Disclaimer: The following material is written in the interests of education and harm reduction.


Common Growroom Pests – Identification, Prevention, and Cure

 Part 1: Pesticides and Cannabis

Pests in the grow room can ravage crops through damaging plants and spreading disease.


The following section covers common pests and discusses ways of dealing with them (prevention and cure).


Further, this article looks in depth at pesticide types and their use in medical marijuana production (the so-so, the ugly and the very ugly). Anyway, let’s get down to business.




Rule 1: Prevention Is Always Better than Cure: In order for insects/pests to enter the growroom they must invariably come in from outdoors. As indoor growers we, unlike field/outdoor growers, have the luxury of being able to create microenvironments that enable us to exclude insects of any kind.  Pests are vectors (transmitters) of diseases – Insecticides are inefficient in preventing plant viruses spread by pests because the time needed to kill the vector is longer than the time needed to inoculate the plant. For this reason it is imperative to keep pests out of the growroom. Use filters on inlet and exhaust fans to keep pests out of the growing environment, spray outdoor ornamental plants such as roses and houseplants to reduce infestation probability, and treat cuttings bought/sourced elsewhere before introducing them into the growing environment etc.


Rule 2: Cleanliness in next to godliness! Keep the growroom clean of water spills and organic debris (leaf matter etc). Always wash your hands before entering the growing environment, do not go into the growroom after working in the garden, keep pets out of the growroom etc. We’ll cover more on this later.


Rule 3: Identify pests early by utilizing proactive growroom practices Check/look closely every few days – at least once weekly – on top of and underside of leaves, place yellow sticky traps in the growing environment to identify the presence of pests early.


Rule 4: Never crack a nut with a sledgehammer. Avoid the use of chemical pesticides, using natural alternatives instead. All pests can be controlled or totally eradicated using natural, organic, and safe alternatives to chemical pesticides.


Rule 5: If using a chemical pesticide always adhere to minimum clearance times and double it. If sold something from under the hydro store counter, be sure that you know what it is you are purchasing. If the supplier fails to provide you with the appropriate safety and usage data, source this data elsewhere (ie. Google the “product name + label” to source information). If the supplier is unwilling or unable to tell you what it is that you are purchasing exercise your right to shop elsewhere.


Re the latter statement: Ie. Pesticides Sold Through the Hydroponics Retail Sector


The problem is that some sectors of the hydroponics industry have a “wild west” mentality about the sale and distribution of pesticides.


As an article in the Bay Citizen notes:




“Pesticides not meant for use on consumable crops are available in “grow” shops throughout the Bay Area – a bustling market in which toxic substances are sold over the counter in unmarked vials…




“State and federal laws dictate that pesticides should only be used on approved crops – which do not include pot – and that the pesticides must be sold in packaging that is labeled according to standards prescribed by the Environmental Protection Agency. It is illegal to sell pesticides without this label, which explains how to safely apply the substances…


Some novices confronting pest problems apply pesticides with a heavy hand, they said; posts in online cannabis forums include questions from growers confused about how much Avid to use.


“There’s a lack of guidance on how to properly use pesticides,” said one former grower who now works as a pest control specialist. “There’s just a lot of guessing going on and a lot of misuse.”


A spokesperson for the California Department of Pesticide Regulation said it is illegal to sell unlabeled pesticides or use them on pot, but was unable to confirm or deny the legality of selling Avid or Floramite over the counter.


“You’re talking about products that are being sold without labels,” said Veda Federighi, the department’s assistant director of external affairs. “Somebody can put anything in it.”


Avid and Floramite have a low toxicity to mammals, and have been legally used in Bay Area landscaping. But neither government regulators nor chemical companies have never evaluated these pesticides – or any others – for use on pot plants.




“You’re dealing with people that are buying and using it in an unregulated fashion.”


(Kate McLean on May 26, 2010,


[End Quote]


Obviously, it’s a complex situation and one that only enforces the need for the legalization and regulation cannabis. At the same time, opponents of medical cannabis have seized the opportunity to portray its quality in the worst possible light in order to suppress dispensaries that are legal in certain US states.


As a result, no federal and state regulatory protections are in place, and the cannabis products distributed by dispensaries are not subject to compulsory pesticide testing. Additionally, the Bay Citizen fails to mention the rampant use of pesticides on legal agricultural crops that are regularly purchased through US and other supermarkets.


