Root-knot nematodes in the NT
Guava root-knot nematode is found across a wide range of host plants in the Top End and Katherine regions. Farm hygiene is the key practice to prevent the spread of this pest.
The Department of Agriculture and Fisheries (DAF) is conducting Territory-wide surveys to determine the distribution, species composition, and crop impacts of root-knot nematodes across the Northern Territory. To date, three species of root-knot nematodes are well established in the NT and other parts of Australia. A fourth species, guava root-knot nematode (GRKN), has been detected more recently and is currently found in the Top End and Katherine regions.
GRKN infestations appear to be concentrated around residential suburbs of Darwin. When detected on commercial farms, GRKN is often associated with guava trees and vegetable crops planted in close proximity to infested guava. Although guava is a preferred host, GRKN has a very broad host range. This includes hay crops such as Cavalcade and rotational crops such as sunn hemp. GRKN can also infect many weed species, which may harbour nematodes between crop rotations and persist in inter-rows and fallows. These weed hosts can create isolated ‘islands’ of symptomatic plants within larger production blocks.
Good farm hygiene is essential to prevent the spread of GRKN and other root-knot nematodes. Boot washing and vehicle wheel washing are particularly important, and ‘come clean–go clean’ practices should be followed by farm staff and visitors moving between infested and clean areas. Sourcing clean planting material is equally critical, as the uncontrolled sharing of vegetative planting material, such as tubers, roots and soil, can spread root-knot nematodes.
Some commercial growers affected by GRKN have successfully reduced nematode populations through improved farm hygiene and the use of non-host rotational cover crops. Addition of high-quality compost and other organic amendments can also help suppress root-knot nematodes by supporting higher populations of natural enemies in the soil.
If you observe galled or knotted plant roots or would like further information about management, please contact the Plant Pathology team at plant.pathology@nt.gov.au.
