While not all contamination has come from the cultivation stage, it is an ongoing concern among producers. An investigative journalism piece written in Denver back in 2015 called out multiple companies for pesticides, emphasizing the importance of finding more natural alternatives. There is a growing drive to find compliant, consumer-friendly, but affordable pest management solutions.
Integrated Pest Management (IPM), long used in other agricultural industries, is only just getting started among cannabis cultivators. The program approach uses “current, comprehensive information on the life cycles of pests and their interaction with the environment,” according to the US Environmental Protection Agency.
While not all IPM programs are organic, the approach is highly adaptable to organic strategies. The IPM approach sets parameters, monitors pest levels, puts preventative measures in place, and implements controls if necessary. All-natural methods steer away from pesticide use in favor of manual/mechanical interventions, companion planting, and predatory insect introduction.
The Potential of Companion Planting
Most IPM programs for cannabis thus far focus almost entirely on predatory insect pest management solutions. While affordable and appropriate for crops headed into medical markets, there are other solutions worth consideration. Outdoor cultivators, in particular, should plan to incorporate multiple preventive measures before any infestations reach problematic levels.
Companion planting is an organic IPM practice common elsewhere, but the cannabis industry (so far) has tended to ignore its potential. Companion planting is the practice of planting various species together for added benefits. There are several general benefits to companion planting, including for soil development, pollinator attraction, and more. Not all are necessarily the goal for companion planting with cannabis.
In cannabis, the goal of companion planting is to attract helpful predatory insects or to plant 'bait' species, which are more attractive to pests than the cannabis itself.
According to Russell Pace III, President of the Cannabis Horticultural Association, in “Companion planting for cannabis – examining the management of ecological habitats for beneficial insects,” this cultivation technique is all about the strategic creation of beneficial habitats. In his opinion, “Increasing the availability of flowers is often the single most important strategy for increasing the abundance and diversity of beneficial insects.” While cannabis does not require more pollinators (like other crops that rely on this practice), it does benefit from more insect predators and parasitoids, which depend on nectar and pollen.
Ground cover crops, with evergreen bloom cycles, are quite useful in outdoor cannabis fields. Pace suggests not only cover crop seed blends with continuous blooms, but also those with a variety of species to attract many different predator insects.
Determining the percent of space to dedicate to companion cropping is still a bit of an experiment in cannabis. Pace cites small trials that yielded benefits, with roughly 25 percent of the square footage covered with companion plants. He suggests growers experiment with anywhere from five to 50 percent of their acreage, using low growing cover crops.
Low-Tech Pest Management Considerations for Hemp
In 2019, US farmers were licensed to cultivate 511,442 acres of hemp, which is more than a 400 percent increase over the following year. As we head into 2020, the hemp acreage across the country will only continue to explode. With much of this crop feeding the CBD extraction industry, pest management solutions must be suitable for products destined for human consumption.
According to Entomology Today, with hemp cultivation essentially starting afresh, IPM strategies are far behind other cash crops. Thus far, corn earworm (Helicoverpa zea), Eurasian hemp borer (Grapholita delineana), hemp russet mite (Aculops cannibicola), and cannabis aphid (Phorodon cannabis) seem to be pests of most concern, but this may not hold true across the country.
Low-tech pest management solutions in the hemp industry are still under study, as there is not much hard data on which pests are causing the most economic impact. Furthermore, as cannabis sativa (including hemp varietals) produces THC as a defense mechanism, researchers are uncertain if infestation could alter the plant's natural THC level and potentially grow into an unusual plant.
With that said, two pest management options are appropriate in hemp cultivation, including the introduction of natural enemies and crop rotation. Manual/mechanical removal of pests, while appropriate, is not generally cost-effective.
The IPM Practitioner, Volume Volume XXXVI, from August 2018, suggests Bacillus thuringiensis (natural bacterial pest control) and biological controls such as Trichogramma, lacewings, and ladybugs for corn earworm. When it comes to borers, the guide suggests nematodes. For mites and aphids, they advise ladybugs and parasitoids.
Appropriate Low-Cost Pest Management Options for Cannabis
Cannabis plants end up in edibles, inhalables, extractions, and medical preparations. As such, cultivation practices need to avoid the use of any pesticides. Even organic options could leave residues not suitable for the human respiratory tract or medical applications.
Pest management approaches following organic IPM practices are the industry's best bet for keeping the consumer safe and limiting the risk of contamination. Although mechanical/manual removal of pests is not typically a low-cost option, companion planting and predatory insects are.
Both THC-rich and hemp varieties of cannabis are new industries, and much of the experimentation with IPM practices falls squarely on the shoulders of the cultivators. Organic, pesticide-free approaches to pest management may require a period of trial and error for the cultivator to find a solution that works for their crop, region, and specific concern. Yet, when IPM works, it facilitates compliant, organic, and clean harvests.
