Pot and the Pesticide Question

June 14, 2015

By Marjorie Haun | Watchdog Arena

Questions about pesticide application to marijuana plants in Colorado and potential pest contamination to other crops have revealed gaps in the agricultural knowledge surrounding the state’s burgeoning industry.

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NO CLEAR ANSWERS: After speaking with agriculture experts of Colorado, information on proper pesticide use for its new marijuana industry is lacking.

Prior to the 2012 passage of Colorado’s Amendment 64, which legalized recreational marijuana, its cultivation was allowed only in licensed medical marijuana operations. The marijuana plant, Cannabis Sativa, is currently classified as a noxious weed in many states.

A recent Denver Post article about the quarantining of hundreds of marijuana plants at a commercial facility due to the improper use and application of pesticides and fungicides, brought to light an issue that has received little or no attention from the general public.

According to the March 23 story:

The state of Colorado has long had “best practices” type of guidance for pesticide use by pot growers, but the state has yet to conclude work on implementing rules for pesticide use in the industry.

Agriculture regulators generally require pesticides to be used as labeled. But because there aren’t any pesticides labeled for use on marijuana, growers are asked to use pesticides labeled for “unspecified crops and/or plants.

Technically, marijuana is governed by Colorado Pesticide rules, as are other agricultural crops, but commercial producers of pesticides have not included marijuana (Cannabis Sativa) on the labels which list appropriate crops for application. In a statement to Watchdog Arena, Duane Sinning of the Colorado Department of Agriculture Plants Division explained:

Pesticides labels are registered for specific crops in specific states. Those labels are held by the private pesticide industry so state laws cannot change them. Products not specifically labeled for use on marijuana plants cannot legally be used on those plants. Out of some 13,000 chemical pesticides on the market, only about 200 of them contain labeling language broad enough to allow them to be used on marijuana plants.

It appears that many of the implications and potential hazards of marijuana pests and pesticides are unknown. Although industrial hemp crops have been studied and there is a body of knowledge regarding industrial hemp pests and pest control, it’s difficult to find credible sources for similar information addressing commercial marijuana crops.

The Colorado State University Extension Office is considered the go-to resource for agricultural information; however, when asked about existing research on marijuana pests and pesticides, Colorado State University’s Assistant Vice President for Research & Industry Partnerships Mark Wdowik told Watchdog Arena:

CSU may be able to provide information related to industrial hemp, but not marijuana.  Researchers from our agricultural college may be able to assist you with information about hemp cultivation.  If your questions are specific to marijuana, you will need to turn to individuals and entities external, and not related to, CSU.

The dearth of marijuana research in the area of crop pest-control, and federal prohibitions against its commercial growth and sale may account for the absence of marijuana-specific labeling in the agricultural pesticide industry.

The pests and various diseases which attack hemp plants—a plant almost identical to marijuana without the high levels of THC—are fairly well known. One of the most insidious is the Aspergillum mold, which, if inhaled, can cause severe pulmonary disease. Hemp flea beetles, spider mites, hemp borers, weevils, and whiteflies are just a few of many arthropods that attack industrial hemp plants.

What is less-known is how the pests and diseases which attack hemp’s close relative, marijuana, will affect other agricultural crops such as fruit orchards, corn, wheat, etc. Marijuana is relatively new to Colorado as an outdoor crop, and little information is available about how it will grow and possibly spread in various regions such as the high desert, plains and mountainous areas, or how it might be a vector for the spread of agricultural pests and disease.

The unknowns surrounding marijuana pests and pesticides are one facet of the controversy over a potential outdoor medical marijuana operation in the middle of Western Colorado’s prime peach orchards and vineyards. Kendra Williams, a peach grower from Palisade, Colo., summed up the issue for Watchdog Arena:

We, the peach growers, have to obtain spray licenses for applying pesticide to our crops.  We have no idea whether or not the pot growers will have the same regulations. Entire crops have been pulled out of this valley because they spread diseases and bugs to other crops. Nobody knows what will happen with marijuana growing right next to our peaches. The people voting to legalize marijuana put the cart before the horse and there are agricultural questions that haven’t been answered, and I’m afraid the farmers out here will have to pay the price.


This article was written by a contributor of Watchdog Arena, Franklin Center’s network of writers, bloggers, and citizen journalists.

Reposted on  6/11/15

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