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Disease Note. Fungal Root Rot of Gerbera in Western Australia. W. Kaewruang, Soil Science and Plant Nutrition, The University of Western Australia, Nedlands 6009. K. Sivasithamparam, and G. E. Hardy. Soil Science and Plant Nutrition, The University of Western Australia, Nedlands 6009. Plant Dis. 71:1146. Accepted for publication 10 August 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-1146A. Root rot is common in gerbera (Gerbera jamesonii L.) grown as a
garden ornamental in Western Australia. Isolations made from rotted
roots yielded binucleate Rhizoctonia-like fungi (23% of all fungi
isolated), Fusarium oxysporum Schlecht. (16%), Rhizoctonia solani
Kuhn (13%), F. equiseti (Corda) Sacco (7%), F. solani (Mart.) Sacco
(6%), Cylindrocarpon destructans var. crassum (Wollenw.) C. Booth
(6%), and F. chlamydosporum Wollenw. & Reink. (4%). No
Phytophthora spp. (1) were isolated from affected garden plants despite
use of selective media and baiting methods. F. oxysporum was the most
pathogenic fungus in the noncompetitive environment of a blotter test
(100%, disease severity index) and in a glasshouse test with pasteurized
soil (42%) and possibly forms a complex with other fungi. F. equiseti
was as pathogenic (40%) as F. oxysporum in the glasshouse but less so
(29%) in the blotter test. F. solani, R. solani, and C. destructans were
highly pathogenic (100, 100, and 83%, respectively) in the blotter test
but only mildly pathogenic (25, 23, and 25%, respectively) in soil. The
binucleate Rhizoctonia-like fungi were weakly virulent to avirulent in
both environments. |