Wright (1890) recorded a white root rot in New Zealand attacking fruit trees and a number of other host plants. Massee (1896) described a new species, Rosellinia radiciperda, which he claimed to be the perithecial stage of this white root rot fungus. The type collection at the Royal Botanic Gardens, Kew, has been examined and material typical of this species has been collected. Ascospore cultures have been prepared and have been found to differ from those obtained from white root rot in Pinus sp. and Eucalyptus sp. at Rotoehu (Gilmour, 1966a). Pathogenicity tests were also carried out, and the ascospore cultures from R. radiciperda were found to be non-pathogenic (Gilmour, 1966a). Although this question needs further investigation, a number of cultures from plants infected with white root rot agree with overseas cultures of Dematophora necatrix (the conidial stage of Rosellinia necatrix), and these New Zealand records have been listed under this species. It occurs throughout the country and can at times be troublesome in orchards, nurseries, and plantations.

Type: Radicicolous Fungi; Description: On hosts: Mycelium on roots near the root collar white, felted, often with 1–2 mm long digitate protrusions. In cultures on 3% malt extract agar: white, felted, with areas of black, flat, mycelial crusts. Hyphae hyaline, smooth, with pear-shaped swellings adjacent to many, but not all septa. Fructifications not seen.

Distribution: Bay of Plenty, Taupo, Hawke’s Bay, Taranaki, Wanganui.; 1st Record: Birch (1937).

Notes: The fungus causing rosellinia root disease of Pinus radiata in localised areas of the North Island has traditionally been known as Rosellinia radiciperda. The name originated with Massee (1896). He had obtained cultures of a fungus causing a root disease of fruit trees planted on cleared indigenous forest sites in New Zealand and identified them as those of an anamorphic fungus, Dematophora necatrix R.Hartig. Later, he received a collection of stromatic ascomata from the base of a dead Malus ×domestica tree, which he named Rosellinia radiciperda. From hyphal characteristics, Massee (1896) maintained that R. radiciperda was the teleomorph of D. necatrix. According to Cunningham (1925a) there is no valid evidence to support this association. Zondag & Gilmour (1963) reported that C.Bassett (unpublished data) had compared cultures of the pathogen obtained from roots of diseased Pinus spp. with ascospore cultures of authenticated Rosellinia radiciperda from Beilschmiedia tawa and found that they were “in no way similar”. Petrini (2003) recorded that, apart from the type collection, all seven hosts of authenticated R. radiciperda in New Zealand were exclusively native to New Zealand. Rosellinia necatrix is not included by Petrini in her list of New Zealand species of Rosellinia although she reported that many of the anamorphic collections on exotic New Zealand hosts in the PDD herbarium “may be, indeed, R. necatrix”. Pennycook (1989) included all records of R. radiciperda, except those from B. tawa, under Rosellinia necatrix Berlese ex Prillieux. The pine pathogen is certainly not Rosellinia radiciperda. It may be R. necatrix, but in the absence of any fruiting structures, this cannot be determined. Despite numerous attempts at inducing fruiting, cultures of the fungus obtained at various times over the past 40 years in the New Zealand Forest Research Institute laboratory have obstinately remained sterile, with one exception of an unverified record of the production of Dematophora fructifications. ‘Rosellinia radiciperda’ has been recorded as a cause of root disease in fruit trees and many indigenous plants (Cunningham 1925a). It may or may not be the fungus recorded on exotic forest plantation trees. The account below describes the fungus known to forest pathologists as ‘Rosellinia radiciperda’; a name that has been maintained purely for convenience.

Significance: Recorded in Pinus radiata forests in the central North Island as the cause of mortality in young stands (areas of up to 0.5 ha) and in single trees. Symptoms are similar to those of magnesium deficiency (needles with bright yellow tips covering the entire crown). Infected trees decline in vigour and eventually die. It occurs in only a few forests, and is of minor economic importance. Laboratory experiments using artificially infected soil have shown that the fungus is a virulent pathogen of P. radiata (C.Bassett, unpublished results; M.A.Dick, unpublished results). Reasons for low virulence in the field are unknown.; Host(s): Chamaecyparis lawsoniana, Eucalyptus obliqua, E. regnans, Larix decidua, L. kaempferi, Pinus patula, P. radiata, P. strobus, Thuja plicata.

MATERIAL EXAMINED: NEW ZEALAND, North Island, Wellington Region, Wainuiomata Valley, in forest surrounding Wainuiomata Reservoir, on decaying stems and aerial roots of Freycinetia banksii, 7 May 1997, S.R. Whitton HKU(M)14078 (IFRD). NOTES: Rosellinia necatrix is characterised by ascomata that are tightly clustered together, short stipitate and surrounded by a well developed subiculum of Dematophora necatrix Hartig. The asci have a subapical apparatus 6.5–10 µm high, 5–6.5 µm upper width and 2.7–5.5 µm lower width. The ascospores are 30–47 × 5.5–8 µm, fusiform, brown, surrounded by a thin gelatinous sheath and have a germ slit 7–22 µm long (Petrini, 1992). Ascomatal morphology, especially the presence of a short stipe, the presence of copious anamorph surrounding the ascomatal base, and the asci and the ascomatal morphology and dimensions make placement of this specimen in R. necatrix appropriate. Ascospore size in this specimen is slightly longer than that described for R. necatrix by Francis (1985) and Petrini (1992); this is assumed to be due to natural variation.