Pest in focus: guava root-knot nematode

A new pest incursion has growers in the Bundaberg region on high alert.

Guava root-knot nematode (meloidogyne enterolobii) was detected in a backyard garden in Hervey Bay, just 100 kms away from Bundaberg, which produces 90% of Australia’s sweet potatoes and large quantities of chillies, ginger and watermelon, all proven favourites of the pest.

The first Australian detection of the pest was in the Northern Territory in September 2022, followed by a property in North Queensland in December 2022 and the most recent detection in Hervey Bay in February 2023.

Brisbane Markets wholesaler, Carter & Spencer Group, grows sweet potatoes and ginger in the region and is concerned by the potential impact on the industry.

According to the company’s Business Manager, Matthew Spencer, the current outbreak demonstrates how easily this microscopic, parasitic worm can be transferred across large distances in short periods of time.

“Guava root-knot nematode, if successful in spreading to key growing regions in QLD, would decimate many industries,” Mr Spencer said.

“At the frontline, an outbreak would greatly impact growers, their families and workforce, with a flow on effect to manufactures, logistics providers and retailers. A series of outbreaks would impact Australian consumers by creating supply shortages in lines impacted by the pest.”

Nematodes live in the soil and can damage the roots of plants, stopping them from taking up water and nutrients. They can be transmitted through contaminated soil and plant material, and once established are very difficult to remove.

“Guava root-knot nematode can be spread easily and there are many ways to move this pest across Australia, whether it be in soil, plant material or equipment movements, therefore on-farm biosecurity is key to limiting this spread,” Mr Spencer said.

“Industry and government has the duty of care to protect and preserve Australian food sources for current and future generations.

“Growers and growing regions would benefit from a wider campaign with public notifications of this pest, given the potential impact on our fresh fruit and vegetable supply.”

Click or scan the QR code for more information about guava root-knot nematode.

Symptoms of guava root-knot

Above ground, symptoms may resemble water and nutrient stress including stunted growth, wilting, and leaf yellowing. Underground symptoms include severe galling (knotty root growths stimulated by nematode infection) of the root system.

Guava root-knot nematode also directly infects edible below ground parts of the plant, like bulbs (e.g. onions), rhizomes (e.g. ginger), swollen roots (e.g. sweet potatoes), and tubers (e.g. potatoes). These can be severely deformed with large galls, a dark and cracked surface, and white round females can be found under the surface when cut open and examined with a microscope or hand lens.

Guava root-knot nematode is a significant threat to horticultural industries as it can be more destructive than other root-knot species and is able to attack crops that are resistant to other species of nematodes. The pest has been known to affect chilli, ginger, guava, onions, papaya, sweet potato, and watermelon, amongst other plants.