Disease History: 

Gummosis has occurred in black wattle plantations in Brazil for more than 40 years (Santos and Luz 2007). The etiology was resolved only recently, with the causal agents identified as Phytophthora nicotianae (Santos et al. 2005), P. boehmeriae (Santos et al. 2006) and P. frigida (Alves et al. 2016). In South Africa, this disease has been reported in black wattle by Zeiljemaker (1971) associated with P. nicotianae and by Roux and Wingfield (1997) associated with P. boehmeriae and P. meadii.

Symptoms of gummosis on black wattle (reproduced with permission Summa Phytopathologica and Tropical Plant Pathology, courtesy A. F. dos Santos).

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Impacts in the Forest: 

Gummosis by P. boehmeriae has a limited geographical distribution in black wattle production areas of the state of Rio Grande do Sul, in southern Brazil (Santos and Luz 2007) and South Africa.

Forest and Wildland Hosts and Symptoms: 

Gummosis caused by P. boehmeriae occurs in outbreaks in rainy years associated with strong and constant winds (Santos and Luz 2007). Black wattle plantations of Brazilian trees with gummosis caused by P. boehmeriae can be distinguished from those caused by P. frigida and P. nicotianae (Santos 2001, Santos and Luz 2007, Alves et al. 2016). Gummosis associated with P. frigida and P. nicotianae has lesions in the basal region of the trunk and does not exceed 1.5 m in height, while gummosis associated with P. boehmeriae produces lesions over the entire trunk reaching up to 10 m.

Host Latin Name Host Common Name Symptoms Habitat Region
Acacia mearnsii Black wattle Gummosis, Canker Plantations Brazil, South Africa
Boehmeria nivea Chinese grass, White ramie Leaf necrosis Agricultural setting Australia, China, Greece, Japan, South Africa, Taiwan
Broussonetia papyrifera Paper mulberry Leaf necrosis China
Cedrus deodara Deodar cedar China
Citrus spp. Citrus Fruit rot Agricultural setting Argentina, Australia, China
Eucalyptus pilularis Blackbutt Root rot Australia
Gossypium hirsutum Cotton Leaf necrosis, Root rot Agricultural setting China, Greece
Pinus patula Mexican yellow pine Root rot Plantations Australia