Preliminary Studies on Binucleate Turfgrass Pathogens That Resemble Rhizoctonia solani

Abstract

Isolates from turfgrass [Pao pratensis, Festuca arundinacea], showing various foliar symptoms in Nov., 1974, 1975 and 1976, resembled R. solani in hyphal and cultural morphology. A collection was made of similar isolates from various hosts. These isolates did not anastomose with R. solani testers in anastomosis groups 1-4. Eighteen isolates were binucleate and had dolipore septa. The perfect state was induced in 4 isolates; these isolates were identified as species of Ceratobasidium based on basidial morphology. The 18 isolates were tested for anastomosis with each other in all possible pair combinations and were separated into 4 anastomosis groups. On potato-dextrose agar (PDA), optimum growth temperature was 21-23.degree. C for 4 binucleate isolates from turfgrass and 28.degree. C for the remaining 14 isolates and R. solani. In greenhouse pathogenicity tests on pot-grown, seedling bentgrass [Agrostis spp.], R. solani from turfgrass was not active at 10.degree. C, but produced severe foliar blighting from 16-38.degree. C. Binucleate isolates from turfgrass in Pennsylvania and New York [USA] produced severe foliar blight at 10-27.degree. C, but were not pathogenic at higher temperatures. Binucleate isolates from hosts other than turfgrass, all from southern states [USA], produced foliar blighting at 21-38.degree. C, but were not active at 10-20.degree. C. Benomyl, chlorothalonil, RP26019, anilazine, PCNB [pentachloronitrobenzene] and chloroneb, tested in PDA for activity against 18 binucleate isolates, gave variable results. Of the 6 fungicides tested, chlorothalonil and chloroneb showed the greatest overall activity in reducing fungal growth.