Professional Marijuana Grower


Outdoor Cannabis Garden Pest Control

Posted January 18th, 2019 by Dustin Fraser in , ,

A truth that is always self-evident when growing cannabis is the importance of a well-rounded pest control program.  Agonizing attacks from multiple pests big and small are inherent in outdoor growing.  If pests are allowed to run unchecked, your crop will become an inviting place for them to eat, breed, and live out their lives, thereby leading to the devastation of plant loss or lowered yields.  Investing in a multi-faceted approach to pest control is like having an insurance plan for your garden.  Spending the time and money it takes to keep hostile pests away is a crucial step toward having a successful garden.

When establishing a working pest control program be sure to keep in mind that it needs to be done in a way that utilizes natural and organic products.  The end harvest and any subsequent products made from it will be intended, in some form or another, for human consumption.  For a high-performance outdoor cannabis garden to maintain any amount of integrity it first and foremost must be free of any chemical pesticides or insecticides that might have possible carcinogenic (cancer causing) properties.  This is a medicine that thousands of people rely on and the safety of the end user is of utmost importance.  Fortunately, there are an abundance of natural and organic pest/insect control products available on the market today.

Natural and organic pest control products are different from the chemical alternatives in one major way.  Because they are less toxic when compared to the chemical alternatives, many pests and insects can build up

immunities to natural and organic control products when the same product is used repeatedly.  This is not the case with chemical pesticides and insecticides which have the same result with every application, but they are potentially harmful to humans.  With this in mind, a proper natural and organic pest control program should be comprised of multiple products that are used in a rotating fashion.  Using several products, at least three to four for good measure, which change from application to application, will ensure that the targeted pests do not build up immunities to the individual active ingredients.  If the pests are unable to create the immunities, then the products should be effective with every application.

A successful multi-tiered approach to pest management should include some of the following products: biological components such as beneficial microorganisms, natural-based mild contact killers, and plant derived pesticide/insecticide compounds.  When these products are used in rotation they will help deter and prevent attacks from the majority of pests.  The following are some natural and organic pest control products that work well for outdoor cannabis plant protection and can be used in a simple week by week pest control program.


An efficient pest control program starts with a strong biological foundation.  Regular soil applications, at least once a month, of beneficial bacteria and fungi will help create a healthy, robust root zone (rhizosphere).  A root zone that is fortified with beneficial microorganisms will be much more resilient and resistant to attacks from harmful pests and other soil-borne diseases.  The initial application of beneficial bacteria and fungi should take place the first time the plants are transplanted and be followed up with consecutive applications done throughout the entire growing season.  Biologically active compost teas should be incorporated into this aspect of pest control as well.  Bi-weekly applications to the soil will help to reinforce the biological fortification of the root zone throughout the season.

Replenishing the beneficial microorganisms is an important step because some of the other components in a complete pest control program can be harmful to the soil microbes.  Though the other products are applied to the plant’s leaves it is still possible that some will run off and end up in the soil medium.  Applying supplemental beneficial bacteria and fungi will ensure that the root zone remains properly protected.  A healthy root zone will lead to a healthy plant that is strong enough to withstand life outdoors.  Similarly, foliar applications of the compost teas should be done at least once a month after the plants are transplanted into their final outdoor container.  This will create a healthy leaf surface environment that will be resistant to attacks from pests.

The main way that the biological component of a complete pest control program differs from the rest is that it generally does not kill any pests or insects.  Instead it provides a healthy foundation that allows the plant to be less susceptible to external attacks in the first place.  With that said, there are some biological products that are more aggressive than others.  Take for instance the soil bacteria Bacillus thuringiensis (BT).  This beneficial bacterium has the ability to act as a biological pesticide and effectively poison the insects that consume it.  BT can form protein crystals that contain an efficient insecticide compound.  After a pest consumes the crystals, the digestive enzyme protease breaks them down releasing the toxins from within.

There are several BT products available on the market today and most come in a liquid form that is safe, when mixed with water, to spray on the entire plant.  Other living creatures that can be beneficial to the protection of a cannabis plant through consuming smaller pests are ladybugs and praying mantises.  If you decide to

purchase either of these, keep in mind that there is no assurance that they will stay to protect the garden and not just go on their merry way.  You, as the grower, can also help defend against unwanted pests in the garden by keeping a close eye out and inspecting the plants on a regular basis.


