Phytophthora cactorum (to be redescribed 2022)

Name and publication

Phytophthora cactorum (Lebert & Cohn) Schröter (1886)

Schröter J. 1886. pp. 129–256 (236). In: F. Cohn, Kryptogamen-Flora von Schlesien. Band 3, Heft 3, Pilze J.U. Kern's Verlag, Breslau, 1889, pp. 1–814.


from Schroeter (1886)




≡ Peronospora cactorum Lebert & Cohn, Beiträge zur Biologie der Pflanzen 1: 182 (1872) [MB166699]
≡ Nozemia cactorum (Lebert & Cohn) Pethybr., Scientific Proceedings of the Royal Dublin Society 13: 566 (1913) [MB562134]
≡ Phloeophthora cactorum (Lebert & Cohn) G.W. Wilson, Mycologia 6 (2): 80 (1914) [MB453641]
Phytophthora paeoniae D.C. Cooper & Porter, Phytopathology 18: 881 (1928) [MB273265]


Type: SLOVAKIA, Bratislava, in the garden of Jacobi, Type Figures: Peronospora cactorum was first identified on cacti in 1870 by Lebert and Cohn. Habitat, intercellular in the parequima of various diseased rotten cacti. Observed in the host 1868/9.

Ex-type: LOST

Well-authenticated specimen selected by Gloria Abad:  CPHST BL 9 = P0714 (WPC) (Collection MUCL 9638)

Selected specimens in other collections

CPHST BL 9 (Abad) = P0714 (WPC) = CBS 231.30, ATCC200785, ATCC10091, Gallegly N93, MUCL 9638

Molecular identification

Voucher sequences for barcoding genes (ITS rDNA and COI) of selected specimens (see Molecular protocols page)

Phytophthora cactorum isolate CPHST BL 9 (= P0714 WPC) = ITS rDNA MG783385, COI MH136858

Additional sequences for molecular identification
ITS rDNA HQ261514 (isolate P0714), COI HQ261261 (isolate P0714)

Sequences for ex-epitype in other sources
Position in ITS phylogenetic tree

Clade 1a

Morphological identification

Colonies and cardinal temperatures

Colonies in V8 agar, potato dextrose agar, and malt extract agar with no distinct pattern. The minimum temperature for growth is 4°C, the optimum 24°C, and the maximum 30°C.

Asexual phase

Sporangia papillate, caducous with short pedicels (less than 4 μm in length), ellipsoidal, obpyriform, ovoid, or globose (24–50 L x 19–36 W μm) borne in simple or in close or lax sympodial sporangiophores. Hyphal swellings absent. Chlamydospores terminal and intercalary, globose (17–55 μm diam).

Sexual phase

Homothallic. Oogonia smooth-walled and usually hyaline (19–38 µm diam); antheridia paragynous, nearly spherical to club-shaped, and nearly always applied close to the oogonial stalk; oospores plerotic and aplerotic (20–26 µm diam), with an average wall thickness of 2 μm.

Most typical characters

Phytophthora cactorum is characterized by its production of caducous sporangia with short pedicels and paragynous antheridia.

Specimen(s) evaluated

Phytophthora cactorum CPHST BL 9 (Abad) = P0714 [World Phytophthora Collection (WPC) California, USA]

Hosts and distribution

Distribution: cosmopolitan
Substrate: leaves, stems, fruits, roots
Disease note: damping off of seedlings, fruit rot, leaf and stem rot, collar and crown rot, stem canker, root rot (Waterhouse & Waterston 1966)
Host: at least 154 genera of vascular plants in 54 families (Waterhouse & Waterston 1966)

Retrieved May 18, 2018 from U.S. National Fungus Collections Nomenclature Database.

Quarantine status

There is no quarantine for Phytophthora cactorum, as it is very prevalent and widely distributed around the world.

Additional references and links

Phytophthora cactorum in OSU Phytophthora Online course: Training for Nursery Growers. Oregon State University.

Fact sheet author

Z. Gloria Abad, Ph.D., USDA-APHIS-PPQ-S&T Beltsville Laboratory, United States of America