PATHOGENICITY OF 3 FUSARIUM SPECIES ASSOCIATED WITH ASPARAGUS DECLINEIN SOUTH-AFRICA

Isolations were made from crown, root, and stem lesions of symptomatic U.C. 157 F2 asparagus plants and from soil debris sampled in a declin ing asparagus field. Fusarium oxysporum, F. proliferatum, and to a les ser extent F. solani were the three dominant fungi isolated. Isolates of each species were evaluated for pathogenicity by inoculating U.C. 1 57 F2 plants in a greenhouse assay and an in vitro agar-test-tube assa y. All three Fusarium spp. were pathogenic to asparagus, although they differed significantly in their disease-causing ability. In an in vit ro assay, F. proliferatum isolates had a mean disease rating class of 4 compared with a class 3 for F. oxysporum and 2 for F. solani, on a s cale of 1-5. Significant differences between F. proliferatum isolates were also detected. The high frequency of isolation and virulence of b oth F. oxysporum and F. proliferatum indicate that both species are im portant pathogens associated with asparagus decline in South Africa.