Illegal Pest Control by Cannabis Growers

By Patrick Cavanaugh Farm News Director

Big problems are arising in the cannabis growing areas of California.

John Fournier runs Acadia Regulatory Consulting in New York State. He on an EPA list of registration consultants. And because his company is high on the alphabetical list, he gets calls from cannabis growers in California who are looking for help in dealing with pests and diseases on their crops. Because cannabis production is federally illegal and the registered crop protection material products fall under federal guidelines, there are essentially few materials that growers can use.

“The biggest pressures for cannabis growers are powdery mildew, fungus gnats, and mites. If a grower had a bad spider mite outbreak, they would want to protect a super valuable investment. The question is, what are they willing to do to protect that investment? And in a situation like that, maybe you’ll go buy a miticide off the shelf somewhere,” Fournier said.

“As long as it’s not restricted use, anyone can buy it and use it on your crop. In that situation, that’s going to be a product that’s not approved for cannabis use on the state approved lists, difficult to control legally. There are also fungus gnats, which are a problem with plants that are overwatered.”

A lot of growing happens underground, and growers will have a soil mixture that is overwatered, which is one of the most common problems in cannabis.

“When the soil is overwatered, algae will start growing in the soil, and fungus gnats will find the crop and start feeding on the algae,” Fournier explained. “And then they’ll start feeding on the fine root hairs of the crop itself so they can actually kill the crop, if the outbreak is bad enough. Fungus gnats can be controlled by either an insecticide to kill the gnats, or you can use a biocide to kill the algae. Again, the materials must be registered for cannabis.”

According to Les Wright, Fresno County Agricultural Commissioner, illegal cannabis farms have been raided and officials have found empty containers of rodenticides, nematicides, insecticides, and miticides, all illegal for use on cannabis. “We always find illegal crop protection materials and many of them had labels in Spanish, most likely from Mexican syndicates.

Again, there are no conventional materials registered.

Now here’s the part where it gets dangerous. According to Fournier, “In states where recreational cannabis has been legalized, I have spoken to people who have said they’ve discovered through some means or another … dangerous levels of pesticide residues on cannabis, where a grower had obviously used hundreds of times more than the labeled rate of an insecticide to save their crop, and obviously this could be dangerous to consumers.”