An Update on Verticillium Wilt of Australia

Pathologists from the NSW Department of Primary Industries have been surveying cotton diseases in all the cotton producing regions of NSW for 28 consecutive years. Quantitative data collected and stored in the disease survey database include the incidence and severity of Verticillium wilt and black root rot caused by the pathogens Verticillium dahliae and Thielaviopsis basicola respectively.  The increasing incidence of Verticillium wilt associated with the widespread adoption of reduced tillage practices prior to 1990 and the decreasing incidence of the disease following the release of cultivars with resistance to Verticillium wilt in 1990 was reported at the 1997 Beltwide Cotton Conferences.  Disease survey results since then show that the incidence of Verticillium wilt is increasing again in the Namoi Valley.  Survey results also show that the incidence of black root rot has increased dramatically since it was first observed in 1989.

The common occurrence of a high incidence of black root rot early in the season and a high incidence of Verticillium wilt at the end of the season suggests that there may be an interaction between the two pathogens.  The possible contribution of some tillage and irrigation practices is also discussed.