Cucumber green mottle mosaic virus

Symptoms

CGMMV symptoms vary with the type and cultivar of the host plant, environmental conditions, plant growth state at the time of infection and strain of virus.

Cucumber

• Green mottling occurs on young leaves and fruit surfaces.
• Whole plants may collapse.
• Even when leaves are asymptomatic, yield losses can occur.

Rockmelon (cantaloupe, muskmelon)

• Young leaves show mottling and mosaic patterns that often disappear from mature foliage.
• Fruit develops different degrees of malformation, mottling and disruption to surface netting.

Pumpkin, squash and zucchini

• Infected foliage can be asymptomatic or show leaf mottling and mosaic patterns.
• Fruit can have no external symptoms but still be internally discoloured and necrotic.

Watermelon

• Young leaves have mottling and mosaic patterning.
• General bleaching of foliage can occur.
• Leaf symptoms may fade in mature plants, and plants may appear to 'recover'.
• Brown necrotic lesions form on stems and fruit peduncles.
• Runners, or even whole plants, may die prematurely.
• Fruit can be misshapen with spongy, rotten flesh that can be yellow or show dirty red discolouration in the rind.

Seeds

Plant stage and plant parts affected

In general, younger plants show more severe symptoms; however, some host plants show no symptoms.

CGMMV is widespread in Asia, Europe, the Middle East, North America and Oceania, It is also present in Nigeria.

In Australia, CGMMV has been detected in New South Wales, the Northern Territory, Queensland, South Australia and Western Australia.

In Queensland, isolated detections of CGMMV have occurred in 2015 and 2017. The disease is confined to a few properties and there is a containment strategy in place to prevent further disease spread.

CGMMV infects commonly grown cucurbit crops and gourds. These include (in order of severity):

• watermelon (Citrullus lanatus)
• cucumber or gherkin (Cucumis sativus)
• rockmelon, also known as cantaloupe or muskmelon (Cucumis melo)
• honeydew melon (Cucumis melo)
• pumpkin (Cucurbita maxima or Cucurbita moschata)
• zucchini (Cucurbita pepo)
• bottle gourd (Lagenaria siceraria)
• snake gourd (Trichosanthes cucumerina)
• wax gourd (Benincasa hispida)
• bitter gourd (Momordica charantia)

Common weeds can also be infected. These include (in alphabetical order):

• amaranth (Amaranthus species)
• black nightshade (Solanum nigrum)
• common heliotrope (Heliotropium europaeum)
• fat hen (Chenopodium album)
• pig weed (Portulaca oleracea)
• some wild cucurbit plants, such as pie melon.

Once infected with CGMMV, a plant is diseased for life; there is no known cure. In crop host plants, CGMMV uses the plant’s replicating systems to reproduce itself and spread through all the plant's tissues (roots, stems, leaves, fruit, pollen and seed). The newly created virus particles are then transferred either in plant sap or through pollen or seed to new host plants to create the next infection.

CGMMV particles are very robust and can survive for long periods on hard surfaces (such as tools, equipment and vehicles), in soil and in water.

The role of weed host plants in CGMMV’s life cycle is not well understood.

CGMMV is a highly contagious plant virus that affects cucurbit crops such as cucumbers, melons and pumpkins. It causes:

• mottling, mosaic patterning and distortion of leaves
• mottling and malformation of fruit.

This leads to reduced marketability and yield loss.

Infection of these crops with CGMMV could significantly reduce Queensland’s crop production and value. In 2023–24 Australia produced:

• 262,298 tonnes of melons at a value of $284.9 million (38% of muskmelons and 32% of watermelons produced by Queensland)
• 106,628 tonnes of cucumbers at a value of $192.8 million (31% of this produced by Queensland)
• 119,665 tonnes of pumpkins at a value of $100.9 million (47.5% of this produced by Queensland).

Domestic restrictions have been implemented in outbreak areas to prevent spread of the disease. However, international market access can also be impacted, especially for seed and fresh produce exports, due to phytosanitary concerns.

Inspect crops regularly for plants with poor vigour, stunting or reduced yield. Check these plants for the presence of viral symptoms such as:

• leaf mottling and blistering
• vein clearing
• yellowing
• leaf deformation.

Fruit may not show symptoms on the outside, or may be spotted, streaked or distorted. Fruit can be discoloured or rotting inside.

If you suspect the presence of CCGMV or if you see symptoms that resemble CGMMV, report it immediately using 1 of these methods:

• Report online.
• Phone Biosecurity Queensland on 13 25 23.
• Phone the Exotic Plant Pest Hotline on 1800 084 881.

There is no cure for CGMMV; once infected, plants are infected for life. Therefore, the most effective means of control is prevention.

There are simple steps you can take to protect your farm:

• Source seeds from reputable suppliers and request a written statement verifying that the seeds (both cultivars and rootstock) have been tested and found to be free from the virus using the enzyme-linked immunosorbent assay (ELISA) method.
• Purchase healthy seedlings from reputable nurseries and check that they have been grown from ELISA-tested seed.
• Keep records of where you sourced plants/seeds and where they are planted on your property.
• Check new plants on arrival to make sure they are healthy, pest-free and disease-free.
• Regularly check your farm and report any unusual or unfamiliar symptoms.
• Maintain strict farm hygiene, always disinfect equipment and avoiding planting in contaminated soil.

Use these resources to help protect your farm from plant pests and diseases:

• Protecting your farm
• Biosecurity manual for the nursery production industry (PDF, 3.1MB)
• Biosecurity induction manual for Bundaberg horticultural farms (PDF, 1.3MB)
• Farm biosecurity.

CGMMV is restricted matter under the Biosecurity Act 2014.