Lettuce production is an important component of the Australian fresh vegetable industry, having in 1999 a gross value of $89.1M with export earnings of $6.7M over the same year. Nationally, two of the main market issues for Australian lettuce producers are: static fresh lettuce exports to south-east Asia, and crop losses due to microbial diseases such as Sclerotinia lettuce drop (SLD) and lettuce big vein (LBV).

SLD can be controlled to some extent, through the use of fungicides. The current project examined the use of fungicide alternative for SLD control. Potential use of a biological control agent was investigated, and soil amendment strategies (eg lime, compost) were compared with the use of registered chemicals to control SLD during crop production. This work parallelled research in Tasmania. These alternatives to fungicides were not promising in WA. However, the results from experiments conducted in Tasmania were quite different. The use of calcium hydroxide (with soil conditioning polymers) applied to the surface of the soil at a rate of 2.5 t/ha maintained the soil pH above 8.5 and resulted in a significant reduction (85%) in disease severity. Further experiments showed that an integrated approach using the calcium hydroxide treatment combined with strategies such as fungicides, rotation and drop irrigation offer an opportunity for enhanced and sustainable disease control of Sclerotinia minor in lettuce.

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