Postemergence Prostrate Spurge (Chamaesyce prostrata) Control in Container-Grown Liriope

Abstract

Abstract Four experiments were conducted to evaluate herbicides for postemergence prostrate spurge (Chamaesyce prostrata (syn. Euphorbia prostrata)) control and tolerance of container-grown liriope (Liriope muscari). In Experiment 1, Manage, Image, Trimec Southern, and Roundup were applied at three rates each to single bib liners of ‘Big Blue’ liriope in 10.2 cm (4 in) pots. Pots were infested with prostrate spurge that were 1 to 2 cm (0.4 to 0.8 in) wide with no flower or seed structures. Only Roundup at 0.45 kg ai/ha (0.4 lb ai/A) provided effective postemergence spurge control (96%) and caused no short-term or long-term injury to ‘Big Blue’. In Experiment 2, Finale and Roundup were applied at three rates each to established ‘Big Blue’ in 3.8 liter (1 gal) containers. By 21 DAT, Finale at rates of 0.28 kg ai/ha (0.25 lb ai/A) or greater caused slight though significant injury to ‘Big Blue’ while Roundup caused no injury. No injury was observed on any plant at 60 DAT and the following spring, growth was similar among all treatments indicating no long-term effects. In Experiment 3, Finale and Roundup applications were made to recently divided liners of ‘Variegata’ liriope infested with mature spurge 17.0 to 20.1 cm (6.7 to 7.9 in) wide, which were flowering and seeding. Finale at 1.12 kg ai/ha (1.0 lb ai/A) and Roundup at 1.8 kg ai/ha (1.6 lb ai/A) provided effective spurge control (100 and 92.8%, respectively) and caused no short-term or long-term injury to ‘Variegata’. Lower rates were not effective in controlling mature spurge. In Experiment 4, Finale and Roundup were applied to recently divided liners of ‘Big Blue’ infested with mature spurge 23 to 31 cm (9.1 to 12.2 in) wide, which were flowering and seeding. At 21 DAT, Finale at 1.12 kg ai/ha (1 lb ai/A) and Roundup at 1.8 kg ai/ha (1.6 lb ai/A) provided 100% control, while lower rates of both herbicides provided poor control (14 to 85%). Both herbicides caused slight initial injury to ‘Big Blue’, however, injury was outgrown by 60 DAT and by the following spring all plants were similar in size and number of new bibs produced compared to non-treated controls.