Azadirachtin is a botanical insecticide/miticide that is effective on over 200 different types of insects and is of extremely low toxicity to humans and other mammals.  The organic azadirachtin compound is extracted from the seeds of the Neem tree (Azadirachta indica) and is readily biodegradable, causing no harm to the plant or its roots.  It works by entering the insect by being ingested or absorbed through the body and acts as a feeding inhibitor as well as a growth disruptor.  The pests will essentially starve to death while being unable to properly reproduce.  There are numerous types of azadirachtin products available to growers ranging from oil-based liquids to water soluble powders.  Many of these products are certified organic and OMRI listed, making it a safe and reliable addition to any pest control program.

Keeping complete efficacy and reliability in mind, it is often best to use a water soluble powdered form of azadirachtin, especially if you plan on doing several applications throughout the season.  Most liquid azadirachtin products are oil based and have relatively low levels of the active ingredient.  These products, when used at normal recommended rates, do not provide enough azadirachtin to properly exterminate the pests.  Instead the oils merely coat and suffocate the insects leaving those that survive to develop immunity to the azadirachtin compound which will likely be passed on to their offspring.  When this happens the product becomes ineffective and an obsolete component of the pest control program.

It does not help to use more than the recommended rate of the oil-based liquid products in an effort to raise the concentration levels of the azadirachtin. This will only result in a solution that has heavy amounts of the natural oil base.  Spraying this solution onto the foliage of the plants has the potential to coat or clog the leaf stomata and severely disrupt the highly important transpiration process (how the plant breathes). Higher concentrations can also burn leaf tissue. The best way to avoid this while still maintaining adequate levels of azadirachtin in the spray solution is by using the water soluble powdered version of the product.  The water soluble powder does not contain any natural oils.  The exclusion of the oils allows it to be mixed with water at higher concentrations.  The resulting solution will be more effective at eliminating the targeted pests while avoiding any potential harm to the plant’s transpiration process.


Pyrethrins are a class of organic compounds that are derived from the Chrysanthemum plant (Chrysanthemum cinerariifolium).  These compounds have insecticidal properties and attack the nervous system of the targeted pests, leading to a loss of motor coordination and paralysis.  Pyrethrins have been approved by the Environmental Protection Agency (EPA) for more insecticidal uses than any other botanical derived product and they are effective in the elimination of most types of insects.  When used properly they present almost no risk to humans and other mammals.  Their efficacy and low risk potential make pyrethrins the most commonly used botanical insecticide on the market.  There are synthetic versions of pyrethrins, called pyrethroids, which are also used as insecticides but are not organic or readily biodegradable.  With the health and safety of you and those who may consume your product in mind, the organic plant-derived pyrethrins should be the only type used.

As was the case with the azadirachtin, it is best to use a pyrethrin product that is of a higher percentage concentration of the active ingredient.  Most pyrethrin products available contain one- to two-percent of the active ingredient.  Though pyrethrins work reasonably well, the lower level concentrations bring with them the potential of inadequately poisoning the pests. This leaves room for them to possibly develop immunity to the product.  Though they are often hard to find at a normal growing supply store, the best organic pyrethrin products to use are those that are above five percent of the active ingredient.  When used at normal label rates these higher concentrations will effectively eliminate the pests and still remain safe to use.


Spinosyns are organic compounds created through the fermentation of the bacteria species Saccharopolyspora spinosa.  There are over 20 natural types of spinosyns but the two that are most known for their insecticidal properties are spinosyn A and spinosyn D.  These two forms are mixed together after fermentation to create the popular organic insecticide ingredient spinosad.  Spinosad is a component of many organically certified and OMRI listed insecticide products and presents little risk of toxicity to humans and other mammals.  Spinosyns and spinosad work best through ingestion by the pests but can also have a desired effect simply through contact.  The organic compounds in spinosad target the nicotinic acetylcholine receptors causing a severe disruption to the pest’s nervous system, leaving most dead within one to two days.  Like most natural insecticides or pesticides, spinosad works best on smaller insects and larvae, but is still able to eliminate larger bugs like caterpillars.  The best thing about spinosad is that it is not very effective on beneficial insects like predatory mites and will leave most of them alive to do their daily pest control duties.

