Phytophthora frigida Maseko, Coutinho & Wingfield was described in 2007 in South Africa causing collar and root rot on eucalyptus (Eucalyptus smithii R. T. Baker) and Acacia decurrens Willd. (Maseko et al., 2007). Alves et al. (2016) reported P. frigida causing gummosis on black wattle trees (Acacia mearnsii De Wild.) in southern Brazil. The symptoms are necrotic lesions with or without exudation, that are localized in the basal region of the trunk. In Brazil, besides P. frigida, gummosis has also been associated with P. nicotianae Breda de Haan and P. boehmeriae Sawada (Santos and Luz 2007, Santos et al. 2006). In South Africa, gummosis is associated with P. nicotianae, P. boehmeriae and P. meadii McRae (Roux and Wingfield 1997). Etymology: The name ‘frigida’ refers to the cold tolerance of this species.
P. frigida produces sporangia abundantly in 10% nonsterile soil extract when grown under constant light. Most sporangia have prominent papillae. Most isolates have persistent sporangia formed singly or in a loose sympodium. The sporangial shape is predominantly ovoid, although there are other shapes such as globose, ellipsoid, and obpyriform found in some isolates, including some distorted shapes. The dimensions of sporangia range from 29 to 71 × 20 to 53 μm (avg. 46 × 33 μm), with length-breadth ratios of 1.3 to 1.5 (avg. 1.4). P. frigida produces terminal or intercalary globose chlamydospores that measure 21 to 55 μm in diameter (avg. 32 μm). P. frigida is heterothallic. Oogonial diameters range from 22 to 37 μm (avg. 30 μm). Antheridia are amphigynous and oospores are globose, aplerotic, and 18 to 31 μm (avg. 24 μm) in diameter (Alves et al., 2016).