Pacific Pests, Pathogens and Weeds - Online edition

Pacific Pests, Pathogens, Weeds & Pesticides

Citrus root & collar rot (264)

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  • Worldwide distribution. On bele (see Fact Sheet no. 149), citrus, papaya (see Fact Sheet no. 152), passionfruit (see Fact Sheet no.154), pineapple, tobacco, tomato (see Fact Sheet no. 157) and many other hosts. An important disease.
  • A water mould, an oomycete, not a fungus. Worse in wet soils. Root are infected and rot; collar rots occur causing the bark to dry, die and fall away, and the trunk to ooze gum.
  • Above-ground, leaves yellow, dry and fall, and branches dieback. Lower fruit become infected.
  • Cultural control: drainage; bud high on root stock; ensure nursery plants are disease free; weed; prune low-hanging branches; importantly, seek local advice on root stock varieties.
  • Chemical control: copper - against lower fruit infections and collar rots; phosphorous acid after times of flowering and main leaf flushes.
Common Name

Citrus root and collar rot, Phytophthora foot and root rot (Phytophthora nicotianae), and brown rot of citrus fruit (Phytophthora citrophthora).

Scientific Name

Two species are commonly found causing root and collar rots on citrus: Phytophthora nicotianae, and Phytophthora citrophthora.

AUTHOR Grahame Jackson
Information from Hardy S, et al. (2012) Impacts and management of flooding and waterlogging in citrus orchards. NSW Government Department of Primary Industries; and from CABI (2015) Phytophthora nicotianae (black shank) and Phytophthora citrophthora (brown rot of citrus fruit). Crop Protection Compendium. ( and Photo 1 Kohler F, et al. (1997) Diseases of cultivated crops in Pacific Island countries. South Pacific Commission. Pirie Printers Pty Limited, Canberra, Australia. Photo 2 Diseases of fruit crops in Australia (2009). Editors, Tony Cooke, et al. CSIRO Publishing.

Produced with support from the Australian Centre for International Agricultural Research under project PC/2010/090: Strengthening integrated crop management research in the Pacific Islands in support of sustainable intensification of high-value crop production, implemented by the University of Queensland and the Secretariat of the Pacific Community.

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