Efficacy and cost of four plant-derived, natural herbicides for certified organic agriculture

Abstract

Weed management is the greatest production challenge for most certified organic farmers, with few herbicides allowed on organic farms. Here, we compared the efficacy and cost of handhoeing (MECH) with a control (no weed management) and four commercially available registered organic herbicides under United States Department of Agriculture organic standards in managing Canada thistle (Cirsium arvense (L.) Scop.) and total vegetative cover in two apple (Malus domestica Borkh.) orchards. The four herbicide treatments had the following active ingredients: capric and caprylic acid (CAP), d-limonene (LIM), acetic and citric acid (ACET), and clove and cinnamon oil (CIN). In separate greenhouse trials, Canada thistle response to CAP (at two concentrations), LIM, glyphosate (GLY), and MECH were also studied.