Published online by Cambridge University Press: 12 June 2017
Greenhouse and field studies were conducted to characterize wild poinsettia growth response to imazaquin (140 g ai ha−1), fomesafen and acifluorfen (420 g ai ha−1), and chlorimuron (9 g ai ha−1) applied at 5 to 7 cm (POST1), 8 to 10 cm (POST2), and 15 to 20 cm (POST3). Based on reductions in weed height and lateral branch number 28 DAT, wild poinsettia was controlled more effectively in both greenhouse and field studies for all herbicides applied at POST1 than at POST3. In the greenhouse studies, reduction in wild poinsettia biomass with the herbicides 28 DAT was similar when applied at POST1 and POST2 and, with the exception of chlorimuron, was higher at POST2 than at POST3. In the field study, weed biomass reduction measured approximately 4 mo after herbicide application was higher for imazaquin, acifluorfen, and chlorimuron applied at POST2 than at POST1. Wild poinsettia biomass was reduced more with imazaquin applied at POST3 than at POST1. Increased lateral branch production, indicative of decreased weed control, was often manifested in higher seed production per plant. With application of all herbicides at POST3 seed production was equal to the untreated check.