Cannabis Product Testing

Avoid crop loss from test failures with a practical approach to prevent contamination.

Dry cannabis flowers and testing lab glassware

Cannabis and the derivatives from it are the subject to testing because of regulations that protect consumers from contaminants such as pesticides, solvents, microbial impurities, mycotoxins, heavy metals, and foreign matter.

“The best procedures to avoid cannabis product test failure is to prevent contamination from known sources, and use approved treatments for pests and diseases.”

Test failures not only prevent cannabis goods from reaching the market, but often require disposal of a crop or derivative by law, making the entire cultivation effort a waste of time and money.

A Part of Legalization

Cannabis growers face many laws and regulations that vary by location. As laws evolve, most include criteria for consumer protection like cannabis product labeling and product analysis. For both commercial production and private use, testing cannabis for chemical content and contaminants is now a standard operating procedure.

In regulated markets where cannabis is legal, product testing for contaminants is a part of cultivation operation and expense. However, like other consumable goods that may rely on a national set of criteria for testing, none exist in cannabis goods so each state has different rules and they change. As regulations evolve, there may be unrealistic standards in some locations, technical issues in some laboratories, labeling variances, rules that go too far and some that do not go far enough, and so on.


Despite the all the inconsistencies, tough standards, and technical issues that may challenge the effectiveness of testing or that may lead to erroneous results, successful marijuana cultivators recognize the need to work within their present system until standardization and accuracy make testing compliance better for growers, producers, and consumers across the board. More important, astute cannabis farmers realize the time to start planning for more stringent standards that are likely to come, is now.

Mandatory testing of all cannabis products is typically a part of the process once legal markets open and usually change over time. In California, now the largest legal market in the country, starting in January of 2018, cannabis producers had a six-month grace period to sell or dispose of all untested products before required testing began in July of 2018. Like in Colorado, where growers face new pesticide testing in an already-established marketplace, an added concern for growers is the cost associated with testing. With an expense that can vary from affordable to expensive across the country with serious consequences like product disposal as the result of a failed test, growers in those and other states understand that testing may be the biggest hurdle to jump over from a farm to the legal market.

Beyond the Headlines

Following the first mandatory testing of cannabis products in California, lead media stories ensued with reported failure rates of 18 percent. While that is a large number, when broken into product types, most failures were from variances on the labeled THC content of a manufactured product, like edibles and tinctures. For cultivators, roughly 90 percent of tested crops passed the rolled-out standards, according to data from the California State Bureau of Cannabis Control. 

From the initial testing, with continual improvement since, the focus of responsible growers in legal markets of California and elsewhere is producing a clean flower, using policies and procedures that ensure the safety and value of the consumable crop; here are some of the best and most practical ways they use.

1. Identify Causes of Test Failures

The absolute goal of any grower is to prevent crop contamination from unacceptable levels of pesticides, solvents, mold, and bacteria. Using “food safe” products, techniques, supplies, and conditions offers an ideal guide for growers who often will emulate what they can from food crop producers. Factors including the environment, nutrients, pesticides, irrigation water, grow media, handling methods, and even packaging all influences the chemistry of the plant material, so a good first step is to identify what is safe to use in cannabis cultivation and the sources of contamination to avoid.

Finding a good testing laboratory near you is a prudent way to learn what testing standards apply to your crop and what contaminants to prevent. 

As test results vary by region, find local results available to the public if you can and examine recent findings from your area to see how the samples of others passed or failed testing. If known, determine what factors or agents caused failure and compare the information with products in your own operation to make certain you are not using any pesticide, fertilizer, supplement, or additive not allowed or that causes or increases a risk of contamination. Then make sure your cultivation practices prevent contamination from pathogens like mold or bacteria.

2. Use a Safe List

In most areas where cannabis cultivation is legal in some way, regulators often provide a list of what is “safe” for use on and around marijuana plants grown for medical or recreational use. State government, agriculture commissioners, business organizations, industry groups, and grower associations also provide guidance with recommended nutrients and pesticides along with those that are unacceptable for use on cannabis for commercial production. As laws and regulations change, so does pertinent information about testing protocols, compounds, and levels safe for use, etc., so remaining informed about current requirements is critical for operational planning and purchasing.

"When it comes to assistance with fertilizers and pesticides that are safe and effective for your plants along with what local growers are using for testing compliance, there are numerous resources to look to for guidance. Your local grower organizations, agriculture commissioners, local plant nurseries, and hydroponic stores all offer advice for compliant cultivation and safe products to use."

Growers must also be attentive to the growing substrate to avoid any systemic contamination to plant tissues. Unless certain of previous use and exposure, soil testing before planting is a good idea and not an expensive proposition. Agronomy labs or your local agricultural agents are excellent resources for support with soil and growing media.

