Dung beetles (Coleoptera: Scarabaeidae and Geotrupidae) in North Carolina pasture ecosystem

by 1981- Lastro, Elina

LASTRO, ELINA. Dung Beetles (Coleoptera: Scarabaeidae and Geotrupidae) in North Carolina Pasture Ecosystem (Under the direction of D. Wes Watson). Dung beetles in families Scarabaeidae (subfamilies Aphodiinae, Scarabaeinae and Coprinae) and Geotrupidae (Geotrupinae) aid in the decomposition of dung providing many benefits to pasture and animal health. They improve the soil by burying nutrient-rich dung, and aerating and mixing the soil through tunneling activity. Dung beetles also compete with pestiferous flies and parasitic nematodes for dung resources. Recent trappings at two sites in North Carolina Piedmont and Coastal Plain regions revealed presence of 30 dung beetle species in cattle pastures. A survey of dung beetles was conducted from May to October 2005 in 10 counties representing the three geographic regions of North Carolina, the Mountains, Piedmont and the Coastal Plain. Total of 1,863 specimens representing 15 species were collected from dung baited pitfall traps or directly from cattle dung. Most commonly collected species were Aphodius pseudolividus Olivier and Onthophagus taurus Schreber. Elevation, temperature and soil type were taken into consideration when rationalizing the presence of certain species in the different regions of North Carolina. A study was conducted to evaluate benefits of O. taurus activity on soil nutrition and yield of two common North Carolina pasture grasses. Tunneling activity of O. taurus and dung burial for brood production elevated the levels of major plant nutrients P, K and N in three soil types (Piedmont clay, Coastal Plain sandy-loam and play sand) under laboratory conditions. O. taurus activity increased the yield of Sudangrass Sorghum bicolor (L.) and ryegrass Lolium multiflorum Lam. over the dung only treatment and control. Dung beetle presence improved ryegrass yield over the fertilizer treatment in Cecil red clay and play sand. Methoprene, an insect growth regulator successfully reduced the horn fly [Haematobia irritans (L.)] numbers in an area-wide program in Nash Co., NC. Dung beetle trappings in the treatment area revealed no significant reduction in the populations of several common species compared to the insecticide free control. Laboratory bioassay determined the effect of methoprene on the fecundity, survival and size of the most common North Carolina dung beetle species O. taurus.