Sustainable integrated control of foliar diseases in greenhouse vegetables (VG05094)

This is a final research report from Hort Innovation’s historical archives. Please note that as these reports may date back as far as the 1990s, the content and recommendations within them may be superseded by more recent research.

What was it all about?

Foliar diseases were a major problem in protected cropping and the industry requested investigations into sustainable disease management. A survey was conducted to determine growers’ understanding of foliar diseases, management strategies and how these could be improved. Growers wanted alternatives to fungicides and training in recognising diseases and selecting management strategies. Almost half of the growers thought it was getting harder to manage diseases and blamed an increase in disease pressure and increasing input costs. Growers highlight the difficulty in using fungicide resistance management strategies because of the limited number of registered fungicides with suitable withholding periods.

The two main diseases were powdery mildew, present throughout the year, and Botrytis grey mould which only developed in late autumn/winter. Regular disease and climate data was collected throughout the project and provided to growers to give growers a better understanding of the climate inside their greenhouses. The majority of growers producing in low technology unheated greenhouses were already doing all they could to manage the greenhouse climate. Greenhouses with heating were an advantage; however the use of heating had to be economically justified.

Potential new fungicides, alternative products and biologicals were screened for efficacy against the diseases, both alone and in spray programs. The most effective programs were those that used protectant fungicides early and systemic fungicides later in the crop or a regular program of alternative products commencing at the first sign of disease.

Although several fungicides showed potential these were not registered for use in protected cropping at the time. Agrochemical companies often did not support registration of products due lack of profitability and concerns with crop and human safety. Trials of alternative products were promising but additional data needed to be collected for registration.

None of the varieties evaluated were resistant to powdery mildew or Botrytis grey mould. Some were less susceptible and may have been useful when integrated with other management strategies.

Improved disease knowledge through factsheets, newsletters, grower workshops and information sessions had helped growers to make effective and responsible fungicide choices integrated with other strategies to ensure disease management was effective and sustainable.