Biosecurity officers found the invasive microscopic roundworm known as Guava Root-Knot Nematode in four Top End areas, the Department of Industry, Tourism and Trade said on Friday.

Test results from horticulture properties in Middle Point, Jingili, Palmerston and Malak suggest the parasite could have arrived in the Darwin area about a year ago.

Biosecurity staff have started working with infected properties and the agriculture sector to stop its spread, but it will be tough to eradicate.

The pest was found on sweet potato, cucumber, capsicum, butternut pumpkin, snake bean, zucchini and chilli plants.

Investigators have not found a link between the infected properties and testing continues to find out if the worm, that has a scientific name of Meloidogyne enterolobii, has contaminated other areas in the NT.

It spreads in soil attached to machinery, tools, footwear and plant products, and affects crop yield of several vegetables, fruit and agricultural fibres.

Infected plants can be identified by several symptoms including stunted growth, wilting, yellow leaves and deformation.

Guava Root-Knot Nematode was first described in 1983 from a population collected on Hainan Island in China, according to the Centre for Agriculture and Bioscience International.

It is found in tropical to subtropical areas across the globe, including Central and South America, Africa and Asia.

Australian Associated Press