Pesticide Use in Legal Crops vs. Pesticide Use in Med


The U.S. in 2006 and 2007, used approximately 1.1 billion pounds of pesticides accounting for 22% of the world total. For conventional pesticides which are used in the agricultural sector as well in industry, commercial, governmental and the home & garden sectors, the U.S. used at total of 857 million pounds, with the agricultural sector accounting for 80% of the conventional pesticide use total.1


In research conducted by Chensheng Lu et al (2010) forty-six elementary school age children from Georgia and Washington states participated in the study for two to three days. Their parents collected a total of 239 non-organic food samples.


Nearly one-fifth (20%) of the food samples measured had at least one pesticide. Of those, more than one-quarter (>5%) contained multiple pesticides in the same food sample. It was also found that many of the food items consumed by the children were also on the list of the most contaminated food commodities reported by the Environmental Working Group.2


Similarly, UK and EU data shows pesticide residues in over 40% (39-47%) of all supermarket purchased produce. 3


Compare this to med cannabis and so far we’re looking good!


For instance…


The Los Angeles City Attorney’s office found 5.25% of the cannabis samples tested from purchases made through Los Angeles dispensaries (3 out of 52 samples) to contain some pesticide residues. 4


Additionally, one Dutch study has shown traces of pesticides in cannabis samples; however, not at levels that are likely to cause harm. 5


Compare this to tobacco – a legal crop responsible for 5 million deaths every year.


In a memo to James E. Swauger, Ph.D. from the FDA, Center for Tobacco Products  (December 6, 2011) this is outlined:




“Section 907(a)(1)(B) of the FD&C Act establishes that:

Beginning 2 years after the date of enactment of the Family Smoking Prevention and Tobacco Control Act, a tobacco product manufacturer shall not use tobacco, including foreign grown tobacco, that contains a pesticide chemical residue that is at a level greater than is specified by any tolerance applicable under Federal law to domestically grown tobacco.”


(And then goes on to say)


“This special rule provides that, effective June 22, 2011, manufacturers cannot use any tobacco, whether domestically or foreign grown, that contains a pesticide chemical residue that exceeds any tolerance level established under Federal law that applies to domestically grown tobacco…the Food and Drug Administration (FDA) consulted with the U.S. Department of Agriculture (USDA) and U.S. Environmental Protection Agency (EPA). According to USDA and EPA, under their laws there are currently no established tolerance limits for pesticide chemical residues that apply to domestically grown tobacco. If such a tolerance is established, we plan to provide this information to tobacco product manufacturers.”6


[End Quote]


Skipping the bureaucratic double speak, what this really means is the EPA regulates the specific pesticides that may be used on tobacco and other crops and specifies how the pesticides may be used. It does not otherwise regulate residues of pesticides approved for use on tobacco.


For every other product treated with pesticides and consumed by people or animals, the government assesses the health consequences of the pesticides used, sets safe limits on pesticide residues and routinely tests residue levels to assure compliance. Tobacco products have largely managed to escape all three tiers of this system.


EPA has chosen not to assess the risk of either intermediate, or long-term exposure to pesticide residues in tobacco smoke because of the severity and quantity of health effects associated with the use of tobacco products themselves.


Hence, while much is known about the significant health risks of using tobacco products, limited information exists on the extent to which the use of pesticides on tobacco may increase the considerable health risks associated with tobacco use itself.


When compared to other crops, tobacco leaf has more surface to weight ratio and with excessive use of pesticides there is always a chance for accumulation of pesticide residues in the leaf.


More than 130 different pesticides are used worldwide for the production of tobacco, with approximately 25 compounds used on a regular basis. They belong to different chemical groups, such as organophosphates, carbamates, organochlorine and heterocyclic pesticides, nitro compounds, pyrethroids and amides. Many of these compounds can cause moderate to severe respiratory and neurological damage or act as genotoxic (capable of altering DNA) and carcinogenic agents, therefore increasing the health risks associated with smoking.


More than 25 million pounds of pesticides are used in tobacco production in the United States, and tobacco ranks sixth among all agricultural commodities in the amount of pesticides applied per acre.


While no US research could be found, Canadian research by J-C. Dillon et al (1980) analysed samples of human milk for DDT and DDE. A significant positive correlation was observed between cigarette smoking and the DDE content of human milk fat.7


Similar studies support this observation.8


This information indicates that tobacco smoking increases the risk of pesticide bioaccumulation in humans.


These are just some of the facts that the Bay Citizen article fails to note.




