Fungi Associated with Spring Dead Spot Reduces Freezing Resistance in Bermudagrass

Abstract

Although the effect of cold winters on the severity of bermudagrass (Cynodon dactylon Pers.) spring dead spot (SDS) has been studied, information is needed concerning the effect of infection by fungi associated with SDS on the host's freezing resistance. A-22 bermudagrass was inoculated with Leptosphaeria korrae J. Walker & A.M. Smith and Ophiospharella herpotricha (Fr.) J. Walker & A.M Smith. Differential thermal analysis was used to monitor exotherm temperatures of healthy and O. herpotricha- and L. korrae-infected A-22 bermudagrass at 10-day intervals during 90 days of acclimation in cold chambers. Healthy bermudagrass crowns supercooled to an average of -6.7C and fungi-infected crowns supercooled to an average of -4.8 and -4.4C, respectively. Healthy crown exotherm temperatures were significantly lower than those of fungi-infected bermudagrass crowns on all nine sampling dates. This result indicates that fungi-infected plants are more susceptible to cold damage.