Systemic Pesticides: Are Your Clones at Risk?

Departments - Upfront | Highlights

Failed pesticide tests might not be your fault, but they are your responsibility.

May 1, 2017

Eric Limon |

In the final days of 2016, Canadian licensed medical marijuana producer (LP) Organigram was rocked with a pesticide scandal: Batches of product made in 2016 tested positive for banned chemicals, including myclobutanil (a systemic pesticide that turns into hydrogen cyanide, a compound the Centers for Disease Control classifies as a chemical warfare agent, when burned).

The company issued a voluntary recall on Dec. 30 and expanded it less than two weeks later. An internal investigation into the matter yielded no conclusive evidence as to how these banned products made it into the cannabis, as Organigram was a certified organic cannabis producer. (The New Brunswick-based company had its certification suspended when news of the contamination broke.)

“The inquiry was thorough and was undertaken with the full cooperation and assistance of Health Canada and outside experts,” said Denis Arsenault, Organigram’s then CEO and now Executive Chairman, in a statement on Feb. 27.

How an LP, government authorities and outside experts were not able to find the source of the contamination is telling of the risks that come with systemic pesticides in the cannabis industry.

How They Work

Systemic pesticides are typically applied as a drench of the growing medium (soil, coco coir, peat moss with perlite, etc.) and are taken in by the plant through the roots, says Raymond Cloyd, a professor at the entomology department at Kansas State University, with specialties in horticultural entomology and plant protection.

When the roots take up the chemical, that active ingredient “moves through all the plant parts and, in some cases, it might move in the flowers, depending on the water solubility and general characteristics of that active ingredient,” Cloyd explains.

Myclobutanil is a common systemic fungicide and is used mainly to combat powdery mildew. Once applied to the growing medium, the main ingredient is moved through the plant’s water-conducting tissues (xylem) before being moved to the sugar-transporting tissues (phloem).

According to Cloyd, some of these systemic products may last up to 12 weeks in the plant’s system, which is why they have become a common part of horticulture and agriculture. He says their lasting effect makes them attractive because it “reduces the amount of input from spray applications.”

“However, there’s always an issue of getting into fruit or flower,” he continues, “and that’s why I don’t recommend them for fruits and vegetables, or any crop the fruit or the flower or, in the case of cannabis, the seed heads are going to be used for human inhalation or consumption.”

Low-Level vs. High-Level Contaminations

The very nature of systemic products and their absorption into the plant’s system poses a risk for cultivators who purchase and grow their crops from clones: Cuttings taken from a contaminated mother plant may also test positive for those chemicals.

Cloyd predicts that with herbaceous plants (such as cannabis), “if you applied a systemic insecticide … then a week later you take cuttings, depending on the solubility of the systemic ..., it probably would end up in those clones at some concentration.”

Reggie Gaudino is the vice president of scientific operations and director of intellectual property at Steep Hill Labs. His days are spent overseeing the genetic and quality testing at the cannabis testing company.
Photo courtesy of Steep Hill Labs

Steep Hill Labs, a California-based cannabis testing company, has been investigating pesticide issues in The Golden State. Following an outbreak of contaminated cannabis in California, Reggie Gaudino, vice president of scientific operations and director of intellectual property at Steep Hill, and his team met with growers who swore they never used pesticides, but had contaminated product. Following the thread, his team started testing clones bought from nurseries.

What they found: Pesticides are being used in various ways despite growers and nursery owners saying they were not using chemicals, according to Gaudino.

Steep Hill also discovered it could tell how the pesticide was applied based on the concentration levels and location of the contamination. For example, a low-level contamination in the plant with no contamination in the growing medium (soil or rockwool) would indicate the mother plant was treated with a pesticide, but the clone purchased by the cultivator was not in direct contact with the contaminant.

Likewise, a low-level contamination in both the plant and growing medium can indicate that people might be recycling contaminated soil, Gaudino says.

“Those are the ones that never have to use pesticides ... because you were reusing a constant low-level feed because the soil was already contaminated and, as we know, it sticks around for a while,” he says.

Gaudino says the company’s research has focused on the San Francisco Bay area where it tested more than 50 samples. While the original sample size was relatively small by scientific standards, the findings showed “an overwhelming majority of them had contamination on them,” he says, warranting further study into the matter. In fact, his team was recently approved to acquire clones from the Los Angeles area to start measuring how widespread this problem is.

Other Options

In addition to testing the clones before or immediately after you purchase them, Gaudino suggests an alternative way around this issue: to grow from seeds instead of clones.

“That would reduce [the risk] a lot,” he says. “You may still have a little stuff in [the seed coating], but you’re taking a little tiny seed” instead of a cutting from a contaminated mother plant. He also suggests always using new soil and growing materials.

If growing from seed is not possible, Cloyd suggests using beneficial insects instead of chemical pesticides to deal with pest problems. “We have a number of predatory mites that are very effective,” Cloyd says, “Phytoseiulus persimilis is a work horse. … There is a wide gamut of potential biologicals that could be used in a cannabis production system.”

Organigram, for its part, completely revisited its processes following its crisis. In a Feb. 27 press release, the LP announced it now tests all inputs before they are used (growing mediums, fertilizers, water, etc.), has added security cameras to areas that were not previously required to be monitored, and live-tests plants for pesticides and tests again before they head to market, among other changes. Through these steps, company officials are confident this type of situation will not happen again.