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Pests and Diseases
Noni anthracnose
Noni anthracnose
Leaf spots scattered over noni leaf, with a large blighted area due to coalescence of adjacent, expanding lesions.
Noni anthracnose
“Target spot” appearance of expanding lesions. Note the diffuse, irregular margins of the mature lesions.
Noni anthracnose
Blighted leaf margins associated with noni anthracnose.

Pathogen: Noni anthracnose is a leaf spot disease that is associated with an unidentified species of the plant pathogenic fungal genus, Colletotrichum.

Symptoms: Large expanding leaf spots with dark to tan centers and diffuse, irregular margins. Expansion of individual lesions results in their “target spot” appearance, i.e., concentric rings become visible in the lesions as the lesions grow each day. Lesions may coalesce to form large, blighted areas on leaves, often at leaf margins. Infected leaves may abscise (drop) prematurely. Symptoms are often most severe within dense noni canopies and/or on the lower leaves. Fruits and stems are not susceptible to infection.

Disease distribution: Noni anthracnose was first reported to occur in the Puna district on the island of Hawaii in 2001, and has since been observed in the Hilo/Panaewa area. This disease is likely to become established wherever noni is grown in areas that receive frequent or high rainfall.

Epidemiology: Noni anthracnose is favored by warm, wet weather and high relative humidity. The fungal spores are dispersed primarily by wind and splashing rain water.
  1. Sanitation (removal of severely diseased leaves for the plant; removal and destruction of fallen infected leaves)
  2. Moisture and humidity management (ensure good drainage, control weeds, adequate plant spacing, pruning, minimize leaf wetness and overhead irrigation)
  3. Protective spray applications of approved fungicides.
  4. Avoid spreading the pathogen on hands and tools during harvesting operations.
Notes: Noni anthracnose has not been previously reported to occur in Hawaii or elsewhere in the world.

Last Updated on December 7, 2006