CGMMV research update

CGMMV infects cucurbit plants and is responsible for significant economic losses worldwide. There are several strains of CGMMV worldwide and the primary avenue for spread is through contaminated seed.
Melons rarely show symptoms on the outside, however browning and lesions on the peduncle may indicate infection. When an infected fruit is cut open, the internal structure is sponge like with a meat texture. In this case, fruit is not suitable for sale.

In glasshouse trials and field surveys, a number of weeds and grasses have been identified as potential hosts of CGMMV. These plants do not show any physical symptoms, making it more difficult to determine if CGMMV is present. These include:

• Black nightshade
• Amaranth
• Pigweed
• Sabi Grass
• Wild Gooseberry
• Crowfoot Grass
• Caltrop.

Sorghum, the most widely used wet season cover crop in the Northern Territory (NT), is not a host and is safe to plant.

Two field trials were conducted in the NT to assess the role of bees in transmitting the virus. On each occasion, CGMMV was found on the flowers but not the leaves, suggesting that pollinators can introduce the virus into uninfected areas. CGMMV is typically found on the flower indicating transmission by bees/pollinators. All hive products (adult bees and brood, honey, pollen, empty cells, propolis) from the NT and Queensland trials have been shown to contain CGMMV. The pollen, honey and adult bees have the highest prevalence of the virus. The viability of CGMMV in hive products has been tested. So far, viable virus (capable of causing infection in plants) has been isolated from pollen, honey and adult bees. It is not currently known how long CGMMV remains viable inside bee hives. For information on good apiary management read the information sheet on our melon research page.

CGMMV can persist in the soil for at least 12 months, longer if infected plant debris is present. It is recommended infested areas are kept free of potential hosts (cucurbits and weeds) to ensure the lifecycle of the virus particles ends. This process can take more than 12 months. In the USA, it is recommended that infested soils are left to fallow for three years.
Now that the project is starting to wrap up, much of the information has been published on the internet. For more detailed information head on over to our melon research page.