SUSCEPTIBILITY OF PINES IN SOUTH-AFRICA TO THE PITCH CANKER FUNGUS FUSARIUM-SUBGLUTINANS F SP PINI

Fusarium subglutinans f.sp. pini (F.s. pini) is the causal agent of pi tch canker of pines. The fungus has recently been found in South Afric a on the diseased roots of Pinus patula seedlings, but has as yet not been detected on mature trees in commercial forests. Inoculation of 1- year-old P. patula, P, elliottii and P. radiata seedlings with isolate s of F.s. pini resulted in canker development and shoot mortality. No significant differences in virulence were found among eight isolates o f the pathogen on P. elliottii and P. radiata, but isolate MRC 6214 wa s significantly more virulent on P. patula seedlings than MRC 6209. Di sease development was significantly more severe on P. patula and P. ra diata than on P. elliottii. Pathogenicity tests on 4-year-old P. patul a and P. elliottii trees yielded comparable results. Resinous cankers, similar to those described for pitch canker, developed on trees in th e vicinity of inoculation points but development ceased before stems w ere girdled.