Doctor of Philosophy, The Ohio State University, 2003, Horticulture and Crop Science

Common groundsel (Senecio vulgaris L.) is an annual weed of Mediterranean origin that has become a worldwide pest in many crop production systems, including small fruit crops like strawberry. Management of common groundsel has been difficult because of its tolerance of many control measures and resistance to some herbicides, and because of inadequate or conflicting information about its biology. Studies were conducted in Ohio to determine the effect of common groundsel's maternal environment on seed dormancy, describe the pattern of seedling emergence and seed persistence, and to evaluate the response of common groundsel and strawberry to herbicides. Experiments were conducted using local seeds and seeds collected along a 700-km transect from Michigan to Kentucky. Freshly matured seeds collected from sites along this transect differed in germination response to temperature, but when plants from these sites were grown in a common environment the seeds responded uniformly to temperature. In growth chamber studies, seeds maturing on plants growing in cold short day conditions were mostly dormant whereas seeds produced on plants in warm long day conditions were mostly non-dormant. Changing temperature conditions from warm to cold increased seed dormancy, especially when the change occurred in early reproductive stages. The dormancy status of buried seeds varied throughout the year, mostly in response to soil temperature. Seedling emergence was limited by both rainfall and temperature but there was an interaction with tillage. A logistic regression model demonstrated that in tilled soil, emergence was stimulated by small amounts of rainfall, but in no-till conditions about ten-times as much rainfall is required to stimulate emergence. Nearly all buried seeds germinated or died during two years of burial in soil. In newly established strawberries, common groundsel was controlled with the herbicide sulfentrazone (N-[2,4-dichloro-5-[4-(difluoromethyl)-4,5-dihydro-3-methyl-5 (open full item for complete abstract)

Committee: Doohan Douglas (Advisor) Subjects: Agriculture, Agronomy