Response of Industrial Hemp (Cannabis sativa L.) to Herbicides and Weed Control

Abstract

Industrial hemp is a continuously expanding crop; however, there has been limited research on its herbicide selectivity and weed control. Pendimethalin, s-metolachlor and aclonifen at 1137.5, 960 and 1800 g a.i. ha−1, respectively, were applied in field experiments in 2022 and 2023 in Greece to study the response of industrial hemp to pre-emergence (PRE) herbicides and record their efficacy on weeds. In 2023, each PRE herbicide was followed by the postemergence application of cycloxydim at 200 g a.i. ha−1 due to infestation of Sorghum halepense. In 2022, retardation in hemp growth was recorded by all PRE herbicide treatments, with there being a slight reduction in stand counts by pendimethalin and s-metolachlor and leaf yellowing by aclonifen in one the experiments. In 2023, no reductions in crop establishment and plant height were recorded, whereas leaf discoloration caused by aclonifen was less evident; cycloxydim did not affect hemp and perfectly controlled S. halepense. Despite the herbicide injury, hemp recovered and succeeded in higher biomass in both experiments at Thessaloniki and in higher seed production in the 2023 Thessaloniki experiment. This study showed that pendimethalin, s-metolachlor and aclonifen can be regarded as potential pre-emergence options with precautions in wet and light soils.