Identification, purification and morphology of a virus causing a disease of St. Augustine-grass (Stenotaphrum secundatum (Walt.) Kuntze

Abstract

A new mosaic disease, first observed in the Lower Rio Grande Valley in 1966, has become a limiting factor in the production, maintenance and establishment of St. Augustinegrass (Stenotaphrum secundatum)(Walt.) Kunzte in Texas. A symptom of the disease is a chlorotic mottling of the leaf blades. The mottling becomes progressively more severe until a general chlorotic appearance exists. The disease was named St. Augustine Decline (SAD). Sap extracted from diseased leaves of St. Augustinegrass was rubbed onto healthy leaves of St. Augustinegrass and disease symptoms appeared in approximately 21 days. Transmission failed when attempted through soil, grafts, root inoculations and when using southern chinch bugs Blissus insularis Barber and leafhoppers Carneocethola sagittifera Uhler. Results of the transmission study suggests the agent causing SAD is a mechanically transmissible virus and can be spread by contaminated equipment such as lawn mowers. Attempts were made to isolate fungal and bacterial organisms from diseased tissues. A bacterium was recovered, but it did not produce SAD symptoms in healthy St. augustinegrass plants inoclated with it..