Effect of dicamba on reproductive development in corn and rice

Abstract

Abstract Research has been published regarding the effects of sublethal dicamba rates applied at different growth stages in soybean [Glycine max (L.) Merr.]; however, there is limited research on the effect of dicamba on reproductive growth in corn (Zea mays L.) and rice (Oryza sativa L.). Experiments were conducted in 2018 and 2019 to determine the potential consequences of dicamba exposure to reproductive stages of corn and rice. Dicamba was applied at 0.56, 5.6, 56, and 560 g ae ha–1, with a 1X rate being 560 g ae ha–1. Each rate was applied at three reproductive growth stages (corn: pretassel, tassel, and green silk; rice: late boot, panicle exertion, and anthesis). Visible injury to corn was negligible; however, rice treated with dicamba at 56 and 560 g ae ha–1 had noticeably greater injury (3 and 12%, respectively) relative to the nontreated. For rice, visible injury associated with dicamba at 56 and 560 g ae ha–1 appeared in the form of upright panicles, which reduced panicle weight and seeds per panicle, ultimately decreasing yields by 2,120 (22%) and 4,140 kg ha–1 (43%). A yield loss in corn could be detected only when dicamba was applied at 560 g ae ha–1 at the pretassel growth stage despite dicamba at 560 g ae ha–1 reducing seeds per row and total seeds per ear. With severe consequences being observed only at high dicamba rates, the threat of off‐target movement to corn and rice is far less severe than in soybean.