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Pests and Diseases
Noni Root Knot - click here for a new article by S. Nelson on noni root-knot disease

noni root knot
ABOVE: Stubby, swollen, galled noni roots after infection by root-knot nematodes (Meloidogyne sp.)


severe symptoms on roots

ABOVE: An older noni root with severe galling, distortion and cracking due to infection by root-knot nematodes.

ABOVE: Initial symptoms of root-knot nematode infection of noni: small galls.

noni root knot
ABOVE: Galled root system and cracked and girdled stem associated with severe root knot disease of noni.

dead tree

ABOVE: Noni tree killed by root-knot nematodes

girdled stem

ABOVE: Basal stem of noni plant is girdled due to effects of infection by root-knot nematodes (plant is dead)

noni root knot
ABOVE: Foliar chlorosis (yellowing), plant stunting, and root galling and necrosis associated with noni root knot disease.


nutrient deficiency

ABOVE: Yellowed noni leaves showing deficiency in nutrients (probably iron and other micronutrients) due to infection by root-knot nematodes.




Root-knot nematodes should be avoided at all costs

Disease: Noni root knot

Pathogen: Noni root knot disease is caused by a group of plant parasitic nematodes, Meloidogyne spp., known as the root-knot nematodes. These nematodes have wide host ranges and are able to infect many plant species. They can survive for long periods in Hawaii soils, even in the absence of host plants. The nematodes live in the soil and attack young noni roots. Their feeding and reproductive activities cause the noni roots to swell, develop galls and to crack open. After roots have cracked open, other opportunistic organisms (fungi, bacteria) can enter the noni roots and cause rotting.

Symptoms: Leaves are golden yellow; plants are stunted or unthrifty in appearance; root systems are stunted and sometimes rotten; roots galled, knotty, swollen, distorted, cracked and rotten; bark along base of stem may split open, leading to stem girdling by opportunistic fungi and bacteria; plant death is rare but can occur; low yields; sparse foliage.

Impact: Noni root knot can depress noni yields significantly. Replanting costs may be high in severe infestations and some fields may have to be abandoned.

Disease distribution: Noni root knot nematodes are distributed on all major Hawaiian islands, especially in older soils and ex-sugarcane lands.

Epidemiology: Disease often begins when seeds or cuttings are planted in nematode-infested soil. Nematodes are spread in contaminated soils, media, on tools and shoes and in water runoff.

  1. Avoid starting noni seedlings in untreated soils or media.
  2. Treat soils or media with heat prior to planting noni seeds (at least 120 degrees F for 15 minutes).
  3. Composts and chicken manure applied around the root zone helps to lower nematode populations.
  4. Use of foliar fertilizers in severe infestations will help plants to tolerate high nematode populations and severe infections.
  5. Avoid introducing nematode-infected plants to a new field.
  6. If plants are obtained from a nursery, inspect root systems for galling before purchase.
  7. Never purchase or plant a nematode-infected noni plant.
Notes: Noni root knot was previously unreported to occur in Hawaii and elsewhere in the world.

Last Updated on December 7, 2006