Plateau (imazapic) at 0.0175 kg ai/ha (0.0156 lb ai/A) to 0.14 kg ai/ha (0.125 lb ai/A) was applied the day after seed of annual phlox (Phlox drummondii), black-eyed susan (Rudbeckia hirta), blanketflower (Gaillardia pulchella), lanceleaf coreopsis (Coreopsis lanceolata), scarlet sage (Salvia coccinea), standing cypress (Ipomopsis rubra), and sundial lupine (Lupinus perennis), were sown on a commercial potting medium or a sandy field soil in plastic pots. All seed were from one commercial source, with additional seed of black-eyed susan, lanceleaf coreopsis, and blanketflower from a second source (Florida ecotype). At 28 days after treatment, slight stand thinning was observed on scarlet sage, blanketflower, and black-eyed susan but the major effect of Plateau was stunting on all species. Annual phlox was the most tolerant of Plateau, with only occasional slight stunting and no stand thinning even at the highest rate. Lanceleaf coreopsis and sundial lupine were slightly less tolerant, with scarlet sage, blanketflower, and black-eyed susan being the most susceptible. Planting medium frequently affected Plateau activity, with stunting usually greater in the commercial medium than in a sandy field soil. For the species in which there were two seed sources, seed source affected tolerance of black-eyed susan and lanceleaf coreopsis. The Florida ecotype of lanceleaf coreopsis was more sensitive to Plateau than the commercial source. For black-eyed susan, sensitivity to Plateau depended on the medium in which seedlings were growing. Results for blanketflower were inconclusive.

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Author notes

Florida Agricultural Expt. Station Journal Series No. R-08951. The authors are very appreciative of the technical assistance provided by John Zadakis.

2Associate Professor and Senior Biological Scientist, respectively.

3Professor, Department of Statistics, University of Florida, Gainesville, FL.