Association of Pythium coloratum and Pythium sulcatum with cavity spot disease of carrots in Western Australia

El-Tarabily, K.A., Hardy, G.E.St.J. and Sivasithamparam, K. (1996) Association of Pythium coloratum and Pythium sulcatum with cavity spot disease of carrots in Western Australia. Plant Pathology, 45 (4). pp. 727-735.

Abstract

All 170 Pythium isolates from carrot cavity spot lesions from a field in Western Australia were found to belong to either P. coloratum or P. sulcatum. All isolates of P. coloratum produced large, brownish-black, water-soaked and depressed lesions on mature carrots inoculated with agar plugs colonized by the pathogen. In comparison, only a few isolates of P. sulcatum produced lesions and these were small. In glasshouse trials, P. coloratum produced substantial and numerous lesions at an inoculum density of 0.5% (weight of millet seed-based inoculum/weight of soil), whilst P. sulcatum produced few and small lesions at inoculum densities of 0.8 and 1% and none at 0.5%. This is the first record of P. coloratum as a causal agent of cavity spot of carrots.