  1. EPA
  2. Chensheng Lu, Frank J. Schenck, Melanie A. Pearson, Jon W. Wong (2010) Assessing Children’s Dietary Pesticide Exposure: Direct Measurement 
of Pesticide Residues in 24-Hr Duplicate Food Samples
  3. Pesticide Residues Committee Quarterly and Annual Pesticide Monitoring Reports 1998-2003
  4. Don Duncan (2009) HYPERLINK
  5. McLaren, J et al (2008) Cannabis potency and contamination: a review of the literature
  6. Memo from Lawrence R. Deyton, M.S.P.H., M.D. Food and Drug Administration (FDA) Center for Tobacco Products  to James E. Swauger, Ph.D., DABT, Vice President, Regulatory Oversight,  R.J. Reynolds Tobacco Company (2011)
  7. J-C Dillon, G.B. Martin, H.T. O’Brien (1972) Pesticide residues in human milk
  8. Jensen AA, Slorach SA. 1991. Chemical Contaminants in Human Milk. Boston, MA:CRC Press.

The Problem


Marijuana is the world’s most widely consumed illicit drug, with anywhere from 125 million to 203 million people partaking annually.


Pesticide use is illegal on marijuana. According to Title 40 of the Code of Federal Regulations, the EPA must establish residue tolerances for pesticides on all crops, and since none have been established for marijuana, pesticides cannot be legally applied.


This said…


Pesticide products such as Avid and Floramite are often popular with large commercial cultivators. Large commercial cultivators are responsible for large amounts of commercially available street (black market) cannabis. As a result, many cannabis consumers are unwittingly purchasing potentially tainted cannabis throughout Oceania, North America, the UK, and Europe etc.


Four samples of blackmarket marijuana bought off the streets in Gaylord, Metro Detroit and Traverse City, contained pesticides upwards of 440 ppm of permethrin, 630 ppm of cypermethrin, and 485 ppm of beta-cyfluthrin. By comparison, for spinach, the U.S. Department of Agriculture (USDA) sets residual limits of permethrin at 20 ppm and beta-cyfluthrin at 6 ppm. The USDA limit for cypermethrin is 14 ppm.1


This information is hardly surprising. The illicit status of cannabis and the high profits associated to the cultivation and sale of cannabis creates a situation which doesn’t lend itself to a strong code of ethics amongst some cultivators. Due to this, even when cannabis growers are aware that pesticide products contain harmful actives some will choose to use them regardless. In short, only a reprobate would choose to use toxins without warning their clients/consumers that this is the case. This said, the cannabis culture, due to the illegal status of the “drug”, attracts more than its fair share of reprobates. Quid pro quo!


As one med grower pitched it to me some time ago, “ When faced with losing thousands of dollars in produce or using a pesticide what are you going to do?” In this case he was talking about Avid which he had used within 9 days of harvest. Undoubtedly, given research with hops where it is shown that Avid’s withholding period is 28 days and that 80% of the residues remain present upon drying, this so called “caregiver” had just produced and sold potentially immune system suppressing, neurotoxic medicine to unsuspecting consumers.


To date, while many med dispensaries test for potency and some for potentially harmful fungi there is yet to be a concerted effort to test for pesticide residues. This situation is now changing, due to pseudo legalization in States of the US, as more testing laboratories and some dispensaries have recognised such tests are of crucial importance and are now lobbying for testing of chemical adulterants in medical cannabis. These adulterants include Floramite, Avid, pyethoids/pyrethroids, organochlorines, organophosphates, systemic chemical PGRs and other commonly used toxins.


Pesticides and Combustion


In research conducted by The Werc Shop (Independent Laboratory) risk of pesticide exposure to medical cannabis patients was explored. A laboratory setup was constructed in which the mouthpiece of the smoking device was fixed to tubing leading to a cold trap containing an organic solvent at low temperature. Inhalations were simulated using a vacuum pump and timed valve. The settings were made such as to represent the smoking behaviour of a typical adult cannabis smoker. The material used for this study was a single batch of medical cannabis which was prepared for use by applying ~750μg of various pesticides, diluted in acetonitrile (all pesticides adjusted for purity) one at a time to 5 separate sample lots containing ~2.3g of cannabis in round bottomed flasks. The pesticides tested were Imidacloprid, Permethrin, Bifenthrin, Pyridaben, Cypermethrin, Indoxacarb, t-Fluvalinate, Deltamethrin, Carbaryl, Propiconazole, Acetamiprid, Dicofol, Diazinon, Malathion, Thiamethoxam, Tetramethrin, Bifenazate, and Tebuconazol.


