Guava root-knot nematode

Guava root-knot nematode (GRKN) is an aggressive, microscopic parasitic worm. Its scientific name is Meloidogyne enterolobii.

GRKN affects the following:

• horticultural and agricultural crops
• ornamental plants
• some weed species.

The pest is considered significant because of its:

• wide host range
• high reproduction rate
• severity of induced abnormal growths
• impact on yields in preferred hosts.

Where it is found

Guava root-knot nematode is found in tropical to subtropical areas of the world including:

• Central and South America
• Africa
• Asia
• several US states
• some European countries (in greenhouse settings).

Detection in the Top End

GRKN has been detected in the Northern Suburbs, Palmerston and other rural, remote areas.

It was found on the following host plants:

• sweet potato
• cucumber
• capsicum
• eggplant
• butternut pumpkin
• snake bean
• zucchini
• chilli plants.

The pest can also be found on:

• melon
• guava
• cotton
• tomato
• ginger
• cotton.

For more pests, read the simplified host document PDF (137.9 KB).

Appearance

At most life stages the GRKN is microscopic. This makes it extremely difficult to detect, especially:

• in soil or
• prior to symptom development in infected hosts plants.

Life cycle

GRKN is reliant on live roots to feed and reproduce.

Juveniles hatch from eggs in the soil or root debris, and travel through soil to invade new roots. They feed on roots and this stimulates cells causing root tissue to enlarge and form an abnormal growth.

Mature females lose their mobility and become sedentary. They can:

• produce eggs without males
• lay eggs either inside or on the root surface.

The eggs hatch immediately or can become dormant. Eggs can survive in the soil (without a host) for up to 12 months.

The pest takes about 4 - 5 weeks to complete its life cycle.

Females can produce 400 - 600 eggs in this time.

Damage

Typical symptoms of GRKN infection includes abnormal growths or knotting on roots caused by the pest feeding.

This affects the plants ability to uptake nutrients and leaves it susceptible to secondary pathogens.

Above ground your plant may display:

• stunted growth
• wilting
• yellowing of leaves.

This can often be mistaken for water or nutrient deficiency. It’s important to check your roots for signs of the pest.

Spread and dispersal

GRKN, like most root-knot nematodes can't move far on its own.

In the soil, their movement is limited to a few centimetres. Annually they may move a few metres.

How it's spread

The pest can be spread or introduced to new areas by:

• movement of infested plant material - host plants with roots
• soil - as is
• soil attached to equipment, machinery or plant parts
  • e.g corms, rhizomes, bulbs, or hosts and non-host plants with soil attached.

It can also be spread from property to property and on property through infested soil attached to footwear and tools.

It's important to maintain good biosecurity hygiene practices.

Irrigation water can also provide another dispersal mode on an infected property.

Prevention

To prevent spread of the pest you must:

• source planting materials from certified suppliers
• limit movements of soil
• follow good hygiene practices
  • e.g. washing soil from machinery and equipment prior to being brought onto the property, chemical footbaths etc.

Commercial growers should have an on-farm biosecurity plan to reduce the risk of introduction of plant pests and disease onto their property.

How to report

If you think you have seen guava root-knot nematode in the NT:

• call the exotic plant pest hotline on 1800 084 881 or
• contact the Plant Biosecurity team by:
  • calling 08 8999 2118
  • emailing plantbiosecurity@nt.gov.au.

How to submit a sample

To prepare your sample for sending, you must:

• print a sample submission form PDF (207.3 KB)
• follow instructions on factsheet PDF (939.3 KB).

Samples can be posted or delivered to Berrimah Farm.

You can also send a sample to be identified.

Post sample

Plant Pathology Section
Department of Industry, Tourism and Trade
GPO Box 3000
Darwin NT 0801

Deliver to

Berrimah Farm, BAL Building
Makagon Rd, Berrimah NT 0828

More information

For biosecurity alerts and updates, go to the Biosecurity NT Facebook page.

You can also call 08 8999 2188 or email plantbiosecurity@nt.gov.au.