Carrot is an important vegetable crop in Australia, with some 330,000 tonnes produced annually from approximately 7500 ha, with a farmgate value of A$150M. Worldwide, plant-parasitic nematodes are recognised as an important constraint to carrot production.

Management of nematodes in carrots in Australia is heavily reliant upon the use of chemicals such as metham sodium and fenamiphos (Nemacur). Production of Nemacur in the USA is to cease in 2005. This, and the development of enhanced biodegradation in soils regularly treated with fenamiphos or metham sodium, suggests that alternative strategies will be required for nematode control in the future. A national project was conducted to determine the principal nematode species associated with carrot production in Australia and to develop improved methods of control.

Surveys and field trials in five states determined that the main nematode species associated with yield and quality defects were root knot nematode (Meloidogyne spp.) and lesion nematode (Pratylenchus spp.). Carrot cyst nematode (Heterodera carotae) was not detected in the survey, confirming the absence of this important pest in Australia. Changes were suggested to current sampling and extraction methods to improve the accuracy of pre-plant counts for soil nematodes. Break crops were identified that can be grown prior to carrot to reduce populations of particular species of nematodes.

Enhanced biodegradation of currently used nematicides was identified as an issue in carrot soils in some states. Alternative nematicides, including Telone and Telone C35 were trailed and found to be as effective as currently used nematicides. However, there are issues with environmental impact of nematicides, especially potential ground water contamination. An integrated approach to nematode control based on pre-plant nematode counts to identify the need for nematicide and the use of break crops prior to carrot production is advocated.

This project has been funded by Hort Innovation, using the research and development levies listed below and contributions from the Australian Government. Hort Innovation is the grower-owned, not-for-profit research and development corporation for Australian horticulture.

• Vegetable Fund