Pests and Diseases 
Noni anthracnose
Leaf spots scattered over noni leaf, with a large blighted area
due to coalescence of adjacent, expanding lesions.
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“Target spot” appearance of expanding lesions. Note
the diffuse, irregular margins of the mature lesions.
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Blighted leaf margins associated with noni anthracnose.
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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. |
| Control: |
- Sanitation (removal of severely diseased leaves for the
plant; removal and destruction of fallen infected leaves)
- Moisture and humidity management (ensure good drainage,
control weeds, adequate plant spacing, pruning, minimize
leaf wetness and overhead irrigation)
- Protective spray applications of approved fungicides.
- Avoid spreading the pathogen on hands and tools during
harvesting operations.
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| Notes: Noni anthracnose has not
been previously reported to occur in Hawaii or elsewhere in
the world. |
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