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Pacific Pests & Pathogens - Full Size Fact Sheets

Cassava grey leaf spot (321)

Photo 1. Leaf spots, Periconia manihoticola, on cassava.

Photo 2. Leaf spots, Periconia manihoticola, on cassava.

Photo 3. Stalks bearing spores (at the top) of Periconia manihoticola, leaf spot of cassava.

Common Name

Casava grey leaf spot

Scientific Name

Periconia manihoticola; a previous name is Haplographium manihoticola.

Distribution

Wouldwide. Asia, Africa, South and Central America, Oceania. It is recorded from Fiji, Niue, Papua New Guinea, Solomon Islands, and Vanuatu.

Hosts

Cassava and rubber (Hevea brasiliensis).

Symptoms & Life Cycle

A fungus causing a leaf spot on cassava, somewhat similar to Passalora henningsii (see Fact Sheet no. 95), but affected areas usually larger, somewhat angular and more commonly resulting in withering and death of the leaves. The leaf spots are circular, up to 10 mm diameter, with pale centres and wide brown or purplish borders (Photos 1&2). On rubber, the fungus causes leaf spots and blight of the leaves, petioles (leaf stalks) and twigs.

Impact

A disease of minor importance on cassava, but there are reports of it causing leaf spots, blight of leaves, petioles and twigs, and premature leaf drop on rubber. This was reported from Brazil on seedlings of two clones in nurseries as well as plants in the field.

Detection & Inspection

Look for the small spots with pale centres and wide brown/purple margins. Look (using a hand lens or a low power microscope) for the erect stalk-like fungal structures on the spots with groups of spores at the tips (Photo 3).

Management

It is unlikely that disease management is necessary for grey leaf spot on cassava as there have been no reports of yield loss. However, on rubber the disease has been considered severe enough to warrant sprays of mancozeb or chlorothalonil every 7 days.

AUTHORS Grahame Jackson & Eric McKenzie
Photos 1&2 (taken by Eric McKenzie), and used in this fact sheet, appeared previously in McKenzie E (2013) Periconia manihoticola PaDIL - (http://www.padil.gov.au). Photo 3 Valmir Duarte, Universidade Federal do Rio Grande do Sul.

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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