Wednesday, November 7, 2007 - 11:45 AM
266-9

The Influence of Host Resistance and Nitrogen Levels on Leaf Spot of Bermudagrass.

Maria Tomaso-Peterson, Mississippi State University, Box 9655, Dept. of Entomology & Plant Pathology, Mississippi State, MS 39762

Seven seeded bermudagrass cultivars were established in field plots in 2005 to determine host resistance to Bipolaris leaf spot and to evaluate the influence of nitrogen on leaf spot development. The study was established as a 4 x 7 factoral arranged in a completely random design with three replications. During establishment, seedling plots of Savannah displayed significant levels of leaf spot, leaf blight and plant death. Establishment was significantly reduced in seedling stands of Yukon, Transcontinental and Arizona Common at 14 days after planting due to leaf spot disease as compared to Princess 77, Sahara and Riviera that displayed little or no leaf spot symptoms. In 2006, the cultivars were maintained at a height of 1.91 cm. Four nitrogen levels (0-, 24.7-, 48.4-, and 97.7-kg N/ha) were applied monthly throughout the growing season. Bipolaris leaf spot development was incited by a natural infestation of Bipolaris spp. Visual ratings of leaf spot severity were recorded monthly throughout the growing season to evaluate the effects of host resistance and nitrogen levels. There was not a significant cultivar by nitrogen interaction, indicating that nitrogen did not affect leaf spot severity within a bermudagrass cultivar. Bermudagrass cultivars however, were significantly different. Princess 77, Riviera, and Yukon had similar levels of leaf spot severity that were significantly less than Arizona Common, Sahara, Savannah, and Transcontinental. Based on these results, inherent levels of leaf spot resistance varies among seeded bermudagrass cultivars and leaf spot severity will be similar within a cultivar, regardless of the nitrogen rate applied on a monthly basis.