Scale insects on the underside of a noni leaf. These insects
are dead, having been colonized and killed by a parasitic fungus
(white, tufty mycelium of the fungus is visible at the peripheries
of the colonized insects, and is a natural biological control
mechanism).
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Noni stem, leaves and petioles infested with the green scale.
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Pest: Scale, the green scale (Coccus viridis). Scale insects are most often associated with and tended by one of several ant species.
Damage: Scales are sap-feeding insects that cause stunting and slow growth of noni plants and leaf curling and deformity if scale populations are large. They tend to feed along primary veins on the underside of noni leaves. The sugary waste product that is excreted from their abdomens provides a substrate for the growth of a saprophytic fungus that causes “sooty mold”. If ants and scales can be controlled, the sooty mold usually disappears after a short time.
Distribution: Scale insects are widely distributed throughout all of the major Hawaiian islands. Scale population outbreaks are favored at warm, dry locations or during warm, dry periods of the year.
Impact: Scales have the most negative impacts on the growth of noni seedlings in nurseries.
Control:
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- Biological control. In some environments, scales are controlled effectively by natural enemies and parasitic fungi.
- Spay applications of approved insecticidal soaps and oils.
- Ant control. If ants are controlled effectively, aphid populations generally decline.
- Hand removal and destruction of severely infested leaves and stems.
- Weed control or elimination of alternate hosts for scales.
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| Notes:
Scales were not previously reported as a pest of noni in Hawaii
or elsewhere in the world. Be advised that heavy use of insecticides
may eliminate populations of beneficial insects. |