3. Minimize THE RISK OF Contamination

An ounce of prevention is truly worth a pound of cure when it comes to controlling pests and pathogens in cannabis cultivation, so facility management becomes the key. Preventing disease or sources of contamination like mold begins with good sanitation in the grow area, indoors or outdoors, but also continue through the harvest and storage of the finished flowers. Clean gloves are a necessity for most cultivation activities, but very important when handling plant material to protect the product integrity. 

Through the cutting, trimming, drying, and curing of the flowers, the crop must have protection from pests, and anything that could contribute to contamination; things like common cleaning agents, even excessive alcohol or hemp oil from trimming scissors should not contact any part of the plant material. In the prevention of mold from which there is no rescue, air movement is essential.

Proper light, ventilation, temperature, and humidity all play an integral part of a plan to prevent contamination by reducing harmful conditions, the danger of a decreased crop quality, or worse, a permanently contaminated flower that will not pass a test.

Dosatron® Model D14MZ2

4. Use the Proper Dosage

When plants are healthy, minimal treatments with reduced application rates become useful in the battle against contamination because the potential from any concentration or buildup beyond an acceptable level also decreases. Prevention followed by early identification of a pest problem with immediate treatment with the correct dosage of a safe product is the basis for an effective anti-contaminant regimen. 

In cannabis cultivation, proper product use, and application rates adjust according to the age or phase of the plant growth cycle. For example, tender clones require or tolerate lower doses of a spray or fertilizer than mature plants, while some products are harmful to flowers near harvest time. Carefully read and follow label directions to avoid issues. Also, an imperative task; use the right equipment that is immaculately clean for each application.

Using the exact recommended dosages of approved compounds followed by methodical application rates, and intervals prescribed by the manufacturer are good management of risks associated with contamination. Toxic buildup of compounds from over dosage, or applied too frequently, or reactions with other chemicals are often contributors to not only poor growth, but also weakened tissue, and subsequent disease. Just using an approved pesticide or fertilizer without a dosage or feeding schedule can put your crop at risk for contamination. If the acceptable level of an approved chemical is too high, simply from over dosage and excessive application, the results can be a test failure.

The same goes for fertilizers and nutritional additives. Use only what is safe to apply around food crops and approved or recommended for cannabis. Follow label instruction to the letter; the research by the manufacturer and the defined application rates for dry or liquid materials are accurate for good cultivation results without contamination issues.


Most auto-dosing systems utilized in cannabis cultivation are very reliable and require little maintenance, however lines and valves must be clean, with regular ratio calibration checks suggested by the system manufacturer. As automation improves accuracy, functionality, and efficiency in horticulture, consider systems as another step in preventing contamination issues in your plants and at your facilities.

Dosatron® offers entry-level models all the way up to highly sophisticated dosing equipment. (Model D14MZ2 pictured.) Determine water pressure and desired flow rates with additional features that you may need for model selection.

Some products describe dilution or mix rates in the Metric (or decimal) system or in the US standard system. While it is helpful to use measuring containers that include both, it is very important to use precise numbers with conversion formulas when mixing any materials for plant application; not only for optimal plant health, but to also avoid any issues with contamination that could hinder testing results.

• Fertile Pages offers Cannabis Cultivation Reference Charts with conversions and formulas; useful for measuring pesticides and fertilizers.

5. Stay Ahead of the Curve

Testing for potency of a product is a part of testing and of chief concern to the extraction, manufacturing, and retails sectors of the cannabis industry where exacting concentrations must match labeling, with little tolerances and narrow margins. While a cannabis farmer must be aware that testing includes an analysis of THC and CBD percentage concentrations, it is a measurement of a harvested crop and a value that a grower cannot precisely control or determine. The THC and CBD concentrations are often the key to crop value; however, the principle concern for a grower is on purity when it comes to testing; if a crop contains contaminants or substances at unacceptable levels, it becomes worthless, despite the THC or CBD levels.

"As new criteria for testing follow new regulations, the cost for testing and labeling raw and manufactured cannabis products continues to increase. Once a nominal cost of production just a few years ago, it is common for purity and potency testing to vary from economical to expensive (cost per batch) in California’s newly regulated legal market, for instance. Labeling compliance adds additional costs, along with stricter record-keeping requirements, including trace and tracking systems if required."

As regulations expand for testing, it is more likely to become even stricter in time as consumers and regulators look for more safety in cannabis products. Fortunately, there are various solutions to become compliant and seek modification of the rules where needed. Challenging lab results is an example of a change many growers would like to see that is not currently available in California testing rules. Involvement in the process and continual education on the subject will empower licensed growers to meet the demands of today’s testing requirements while preparing with sound foresight for tomorrow’s rules and expectations of the future. Armed with science and solid information, growers can play a big role in determining good law. 

With new legislation adapting to the emerging cannabis markets, it is important to be a voice with your opinion about testing and other crucial issues that may affect you through letters to regulators, support of trade groups, and participation in grower’s organizations. With cannabis legalization and expanding opportunities, your involvement is a wise direction to take for yourself and an industry on the road to mutual profit and success.