Contact Killers

Natural and organic contact killers are a key component to rounding out a successful pest control program.  As the name implies, contact killers are proficient at eliminating nearly any pest or insect that it comes in contact with.  These types of products are known to target pests but they can also be effective at mitigating fungal attacks like powdery mildew.  There are even contact killers that are designed for use within the growing medium to counter soil pathogens like pythium or root rot.  The fact that contact killers work on nearly every insect/pest that they reach means it will also kill beneficial insects and soil microorganisms, so regular applications of supplemental microorganisms and compost tea are important to revitalize the life around the root zone.

Most natural and organic contact killers contain multiple ingredients that have different modes of action in terms of pest elimination efficacy and act as proficient non-chemical contact killers.  Most products will contain a low level of organic oils, such as garlic or soybean oil, which help spread the product over the plant’s foliage while at the same time trapping and suffocating the insects or pests.  They also tend to contain light acids, such as citric acid, that are harmless to humans and other mammals but have the ability to repel most pests.   Alcohol is also found in nearly all natural and organic contact killers.  It is included because of its ability to dehydrate the bodies of the pests and insects that it contacts which leads to almost certain death.  This is also very useful when battling fungal attacks like powdery mildew as these fungi thrive in high humidity environments.  The alcohol dries out the surface of the fungi and prevents it from further growth.  The alcohols evaporate relatively quickly and will not leave any trace residues.  Natural and organic contact killers can only eliminate the pests or insects that they touch so make sure to apply the product properly over the entire network of stems and foliage for best results.

These are just some of the many different natural and organic pest control products available to consumers.  The important thing to remember is that the true purpose of a natural and organic pest control program for a high-performance outdoor garden is prevention.  The best way to deal with potential pest problems is by not allowing them to occur in the first place.  When allowed to progress, a pest or disease issue can cause serious damage and can lead to insurmountable damage to the crop.  So your best course of action is to never allow any pests the opportunity to occupy the plants for an extended amount of time.

This preventative need is why a proper pest control program needs to be started early and should include a variety of products in rotation to avoid any possibility of the pests becoming immune.  Using three or four different natural and organic pesticide/insecticide products in conjunction with applications of a natural contact killer is an excellent approach.  Start the pest control process at the time of the first transplant from the propagation tray into the five- to 15-gallon fabric aeration containers.  The first application should be just the natural contact killer.  This will lower the possibility of bringing any unwanted pests into the greenhouse type structure that will house them until the final transplant outdoors.  Plants can be treated by spraying or even dipping the entire top portion of the young plant into the solution.  Use half the normal label rate for the first application.

When they are housed in the greenhouse spray the plants every two weeks.  Rotate from product to product with every bi-weekly application and have natural contact killer applications taking place in between each different product.  For example, if you are using azadirachtin, pyrethrins, spinosad, and a natural contact killer, then a bi-weekly pest control program would go like this:

Contact killer > azadiratchtin > contact killer > pyrethrins > contact killer > spinosad > contact killer > azadirachtin, and so forth.

The greenhouse environment is protected and the outdoor temperature may be cold enough that pests don’t multiply, so using application rates that are half the normal use rate should be fine.  After the plants are transplanted into their final outdoor containers start making weekly pest control applications using the same rotating technique described earlier.  From the first pest control treatment up until the last, weekly or bi-weekly soil applications of beneficial microbes and compost teas should be used to re-fortify the rooting zone. This type of a weekly pest control program should keep any pest and insect populations to an absolute minimum. The programs should be performed until just before harvest.  The products to be used should be low in oils, quick to naturally evaporate, and easily biodegradable so they won’t leave a lasting residue.  These characteristics, along with natural rains and rinsing off the crop with water a couple days before harvest, will help ensure that any traces of the natural and organic pest control products are eliminated from the plant surface before harvesting.

This article is an excerpt from Outdoor Performance Cannabis written by Dustin Fraser and published by High County Publishing. For more information visit

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