The results found a relatively large difference in recovery of residues between the different pesticides. The authors concluded that this was due primarily to the stability of each compound and to what extent degradation occurs under combustion.


The relative recovery of pesticide residues in the smoke stream ranged from 11.4% – 95.0% recovery from the glass pipe, 10.6% – 71.9% from the Waterpipe without filters, and 0.3% – 20.4% from a Triple-Filtered Waterpipe with filters.


The authors noting:




“The recovery levels from the unfiltered devices were alarmingly high, demonstrating the resilience of pesticides to heat degradation.”


[End Quote]


Below are the findings of percent recovery of pesticide residues in would-be inhaled smoke stream pesticides.


 Download Original Paper – The Werc Shop Report (PDF 1.9meg)


  1. “”
  2. The Werc Shop (2012) Summary Report to Scientific Inhalations Regarding McFinn’s Triple-Filtered Waterpipe With Pesticides

Bongs and Vaporizors to Reduce Pesticide Exposure


The Werc Shop findings clearly demonstrates that triple water filtration bongs greatly reduce pesticides residues in combusted cannabis.


Additionally, laboratory studies by California NORML and MAPS have shown how vaporizers can efficiently transport cannabinoids without the risk of inhaling harmful toxins. These toxins that are present in marijuana are carcinogenic polynuclear aromatic hydrocarbons, which are key suspects in cigarette-related cancers. The study, conducted by Chemic Labs in Canton, Mass., tested vapors from cannabis heated in an herbal vaporizer known as the Volcano® (manufactured by Storz & Bickel GmbH&Co. KG, Tuttlingen, Germany and compared them to smoke produced by combusted marijuana.


In principle, vaporization offers medical cannabis patients the advantages of inhaled routes of administration: rapid onset, direct delivery into the bloodstream, ease of self-titration and concomitant avoidance of over- and under-dosage, while avoiding the respiratory disadvantages of smoking.


The vapors from the Volcano® were found to consist overwhelmingly of THC, the major active component in marijuana, whereas the combusted smoke contained over 100 other chemicals, including several polynuclear aromatic hydrocarbons (PAHs), carcinogenic toxins that are common in tobacco smoke. The respiratory hazards of marijuana and tobacco smoke are due to toxic byproducts of combustion, not the active ingredients in the plant, known as cannabinoids.


The study used a gas chromatograph mass spectrometer (GCMS) to examine the gas components of the vapor. The analysis showed that the Volcano® vapor was remarkably clean, consisting 95% of THC with traces of cannabinol (CBN), another cannabinoid. The remaining 5% consisted of small amounts of three other components: one suspected cannabinoid relative, one suspected PAH (Polycyclic Aromatic Hydrocarbon), and caryophyllene, a fragrant oil in cannabis and other plants. In contrast over 111 different components appeared in the gas of the combusted smoke, including a half dozen known PAHs. Non-cannabinoids accounted for as much as 88% of the total gas content of the smoke.1


Further research has been done on vaporisers as a delivery method. A laboratory study found that a vaporisation device provided an efficient and reproducible mode of delivery of THC.2A further pilot human laboratory study comparing a vaporiser to smoked cannabis found that the vaporiser was as effective as delivering THC but with little or no increase in carbon monoxide levels, a marker for toxins that may be generated by smoking.3



  1. Dale Gieringer, Joseph St. Laurent, Scott Goodrich (2004) Cannabis Vaporizer Combines Efficient Delivery of THC with Effective Suppression of Pyrolytic Compounds: Journal of Cannabis Therapeutics, Vol. 4(1) 2004
  2. Hazekamp, A., Ruhaak, R., Zuurman, L., van Gerven, J., Verpoorte, R. (2006), ‘Evaluation of a vaporizing device (volcano) for the pulmonary administration of tetrahydrocannabinol’, Journal of Pharmaceutical Sciences 95(6): 1308–1317.
  3. Abrams, D., Vizoso, H., Shade, S., Jay, C., Kelly, M., Benowitz, N. (2007), ‘Vaporization as a smokeless cannabis delivery system: a pilot study’, Clinical Pharmacology and Therapeutics, online publication, 11 April.


Pin It on Pinterest

Share This


Share this post with your friends!


Share this article with friends!