Type: Radicicolous Fungi; Description: Basidiomata pileate, centrally stipitate. Pileus 30–80 mm in diameter, olive buff to olive brown, sprinkled with very small dull brown scales at the centre, convex at first, becoming plane to shallow concave; flesh creamy white. Gills decurrent to almost sinuate, moderately crowded, creamy white becoming dull fawn. Stipe tapering towards the base, fawn above evanescent annulus, brown to dark purplish below, smooth or striate, solid, 40–70 mm long. Basidiospores ellipsoid to elongate-ellipsoid, 7–9 × 5–6 m, non-amyloid; spore print white.

Distribution: See Significance.; 1st Record: Stevenson (1964: as Armillariella novaezelandiae).

Significance: Causes extensive vine death in kiwifruit orchards, particularly in the vicinity of stumps of felled shelterbelt trees. In older records (Gilmour 1966a; Dingley 1969), Armillaria limonea and A. novaezelandiae were collectively referred to as Armillaria mellea, a European species not known from New Zealand. Most records of disease attributed to infection by Armillaria (clearly recognisable from the presence of rhizomorphs and fan-like mycelial sheets under bark) do not identify the species as it is not possible to do so in the absence of fruiting bodies. No distinction between the two species is made in the account that follows. Shaw et al. (1981) found no significant difference between them in terms of pathogenicity. Hood & Sandberg (1993), using a large number of isolates in pot tests, found that A. limonea was generally slightly less pathogenic to Pinus radiata than A. novaezelandiae. They also found considerable variability in pathogenicity between different isolates of the same species. Armillaria limonea and A. novaezelandiae are endemic in New Zealand, fruiting bodies and rhizomorphs of both species being common in indigenous forests. They are apparently unable to parasitise roots in podocarp/hardwood forests where there is no evidence of mortality caused by Armillaria spp. Parasitic attack has been reported in Nothofagus forests (Rawlings 1953). As the natural distribution of Armillaria spp. is restricted to forested areas, root disease caused by these species is a first rotation problem only in plantations established on former indigenous forest sites. In new Pinus radiata plantations established on such sites, mortality commences 3–6 months after planting and up to 10% of the trees may be killed in the first year. Mortality continues for about 10 years and may affect up to 50% over this period (Shaw & Calderon 1977). Trees older than 10 years are rarely killed but infection persists in a non-lethal, chronic form to the end of the rotation. From a country-wide survey, Self et al. (1998) found that 39% of plantation trees on formerly indigenous forest sites were chronically infected. Such trees are susceptible to windthrow and toppling and grow more slowly than uninfected trees. Estimates of volume loss attributable to Armillaria infection vary between 14–24% for individual trees (Shaw & Toes 1977) and 6–13% for a 28-year sawlog regime (MacKenzie 1987). Armillaria root disease is not a problem in first rotation Pinus radiata stands established on farmland or other sites that previously carried only herbaceous cover (Gilmour 1966a). Self et al. (1998) found that 4% of trees planted on herbaceous shrub sites were infected by Armillaria spp. There is considerable evidence to show that on such sites, stumps left when the first tree plantation crop is felled can be infected by basidiospores carried over long distances (Hood, Horner et al. 2002). Rhizomorphs are not produced for several years and thus there is little or no mortality in the second rotation crop. When rhizomorph production does occur, trees are older and have developed some resistance. Although there is no mortality, varying numbers of trees become chronically infected and there is a consequent loss of volume increment. Kimberley et al. (2002) estimated a volume loss of just over 2% in a 13-year-old second rotation stand where approximately 20% of trees carried non-lethal, chronic infection. The only proven eradicative control measure for armillaria root disease is the removal of stumps, which are the main source of inoculum (van der Pas & Hood 1984). Stumping is expensive and difficult to undertake on steep country and is rarely practiced. Application of fungicides to stumps or soil has not been effective (Shaw et al. 1980; van der Pas & Hood 1984). Inoculation of stumps with saprobic fungi immediately after felling to prevent colonisation by Armillaria spp. (Yang & Hood 1992) is being explored. ADDITIONAL REFERENCES: Hood (1989: review of armillaria root disease in New Zealand); van der Kamp & Hood (2002: infection process); Hood, Kimberley et al. (2002: influence of silviculture); Hood & Kimberley (2002: disease survey methods); Firth & Brownlie (2002: aerial disease assessment methods); Shaw & Kile 1991 (comprehensive world-wide review of species Armillaria and armillaria root disease).; Host(s): Actinidia deliciosa, Bambusa oldhamii, Beilschmiedia tawa, Casuarina cunninghamiana, Cortaderia fulvida, Dacrydium cupressinum, Fuchsia sp., Grevillea robusta, Griselinia littoralis, Hedycarya arborea, Knightia excelsa, Laurelia novae-zelandiae, Litsea calicaris, Meryta sinclairii, Nothofagus menziesii, Nothofagus sp., Pinus radiata, Pyracantha crenulata, Salix matsudana.

According to Singer (1969) this species was also collected in the Nothofagus forests of South America.

Pileus 3-8 cm diam., olive-buff to olive-brown, sprinkled at centre with very small dull brown scales, convex at first with a strongly down-rolled margin, becoming plane to shallow concave, moist when fresh with a conspicuously striate margin, drying matt; flesh creamy white. Gills decurrent to a most sinuate, creamy white becoming dull fawn, moderately crowded with many short members. Stipe 4-7 x 0.4-0.8 cm, fawn above evanescent ring, brown to dark purplish brown below, smooth or striate, tough, solid, bases swollen and united. Spores 8-9 x 5.5-6.5µm, non-amyloid rather thick-walled (Fig. 24). Spore print white.

In dense groups round standing dead broad-leaved trees, or on their fallen timber, Wellington Botanic Garden, 2.6.1949, Stevenson, Eastbourne, Wellington, 4.6.1949, Stevenson (type); Butterfly, 2.6.1958, Stevenson; Otari, 22.6.1958, Stevenson, Kapiti, 22.6.1958, M. Davidson.

Pileus 3-8 cm diam., olivaceo-bubalinus usque olivaceo-brunneus, medio squamis minimis obscure brunneis sparsus, primum convexus margine valde deflexo-revoluto, deinde planus usque leviter concavus, statu vivo humidus margine conspicue striato, siccitate obscurus; came cremeo-alba. Lamellae decurrentes usque fere sinuatae, cremeo-albae deinde obscure fulvae, modice confertae, lamellis brevibus multis. Stipes 4-7 x 0.4-0.8 cm, supra annulum evanescentem fulvus, infra brunneus usque fusco-purpureo-brunneus, laevis vel striatus, tenax, solidus, basibus tumidis atque coalitis. Sporae 8-9 x 5.5-6.5 µm, haud amyloideae, parietibus satis crassis; in cumulo albae.

Typus: Stevenson 629.