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Symptom Identification and Control Methods of Black Locust Mosaic Virus Disease

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[Distribution and Damage] Quite common in Beijing and Shandong. It affects the growth of young trees, causing dwarfism. [Symptoms] Irregular line patterns appear on the leaf surface, distributed without fixed positions, with beautiful patterns. Some leaves become smaller and lighter in color. If not carefully observed, it is easily overlooked. When adventitious buds in the leaf axils sprout, weak branches and small clustered branches and leaves are produced. In Eastern Europe, Central Europe or the United States, leaves become smaller, veins become transparent, petioles are short, plants are prone to cold damage, and there are often multiple branches and yellowing. The mosaic occurring in the United Kingdom appears mottled, with twisted leaves and curved wood.

[Distribution and Damage] Quite common in Beijing and Shandong. It affects the growth of young trees, causing dwarfism.

[Symptoms] Irregular line patterns appear on the leaf surface, distributed without fixed positions, with beautiful patterns. Some leaves become smaller and lighter in color. If not carefully observed, it is easily overlooked. When adventitious buds in the leaf axils sprout, weak branches and small clustered branches and leaves are produced. In Eastern Europe, Central Europe or the United States, leaves become smaller, veins become transparent, petioles are short, plants are prone to cold damage, and there are often multiple branches and yellowing.

The mosaic occurring in the United Kingdom appears mottled, with twisted leaves and curved wood. Diseased seedlings are dwarf, reaching only half the height of healthy plants. The hosts are black locust (Robinia pseudoacacia) and clammy locust (R. viscosa), with an incidence rate of about 10%.

[Pathogen] The virus particles of Robinia mosaic virus (RoMV) were first isolated in Hungary in 1961. Later it was also recorded in Yugoslavia, and it was considered to belong to Cucumber mosaic virus (CMV). The reported virus particle size is 40nm. When purified by special methods, the particles are circular, with a diameter of 27-28nm. It can be transmitted by aphids.

A report in China in 1981 stated that the virus particle diameter is 34nm. When inoculated onto Chenopodium amaranticolor, circular chlorotic halos appear on the seedling leaves; on cowpea seedlings, it shows systemic mosaic. The thermal inactivation point of the virus is 66-68°C, the longevity in vitro is 57 days, and the dilution end point is 10-4 to 10-5.

The virus can be mechanically inoculated. It is not transmitted through soil. Insects are the vectors. The cowpea aphid (Aphis craccivora) and green peach aphid (Myzus persicae) can carry the virus in a non-persistent manner.

This virus has a very wide host range, spanning more than 10 families. The natural infection symptoms in angiosperms are systemic mosaic and leaf distortion. Chenopodium amaranticolor, Chenopodium quinoa, common bean, tomato, etc. can serve as diagnostic hosts. Propagation hosts include Nicotiana glutinosa and common tobacco.

[Control Measures] Eliminating aphids can reduce the incidence of the disease.

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