Mosaic Virus diseases
Many viruses affect the cucurbit family. The important viruses include cucumber mosaic virus, watermelon mosaic virus and zucchini yellow mosaic virus. Field symptoms of these 3 diseases are similar and therefore it is very difficult to separate them by symptoms alone. Leaf symptoms include a prominent light and green mosaic pattern, mottling (yellow with green islands or blisters), and in severe cases, leaf distortion whereby affected leaves appear fern-like. Diseased fruits are malformed (slightly to severely misshaped with wart-like lumps).
Cucumber mosaic virus (CMV) It is not seed transmitted except through seed of perennial wild cucumber (Echinocytis lobata) and chickweed (Stellaria media). It is mechanically transmitted and in nature it is spread by various species of aphids (e.g. Aphis gossypii, Myzus persicae, etc.). The transmission mode by aphids is of the non-persistent type: the aphids acquire the virus from an infected plant and then transmit it to a healthy plant with their probing. They can acquire CMV from an infected plant in 10 to 30 seconds and can transmit the virus after feeding for as few as 9 seconds. It is also transmitted by striped cucumber beetles (Diabrotica vittata) and 12-spotted cucumber beetles (D. undecimpunctata) by mechanical means in plant sap carried on their mouthparts. It has a very extensive host range including such varied species as bananas, carrots, cowpeas, lupine, lilies, onions, passion fruit, potatoes and tomatoes.
Watermelon mosaic virus [Papaya ringspot virus-watermelon strain (PRSV-W), Watermelon mosaic virus 2 (WMV-2)] [p]This virus is mechanically transmitted and also spread by several species of aphids in non-persistent mode. It is not seed transmitted. Its host range is primarily restricted to cucurbits although one of its strains infects peas.
Zucchini yellow mosaic virus (ZYMV). ZYMV is transmitted from one plant to another by aphids (e.g. Aphis gossypii, Myzus persicae, etc.) in non-persistent mode and by mechanical inoculation. The virus is not seed-borne.
- Use tolerant or resistant varieties if available.
- Remove infected plants (disinfect hands and tools with 70% alcohol after contact with infected plants).
- Do proper weeding.
- Control insect vectors. A sustainable approach of controlling aphids is to prevent aphids reaching the crops and transmitting the virus.
- In case of squash mosaic virus use certified disease-free seeds.
