The exotic plant pest Monosporascus cannonballus, commonly known as ‘Monosporascus root rot’ or ‘Monosporascus root rot and vine decline’, has been detected for the first time in Australia and has been confirmed at two locations in the Northern Territory. The root rot was detected in whole cucumber plants in the Darwin region, and in honeydew and rockmelon vines in the Katherine region. 

Monosporascus root rot is a disease-causing fungus that infects the roots of most cucurbits including cucumbers, pumpkins, squash, melons, and gourds.  Non-cucurbit plants can support the growth of the fungus without obvious symptoms of disease. This pest can have a high economic impact on watermelon and other melon crops. 

Most above ground signs do not appear until later in the season when within weeks of harvest older crown leaves begin to turn yellow and die and at this stage, symptoms advance rapidly. The disease appears to be limited to the root system with fruit and foliage not directly infected. The fungus spreads through contaminated soil and crop debris where spores can survive for many years in a dormant state without a host species present. 

Based on the evidence available, Monosporascus root rot is considered unlikely to be feasible to eradicate in Australia. Biosecurity authorities will continue to monitor the situation and manage the risks associated with this exotic plant pest. 

What you can do  

• Managing Monosporascus root rot revolves around integrated cultural practices, post-harvest sanitation, and chemical or biological intervention. 

• Inspect your crops regularly for presence of unhealthy plants or unusual symptoms. 

• Ensure that all visitors and staff adhere to on-farm biosecurity and hygiene practices.  

• Use clean propagation material, disinfect tools and equipment used on your farm and remove old plant material and fruit from your production area. 

• Report any suspected pest or disease to the Exotic Plant Pest Hotline on 1800 084 881. 

• Growers can also access the Plant Health Australia Monosporascus root rot fact sheet. 

• Biosecurity resources for growers are available on the farmbiosecurity.com.au website.  

• The AUSVEG Farm biosecurity manual is available to support the development and implementation of farm biosecurity plans, helping growers reduce the risk of introducing and spreading pests, diseases and plant pathogens.