Publication Date

Fall 2016

Advisor(s) - Committee Chair

Todd Willian (Director), Paul Woosley, and Becky Gilfillen

Degree Program

Department of Agriculture

Degree Type

Master of Science


Field studies were established in 2015 at Bowling Green and Lexington, KY to evaluate industrial hemp (Cannabis sativa) tolerance to various herbicides. Hemp was planted into conventionally tilled soils in mid to late June at a seeding rate of 39 kg/ha in Bowling Green and 22 kg/ha in Lexington. Five herbicide active ingredients were applied preemergence (PRE) the day of planting and six postemergence (POST) treatments were applied to 30 cm hemp with a CO2-backpack sprayer delivering 140 L/ha. Plots were 3.1 m wide by 6.1 m long and were sprayed with a 2.1 m boom sprayer leaving a 0.46 m visual check on either side of the sprayed area. A weed free check and a non-treated control were included and all treatments were replicated four times in a randomized complete block design.

Hemp phytotoxicity was evaluated at 14 days after treatment for both PREs and POSTs. Hemp above-ground biomass, weed above-ground biomass, and seed yield were also evaluated. PRE herbicides did not injure hemp as much as POST herbicides, especially at the Bowling Green location. Mesotrione was the most injurious PRE evaluated (> 90%) while bromoxynil and MSMA applications resulted in low phytotoxicity (< 15%). Above-ground biomass was higher in the PRE treated plots, with the exceptions of bromoxynil and MSMA. Weed above-ground biomass was higher in the POST treated plots with the exception of mesotrione. At Bowling Green, PRE herbicides resulted in comparable yields to the weed-free check, except mesotrione. Metolachlor increased seed yield compared to the weed-free check and MSMA and bromoxynil had comparable yields to the weed-free check at both locations. Results identified possible herbicides to include in a future integrated pest management weed control program for industrial hemp.


Agriculture | Biochemistry