Correspondence between Dingley and Brown re Colletotrichum pathogen of pine in Australia

Type: Caulicolous Fungi; Description: This forma specialis is morphologically identical to Colletotrichum acutatum but differs in its pathogenicity (see below under SIGNIFICANCE).

Distribution: Northland, Auckland, Waikato, Bay of Plenty, Taupo, Rangitikei, Wanganui, Gisborne, Nelson.; 1st Record: Gilmour (1965b: as Gloeosporium sp.).

Significance: Dingley & Gilmour (1972) found that isolates from lesions on seedlings of Pinus spp., identified according to morphological criteria as Colletotrichum acutatum, were pathogenic to Lupinus arboreus, L. angustifolius, Lathyrus odoratus, Pinus spp., and Vicia sativa. Isolates from the two Lupinus species growing with young P. radiata plants in the field infected P. radiata seedlings. Isolates from L. arboreus growing on sand dunes were not pathogenic to P. radiata, although they infected other legumes. Isolates from Lathyrus odoratus were pathogenic to legumes but not to pines. Isolates from ripe fruit rots were not pathogenic to either pines or legumes. Isolates from all sources caused ripe fruit rot. The forma specialis causes a serious disease known as ‘terminal crook’ in Pinus radiata seedlings. The disease is most common in young (<1 year old) seedlings but older seedlings are occasionally infected. There is no record of the disease developing in seedlings that have been planted out on a forest site. The fungus survives on plant debris in the nursery beds and conidia are dispersed by water splash. Conidia landing on terminal needles of young seedlings germinate and hyphae quickly penetrate the stem, usually killing immature tissue on one side only. Uninjured tissue continues to grow and the terminal shoot curves over, assuming the typical shepherd’s crook shape. Infected needles die and although apical growth slows down, diameter growth appears to be stimulated since the stem becomes thicker and stiffer than normal. Affected seedlings remain in a dormant state until one of the lateral buds on the upper stem develops and grows into a dominant leader. This recovery may occur in the same growing season if the initial infection is very early and there is no reinfection. Under warm, humid conditions the disease can spread very rapidly. Infected seedlings are usually not plantable, resulting in serious economic loss to the nursery.; Host(s): Lupinus angustifolius, L. arboreus, Pinus contorta, P. elliottii, P. muricata, P. nigra subsp. nigra, P. nigra subsp. laricio, P. pinaster, P. ponderosa, P. radiata.