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Please note that as these reports may date back as far as the 1990s, the content and recommendations within them may be superseded by more recent research.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?

Foliage diseases and fungal rots were a major cause of crop losses in melons. Treatments available at the time did not provide sufficient protection under high disease pressure or during prolonged transport of fruit to market. Overuse of fungicides led to the development of resistance to control by many of the major pathogens. In addition, the domestic and international markets were placing pressure on farmers to reduce reliance on fungicides due to health and environmental concerns.

This project examined the efficacy of using a range of activators of natural plant defence to protect melons from fungal rots such as Fusarium, Rhizopus and Alternaria during the postharvest period. These chemicals not only helped maintain vine vigor and defence against common preharvest pathogens such as powdery and downy mildews, but we also showed that the preharvest sprays increased the shelf life of the melon, negating the need for postharvest fungicide dipping.

Preharvest applications of the defence elicitors BTH (Bion®, Syngenta Australia) ReZist® (Stoller Australia) and Silica as Silikamajic (Flairform WA), protected rockmelon fruit from postharvest disease significantly better than the control treatment. BTH provided a level of postharvest disease control at least as good as fungicide dipping for the major melons diseases. The plant defence elicitors did not adversely affect the quality of the melons in terms of yield, marketability, Brix°, flesh firmness, and colour and rind colour.

The outcomes of this research indicated that induced resistance could be used as part of postharvest disease control strategy. Ongoing research was focused on how induced resistance strategies could be incoroporated into integrated pest management programs, such as with generally regarded as safe (GRAS) chemicals to control postharvest disease for the melon industry.