Turnip mosaic virus; the abbreviation is TuMV.
Worldwide. Asia, Africa, North and South America, the Caribbean, Europe, Oceania. It is recorded from Australia, Fiji, French Polynesia, New Zealand, and Solomon Islands.
Many, especially brassicas, including broccoli, cabbage, cauliflower and radish. In Solomon Islands, Chinese cabbage is a host. The virus also infects lettuce and spinach, and some ornamentals, including zinnia and petunia.
A virus causes the disease. The term mosaic describes patterns of dark and light green on the leaves. These light and dark areas often occur either side of major veins (Photo 1).
Turnip mosaic virus is transmitted rapidly in a non-persistent way by several aphid species; this means that the virus does not multiply inside the aphid. As the aphids feed, the virus sticks to the needle-like mouthparts used to pierce and suck out plant sap from a leaf. When the aphid feeds on another leaf, the contaminated mouthparts transfer the virus. The virus is not transmitted in seed.
The transfer of sap from an infected plant to one that is healthy can also spread the virus, but the importance of this method compared to spread by aphids is not known. The absence of aphids on diseased plants is not an indication of their importance. Aphids often alight on a crop, feed and fly on to another plant if the first one is not to their liking.
Turnip mosaic virus is the most important and widespread virus disease affecting brassicas. The affected plants are not suitable for the market.
Look for leaves with distinct light and dark green patches.
Control of Turnip mosaic virus is difficult. The virus has a wide host range, insecticides do not prevent its spread, and there are several strains. Once the plants are infected with Turnip mosaic virus and show symptoms there is no way to make them healthy again, so it is important to prevent infection.
Resistant varieties of Chinese cabbage are available, but none are resistant to all of the several strains of Turnip mosaic virus that exist.
This is not an option. Insecticides take time to kill insects; by the time the aphids are dead, they have already fed and passed on the virus. Sprays of mineral oil (see Fact Sheet no. 56) may be useful to repel aphids.
AUTHORS Helen Tsatsia & Grahame Jackson
Produced with support from the Australian Centre for International Agricultural Research under project PC/2010/090: Strengthening integrated crop management research in the Pacific Islands in support of sustainable intensification of high-value crop production, implemented by the University of Queensland and the Secretariat of the Pacific Community.
This fact sheet is a part of the app Pacific Pests and Pathogens
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