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

Master of Science, The Ohio State University, 2013, Horticulture and Crop Science

Brambles (raspberries and blackberries), are an important commercial crop in Ohio. There is a significant potential to expand the current acreage based on the state's natural advantages for growing this crop and the expanding demand for fruit. Inadequate weed control is the major problem limiting crop development, planting longevity, productivity and berry quality (Galletta et al. 1990; Barney and Finnerty, 1994). In bramble plantings the critical period to control weeds occurs mainly in spring (Welker and Smith, 1972). Few options are currently available to control weeds as needed, and mechanical weed control is limited by the shallow root system and perennial nature of this crop. Therefore it is essential for growers to maximize weed control using a complete program, to prevent the germination of weed seedlings and to eradicate the unending problem of established perennial weeds. Thus, the objectives of this research were to quantify the efficacy of flumioxazin, oryzalin, oxyfluorfen, pendimethalin, and terbacil on recently established bramble plants; and crop tolerance to clopyralid applications in established red raspberry plantings. Our results corroborated the importance of good weed control during the establishment year to ensure optimum yields of brambles. Raspberry plants recovered from clopyralid-induced injury and a yield affect was not detected, indicating that clopyralid applied after harvest is safe to be used in established raspberry to control Canada thistle. Our results also showed evidence of differing in sensitivity among bramble varieties to herbicides, being flumioxazin and oxyfluorfen consistently the most injurious. Terbacil, provided the higher yield of blackberry `Chester' in 2010 and 2011, and plants recovered sooner from initial injury.

Committee: Douglas Doohan Dr. (Committee Chair); Joseph Scheerens Dr. (Committee Member); Michael Ellis Dr. (Committee Member) Subjects: Agriculture; Horticulture