State regulators want to know what sort of chemicals marijuana growers apply to their crops. Scheduled to issue growing licenses in mid-August—less than five months away—the Washington State Liquor Control Board has reached out to industry professionals for real-world advice on what biocides local growers dust on their dope. In an e-mail sent last Friday, comptroller Mike Steenhout asked recipients to "provide a list of all pesticides or any other compounds that you would ever apply to a marijuana plant."

Why? State and federal law requires all commercial pesticides be registered for the specific crop on which they are used.

"If you are using a product for a crop that's not listed on the label, that's a misuse and a violation of the federal pesticide law," says Chad Schulze of the Environmental Protection Agency. "Not only do you need your [pesticides] registered for that crop, you need what's called a tolerance for that crop."

The only products approved for pot in this country "were registered to kill it as a weed," says Schulze.

With no pot-approved bug juice in the United States, regulators may require all legal pot to be pesticide-free. The Washington State Department of Agriculture has authority over pesticides in the state. "Just because it's approved on the federal level doesn't mean it can be used in Washington," says Joy Harkness, who staffs the state's Pesticide Help Desk. She explains that every product on the WSDA pesticide list is on the EPA list, but not vice versa.

"No pesticide use is technically legal on cannabis under federal law," says David Lampach from Steep Hill Lab, the lead testing lab for the state's new pot consulting team. That said, Steep Hill's website points to EPA tolerance limits for pesticides on hops, a cousin of the marijuana plant, which has more than 60 approved pesticides.

Can we really just look at the hops category when evaluating pot production? "Not at all," says Schulze from the EPA. "It really has to be specific to the crop you're using it on." So unless pesticide manufacturers hustle to add marijuana language to their labels, state regulators may be forced to require a pesticide-free pot industry.