Herbicide Screening in Industrial Hemp (Cannabis sativa L.) Production

Abstract

Lack of labeled herbicides for industrial hemp (Cannabis sativa L.) production in the U.S. accentuates urgency to identify herbicides for weed control. Weed competition reduced seed yield by 25 to 32%. Pre- and post-emergence herbicide experiments were conducted to evaluate hemp tolerance to herbicides and support efforts for herbicide registrations. For post-emergence herbicides, hemp response to clopyralid (105 g ae ha-1) and bromoxynil (280 g ae ha-1) exhibited the lowest phytotoxicity, up to 38%, with no reduction of yield compared with the hand-weeded check. Pre-emergence herbicides were more viable options because pendimethalin (1120 g ai ha-1), trifluralin (840 g ai ha-1), saflufenacil (38 g ai ha-1), and pyroxasulfone (109 g ai ha-1) resulted in less than 17% visible hemp injury and increased seed yield by 18 to 33% compared with the non-treated, weedy check.