Bassett (1958), and Thulin, Will, and Bassett (1958) found Pythium spp. to be associated with damping-off of seedlings of conifers in nursery beds at State Forest Service nurseries. Pythium spp. were also found associated with pre-emergence rot of pea seedlings (Brien, Chamberlain, et al., 1955). Smith (1953) found a Pythium sp. among organisms associated with black root rot of strawberries. In the Te Kauwhata district in Auckland Province Atkinson (1953a) and Newhook (1957) found a Pythium sp. associated with discoloration in phloem tissue of pear trees, which showed a sudden wilt.

Type: Radicicolous Fungi; Description: Colonies on corn meal agar radiate, aerial mycelium sparse. Sporangia terminal or intercalary, globose to subglobose, 12–30 μm in diameter, or elliptical to limoniform, 15–35 × 6–27 μm. Oogonia terminal, globose to subglobose, 16–27 μm in diameter, smooth. Antheridia 1–6 per oogonium, mostly diclinous. Oospores aplerotic, 15–25 μm in diameter.

Distribution: Northland, Auckland, Waikato, Bay of Plenty, Taranaki, Rangitikei, Wanganui, Wellington, Hawkes Bay, Dunedin.; 1st Record: Kirk (1906).

Notes: This is a confused species. The following description is based on New Zealand isolates identified as ‘Pythium debaryanum auct. non Hesse’ (Robertson 1980).

Significance: Commonly isolated from diseased roots and damped-off seedlings (Robertson 1973a). Reported to be moderately pathogenic to roots of vegetable seedlings (Robertson 1976).; Host(s): Acacia sp., Adiantum sp., Chamaecyparis lawsoniana, Daphne odora, Dodonaea viscosa, Fuchsia ×hybrida, Ginkgo biloba, Hebe sp., Leucadendron sp., Ligustrum sp., Mahonia aquifolium, Malus ×domestica, Persea americana, Rosa multiflora.