quite toxic and can persist for months in plants. In response, the general sentiment towards sprays of any type has become taboo. But there's no reason to avoid the sprayer altogether – you just need to be thoughtful about what to put in it.
The most important consideration when using spray controls is to spray regularly and completely. It's very important to spray the tops and bottoms of every leaf, even in the back corner of the garden where it's hard to reach. Turn off or raise lights when spraying to avoid leaf burn. It is also imperative to be consistent with your sprays – I tell new growers to set a day per week to spray preventative controls as their “spray day”. Because these products break down quickly in the environment, they leave no residue in the crop but do need to be applied regularly. There's a big aversion among many growers to spraying, but if you choose your products carefully, there's no reason to be afraid of giving your plants a nice washing. At first, it may seem counter-intuitive to spray even when there are no pests, but if you want to grow crop after crop of clean, bug/mildew/chemical-free Cannabis, then you need to spray before you see a problem. Also, I've noticed a pattern among growers where they don't want to spray anything on their plants, but then when mites or mildew are devouring the crop, they panic and spray whatever will fix the problem before the whole crop is lost. Often, these last resorts are very toxic controls that should be avoided at all costs.
When did humidity become a bad word anyhow? It seems that everyone is terrified of having a grow room with any amount of humidity. I regularly hear of growers who keep their rooms as dry as possible in order to thwart powdery mildew. Unfortunately, powdery mildew has adapted to both dry and wet environments and will persist regardless of humidity if nothing else is done. Another common conception among growers is that you simply can't spray anything on plants once they have been “flipped” into flowering because the plants will mold if subjected to any amount of water on the flowers. First of all, there is no harm in getting the plants wet occasionally for the first month of flowering, regardless of variety. Most Cannabis varieties will perform well at any moderate humidity level from 40-60%. Avoid extended periods above 60% later in flowering for most hybrid and indica varieties. Sativas are originally adapted to tropical environments with looser flower structures that dry easily after a rain and resist molds. Indicas, however, can be susceptible to mold in environments that stay significantly humid in the last weeks of flowering. They're not going to mold in the third week of flowering because the premature flowering structures were sprayed with neem oil or Mildew Cure, nor will the product affect the smell of the buds. Plus, sprays only increase the humidity for a very brief period of time in most indoor grows. Fans, ventilation and/or de-humidification equipment all pull the moist air out of the space within minutes to a few hours. If the humidity goes up for an hour, even drastically, that is still not enough time to incubate a fungal disease like botrytis (bud mold). Molds need at least a day or two of constant humidity to begin to establish themselves. Plus, if the product that caused the temporary increase in humidity was cleaning up the plants and killing spores on the leaves and flower structures, you're fighting mold, not contributing to it.
If you're growing a pure indica variety with particularly dense colas, then you'll want your room particularly dry as the flower structures begin to swell. But all through veg and early flowering, you'll still want to keep them nice and clean so they can easily cruise through their final weeks of flowering without any bugs or disease.
While we're on the subject of fungal diseases, let me highlight the product Mildew Cure. The name of the product says it all – it's the best all around powdery mildew control you can get, but it kills and repels insects quite well also. Originally sold by JH Biotech as “GC-3”, this product was made into smaller garden sizes under the SaferGro label. It's very inexpensive, widely available at most hydro stores or online and, most importantly, it crushes powdery mildew. Made of botanical oils, primarily garlic oil (which you'll notice at first, but does dissipate quickly), it also has a small amount of sodium bicarbonate – baking soda – in it. This is an important little detail because powdery mildew likes to establish itself on leaves that are below 7 in pH. By raising the pH of a spray solution, it raises the pH of the leaf surface, which greatly inhibits powdery mildew from getting established. If mildew is a problem, you can also raise the pH of any pest control spray to help control mildew at the same time. Interestingly enough, there is a registered fungicide called KaliGreen that is sold for powdery mildew control. The active ingredient is simply potassium bicarbonate – the same white crystalline powder that Earth Juice sells as “Natural pH up”. That's why a tiny pinch of pH up in your pest sprays can help prevent mildew even when spraying other products for bugs.
In addition to being a good band name (I want tickets if you make it big), this category encompasses many products derived from the Neem tree with varying degrees of refinement done to process them. First, let's look at regular neem oil. Neem oil is one of the best additions to any preventative spray program. It's inexpensive and controls both bugs and fungal diseases on the leaves. The oil works via mechanical action to smother pests while other compounds in the oil exert several different modes of action on pests. The chemistry of neem oil is very insect-specific, with no toxicity to humans. In fact, many soaps, shampoos and other personal care products have been made from neem oil, highlighting its safety for people. When selecting neem oil, make sure you look at the active ingredients portion of the label for “clarified hydrophobic extract of neem oil”. Green Light makes a product called “Rose Defense”, which is a quality, clarified neem oil and is often available at hardware stores. These products are far superior to the raw, unfiltered neem oil made by Dyna-Gro (black lettering on white bottle), which I don't recommend unless you like chunky liquid products that clog sprayers (I mean, seriously, DynaGro? You can't run it through a simple filter at least? I don't even know why hydro stores carry that stuff - it just gives neem oil a bad name. If that's all you've used and you didn't like neem, try any other brand.)
