Thumbs Down On Drug War Weapon

Using fungal biological agents, or mycoherbicides, would be a dubious strategy for destroying plants that produce marijuana, cocaine, and heroin, according to a National Research Council report released on Nov. 30. The agents’ efficacy is unclear, and their use would have serious limitations, say the NRC panel members.

Their report examined an idea first raised in the late 1970s of developing toxic molds against cannabis, coca, and opium poppies. These crops are grown in countries including Afghanistan, Colombia, and Mexico to produce illicit drugs.

Mycoherbicides have been viewed as a potentially potent weapon in the worldwide war on illicit drugs. A decade ago, for instance, the U.S. government urged Colombia to develop a mycoherbicide against coca and opium poppy plants. Fungi-based agents may be better than chemical herbicides, advocates believe, because strains could be selected to act against a specific plant species or a few closely related species, the report says.

Others oppose these “Frankenstein fungi,” viewing them as biological or chemical warfare agents, says Sanho Tree, a fellow at the Institute for Policy Studies, a liberal think tank.

There isn’t enough scientific information to determine whether mycoherbicides would effectively control illicit drug crops, the NRC report says. Conducting more research won’t guarantee the development of effective mold-based agents for this purpose, it continues. Furthermore, using mycoherbicides could harm other plants, beneficial microorganisms, or animals, the panelists warn. Plus, farmers could take counteraction after their fields have been sprayed, such as fumigating the soil to kill the fungi, they note.

“The technology has some limitations,” Raghavan Charudattan, chairman of the NRC panel that produced the report, tells C&EN.

For example, because their target crops are high-value, these agents would have to be delivered at much higher risk than conventional pesticides. Growers of illicit crops would likely defend their fields by attacking the delivery aircraft, explains Charudattan, emeritus professor of plant pathology at the University of Florida. To protect the pilots, planes applying mycoherbicides would have to fly at higher altitudes than conventional crop dusters or helicopters, the report says.

Use of mycoherbicides in countries where illicit drug crops are grown might be governed by the Biological Weapons Convention, it adds.