Melon Necrotic Spot Virus
(MNSV)
© The State of Victoria Department of Economic Development, Jobs, Transport and Resources 2015
This work is licensed under a Creative Commons Attribution 3.0 Australia licence. You are free to re-use the work under that licence, on the condition that you credit the State of Victoria as author. The licence does not apply to any images, photographs or branding, including the Victorian Coat of Arms, the Victorian Government logo and the Department of Economic Development, Jobs, Transport & Resources logo. To view a copy of this licence, visit
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If you would like to receive this publication in an alternative format, please telephone the DEDJTR Customer Service Centre on 136186, email via the National Relay Service on 133 677 This document is also available on the internet at
Disclaimer
This publication may be of assistance to you but the State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.
Melon Necrotic Spot Virus (MNSV)
What is Melon Necrotic Spot Virus (MNSV)?
MNSV is a plant virus that affects melon, watermelon and cucumber plants. It causes brown (necrotic) spots on leaves and stems and can also impact the quality of fruit and lead to reductions in yield.
Symptoms
Rockmelon
On rock melons the leaves may curl, wilt and have brown and light coloured spots (Figure 1). On the outside of the fruit, indentations and brown spots can appear (Figure 2), whilst the flesh maybecome dark, hollow and rotten (Figures 4 & 5).
Watermelon
In watermelons, small, transparent, yellow spots appear on the youngest leaves. As the plant matures, the spots turn brown and enlarge and the leaves curl, wilt and may die.
MNSV infected watermelon fruit often displays yellow or brown spots on the skins (Figure 3). The fruit may also be misshapen; with the flesh and rind becoming discoloured hollow or watery (Figure 6). In some cases, the fruit may decay while attached to the plant.
Symptoms can vary in severity and are often worse in cooler climates. MSVN can easily be confused with bacterial blotch of watermelon.
Spread
MNSV is widespread in horticultural production areas around the world.
Itcan be spread via infected seed, soil, water, irrigation water, mechanical damage (grafting and plant-to-plant contact) and the microscopic, fungus-like, root inhabiting Olpidium bornovanus (O. bornovanus).
The virus can survive in soil for several years. Once the plant is infected,MNSV persists for the life of the plant.
Figure 1.Leaf spots caused by MNSV (Photo Len Tesoriero, NSW DPI)
Figure 2. MNSV symptoms on the surface of rockmelon
Figure 3. MNSV symptoms on the skin of watermelon (Photo Len Tesoriero, NSW DPI)
Figure 4. Mild symptoms of MNSV on rockmelon
Figure 5. Severe (left) and very mild (right) symptoms
of MNSV on rockmelons
Figure 6. Necrotic spots and deformation in watermelon caused by MNSV (Photo Len Tesoriero, NSW DPI)
Management Options
To prevent MNSV or reduce its spread in your crop:
- Ensure staff and visitors adhere to on farm biosecurity and hygiene practices
- Use resistant varieties or graft onto resistant root stock
- Source seed, seedlings and graft material that is free of virus and from a reliable supplier
- Heat treat seeds for 144 hours at 70°C, which may kill the virus but still allow germination
- Test a proportion of seed and seedlings for MNSV
- Disinfect tools, propagating material and equipment with sodium hypochlorite (1% solution of a 12% concentrate of pool chlorine)
- Clean farm machinery, remove dirt and plant material with a high pressure hose, if possible spray machinery with 1% chlorine. Note chlorine will rust equipment and needs to be washed off after application
- Remove, feral, volunteer or wild cucurbit plants, which could otherwise act as reservoirs for the virus
- Remove infected plants and fruit from the crop
- Rotate crops out of cucurbits for three or more years to avoid carry-over of both the virus and O. bornovanus
- Consider soil fumigation
- Plan to work on younger plants before the older ones (the latter are more likely to be infected)
- Control insect pests, whichmay spread the virus
- Keep records of crop and paddock histories to enable pest and disease impacts to be monitored and traced
- Ensure the virus is not carried to areas free of the disease by runoff from rain or irrigation water.
Reporting and further information
Please report any suspect detections of MNSV to the Exotic Plant Pest Hotline on 1800 084 881 (toll-free) or email with photographs and a contact phone number.
For further information phone 136 186 for your local Plant Biosecurity Officer or email..
To arrange for virus testing, phone Crop Health Services on (03) 9032 7515.
© The State of Victoria Department of Economic Development, Jobs, Transport and Resources 2015This work is licensed under a Creative Commons Attribution 3.0 Australia licence. You are free to re-use the work under that licence, on the condition that you credit the State of Victoria as author. The licence does not apply to any images, photographs or branding, including the Victorian Coat of Arms, the Victorian Government logo and the Department of Economic Development, Jobs, Transport & Resources logo. To view a copy of this licence, visit
ISBN XXXXXXXXXXXXXXX / Accessibility
If you would like to receive this publication in an alternative format, please telephone the DEDJTR Customer Service Centre on 136186, email via the National Relay Service on 133 677 This document is also available on the internet at
Disclaimer
This publication may be of assistance to you but the State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.