For even more refined products, there are the “Aza's” as I call them. Azatrol, AzaMax, AzaDirect and a few other products that begin with “Aza” are all refined extracts of neem oil that have been standardized to have an exact concentration of the primary active compound in neem – azadirachtin. While more expensive than regular neem oil, these highly refined products are outstanding for controlling established pest populations. If you see any sign of bugs, these products are effective on pests while still being gentle on plants and people.
Spinosad, commonly available as Monterey Garden Insect Spray, is an organic insecticide derived from a soil bacteria. Apparently a scientist discovered the organism that produces spinosad, Saccharopolyspora spinosa, in an abandoned rum distillery while on vacation. Awesome as that is, it's even more awesome that this drunken bacteria produces a natural insecticide that is very effective on foliage pests. Even mites and thrips can be beaten with spinosad applications. Spinosad also has a small amount of what's called “translaminar” absorption, meaning that some of it can be absorbed through the top of a leaf surface into the leaf allowing it to be lethal to pests feeding on the opposite side of the leaf. Translaminar absorption also allows for a slightly prolonged window of activity, although spinosad breaks down very quickly in high light environments. For best results, apply just before the lights go out. Although spinosad has some rough similarities to products such as Avid (both are fermentation byproducts, both have translaminar activity), spinosad breaks down much faster and more completely than Avid with significantly less toxicity to humans at every stage. For instance, Avid is not approved for use on edible crops, but spinosad is. Also, spinosad is the ingested form of flea control for dogs, Comfortis, further demonstrating its safety for mammals. Spinosad breaks down into carbon, hydrogen, oxygen and nitrogen from both light and microbial activity within days of application. Avid has a residual of 28+ days in the plant. There's no need to apply toxic controls to medicinal plants – nature has furnished controls that kill bugs effectively without needing to apply toxic, long lasting chemical residues to our crops.
SucraSheild is the newest organic pesticide that I've seen used on Cannabis, and its results are very promising thus far. Derived from sugar, SucraSheild is an on-contact organic pesticide with little residual activity. It leaves a sweet, slightly pungent scent on the plants for a few hours. Growers have been reporting good success controlling mites with SucraShield where other controls have failed, due to its unique mode of action and lack of demonstrated resistance. It's also regularly sold out in the pint sizes and has been since it came out, so that may be another indication of its efficacy.
If you have caterpillars or leaf eating worms, get some Safer brand Caterpillar killer. While I appreciate the clever rhyming product name more than most, the word “killer” makes it sound like a more toxic product than it is. It does kill caterpillars, and so lives up to it's name, but it's made from a bacterium (Bacillus thuringiensis var. Kurstaki) whose toxicity is so specific to caterpillars, it has absolutely no effect on people or pets, so don't be afraid to spray this based on the scary name.
There are a number of new products out on the market that utilize plant extracts as natural insecticides. Some growers have reported using essential oils mixed with small amounts of biodegradable soap to help mix the oil with water. Dr. Bronners soaps work well for this purpose and several versions incorporate essential oils of their own. Peppermint, clove, rosemary, and other essential oils are all being regularly incorporated into more natural pest control products. While more research is needed to clearly define application rates for each product, these may be some of the most cost effective organic controls if blended directly from raw essential oils. Be cautious when applying essential oils – start with just a few drops to a ¼ tsp per gallon mixed with a few drops of natural soap to start with as they can be very potent. Test new mixtures on one plant before spraying a whole crop. Check out Eden's Garden online (edensgarden.com) for a large selection of pure essential oils. For information regarding the chemistry of essential oils and their active ingredients, look to Wikipedia or just Google. New research in this area comes out regularly.
When properly applied, these and other OMRI approved spray products can keep even stubborn pests from establishing on your crop. The keys are to spray consistently (weekly) and to switch up products each time you spray. Some products can also be combined such as the Mildew Cure and Spinosad, which makes a great combo spray. Always test new tank mixtures before applying on a large scale. Do not rely on one product repeatedly or you risk creating a pest population that is resistant to that control. If plants are consistently kept clean from veg through early flowering, navigating the final weeks of flowering should be much easier. If, however, something does make it into the garden late in flowering, don't be afraid to spray a safe product (you can't allow mites or mildew on medicine) and dry the plants out as quickly as you can. In a well ventilated grow room, this should happen very quickly anyhow. Again, a short spike in humidity isn't going to cause mold if the environment goes back to its set point within a few hours. Even Mildew Cure, which has a strong smell when applied, dissipates within a day leaving no change in taste or smell on the product. When armed with effective organic spray controls, gardeners can feel comfortable spraying before pest or disease issues get out of hand. This way the crop can be completely free of both bugs and harsh chemicals – nature's best medicine in its purest form.
- JK
(Growers Grove writer Jade Kine is a former greenhouse manager for the medical Cannabis industry with over a million plants worth of experience. He is also the founder of CannAcademy (www.CannAcademy.com), a trade school dedicated solely to horticultural training for growers. Got a grow question for Jade? Drop him a line at
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Complete bio and previous articles at www.JadeKine.com Facebook/Twitter: @JadeKine)
