Virus yellows in sugar beet – biology and infestation risk

Sugar beet became one of the most important sources for sugar production in the temperate zone. Sugar beet production is challenged by pests and diseases, restricting the genomic yield potential. With the intensification of the sugar beet cultivation, several of these pests and diseases became a major threat for the sugar production. The economically most important diseases are caused by viruses which are transmitted by soil organisms or leaf sucking insects like aphids or planthoppers. Virus Yellows disease which is caused by a complex of different virus species, is mainly transmitted by the aphid Myzus persicae and can lead to yield losses up to 50%. In Germany Beet yellows virus (BYV), Beet mild yellowing virus (BMYV) and Beet chlorosis virus (BChV) are economically most important, while Beet mosaic virus (BtMV) occurs only rarely. Beet western yellows virus (BWYV) is so far restricted to the US and Asia. Symptoms are highly variable and are characterized by chlorosis and necrosis as well as mosaic-like yellowing of older leaves. Infestation risk depends on natural fluctuation of the aphid population and is influenced by climatic conditions mainly in the winter months and infection time point during plant vegetation. The infection first occurs in patches before it spreads throughout the entire field. In the past, Virus Yellows has been efficiently controlled by neonicotinoid seed treatment. However, these substances have been banned in Germany since 2019. The widespread and frequent use of remaining insecticides will increase the selection pressure on the aphid populations leading to enhanced risk of insecticide resistance. Complete plant resistance against members of Virus Yellows has not been described yet; consequently resistant varieties are currently not commercially available. A durable control of Virus Yellows requires the development of alternative resistance strategies. Therefore, breeding for virus resistance remains the only control measurement. However, due to the changed conditions regarding the use of pesticides in sugar beet cultivation, breeding must be initiated promptly and with corresponding intensity.