Anthracnose Fungi of Olives

Abstract

IN published reports on anthracnose disease of olives, mention is made of only one responsible organism, the fungus described by Almeida¹ as Gloeosporium olivarum. I have observed that the causal organism of olive anthracnose in South Africa differs greatly from European and American isolates in spore morphology and cultural characteristics. The spores from Portuguese and South African isolates are much narrower than those isolated in Italy and the United States. The South African fungus develops a pink pigment in the mycelium on potato dextrose agar, as does the Japanese² fungus; but isolates from Portugal, Italy and the United States have a grey to olive-green mycelium. The spores from the Italian isolates agree very closely with those of Colletotrichum gloeosporioides Penz., and as Ciccarone³ observed setæ in the fungus from olives it is very likely that the two are identical. Spores from a Californian⁴ isolate showed close agreement with the spores of Glomerella cingulata (Stonem.) Spauld. and v. Schrenk; they are as broad as, but decidedly shorter than, those of Colletotrichum gloeosporioides. The Italian and American isolates differ from the Portuguese and South African forms also in the method by which the conidia are produced. The latter fungi are characterized by the formation of abundant microspores on the mycelium, which are much smaller than the spores formed in the acervuli; in the former, spores are only sparingly formed on the mycelium and they are of about the same size as the acervular spores.