Integrated pest management of nematodes in sweetpotatoes (PW17001)

What was it all about?

From 2018 to 2023, this project extended knowledge on soil health and nematode management to the sweetpotato industry through masterclasses and other extension activities.

The research team conducted a range of fieldwork to develop new knowledge, including surveys to identify region-specific nematode species and issues facing the Australian sweetpotato industry; the investigation of management approaches including cover crops, soil amendments, tillage options and more; and the evaluation of new nematicide technologies.

Root-knot nematodes are widely distributed throughout the sweetpotato-growing areas of Queensland and northern NSW, and their feeding activity affects root initiation, stunting, skin damage and yield loss.

The research team studied agronomic aspects such as cover crops suitable for sweetpotato farming systems, management of difficult-to-kill volunteers and weeds and the use of organic amendments and reduced tillage practices in long-term farming system trials to improve soil health. Soil surveys demonstrated the diverse range of soils supporting sweetpotato production.

The project conducted the first comprehensive nematode species survey on sweetpotato-producing soils in Australia. Growers now better understand the plant parasitic nematodes causing yield loss and damage. The survey resulted in a new detection of reniform nematode outside of the known range, and a pest alert fact sheet was produced following the incursion of guava root-knot nematode into Australia.

Experiments provided new knowledge on the effects of two nematode species tested on two cultivars. The findings suggest that R. reniformis damage occurs at root formation, resulting in fewer roots. Infection with root-knot nematode (M. javanica) reduced roots' number and weight.

Sweetpotato growers now have increased awareness of weeds' nematode host potential and the importance of weed management. Trials gave growers new knowledge on herbicide efficacy for volunteer control and safe plant back periods. A review identified future chemistry options adaptable to Australian conditions. Growers provided learning on nematicide efficacy over the long winter cropping season.

The research identified thirty-six varieties of cover crops as resistant or highly resistant from the 103 screened. Out of 24 sweetpotato cultivars screened for resistance to two species of root-knot nematode, 15 were identified as resistant or highly resistant. Additional information on the host status of cover crops can be found on the Lucid key developed by this project.

Long-term trials indicated that high rates of organic amendments have the potential for effective root-knot nematode suppression and improved yield and long-term soil health benefits. Adding organic matter improved soil carbon and other desirable soil chemistry traits and supported an increase in beneficial soil organisms. Findings indicated a correlation trend between lower root-knot nematode and higher soil carbon.