| Cephalosporium stripe, incited by Cephalosporium gramineum, declined with monoculture of moderately resistant winter wheat (Triticum aestivum L.) varieties. While disease declined for all varieties, decline was greater for the moderately resistant varieties Plainsman V, Newton, and Dodge. Disease incidence declined 70% for Plainsman V, 90% for Newton, and 85% for Dodge, but only 54-65% for Sturdy, Norkan, and Arkan. Normalization of data for yearly differences in the environment by expression as a percent of Sturdy, indicated decline was varietally dependent. Disease incidence dropped 13-14% for Arkan and Norkan, Plainsman V dropped 23%, but Dodge and Newton dropped 65% and 78%, respectively. These results help explain the observed decline of the disease in Kansas with the cultivation of Newton on the majority of hectarage.;Cephalosporium stripe decline apparently is not due to reduced inoculum production from infested residue produced by moderately resistant varieties nor high inoculum production from susceptible varieties. Newton, a variety that exhibited decline, produced more inoculum/g of straw and /g of sporulating straw, and more segments sporulated than that of Sturdy.;Winter wheat varieties were exposed to various rates of primary inoculum of Cephalosporium gramineum in the field. Disease increased with increasing rates of inoculum both years of the study. The susceptible variety Sturdy became severely diseased regardless of inoculum dose or environmental conditions while moderately resistant varieties did not show much disease during a non-conducive year. During a conducive season for disease, all varieties became highly diseased at high rates of inoculum, but Plainsman V, Dodge, and Newton suffered low levels of stripe at low rates of inoculum. Susceptible varieties should be avoided since they are sensitive to low inoculum levels and produce large amounts of infested residue. Moderately resistant varieties should be cultivated since they show low incidences of disease when exposed to low inoculum levels; such as would be encountered in commercial fields. Thus, the observed decline in disease with monoculture of moderately resistant varieties is likely due to their low sensitivity to low inoculum levels coupled with the low amount of infested residue that they produce. |
