新疆大白菜病毒病与甘蓝蚜的关系

甘藍蚜、桃蚜和棉蚜的有翅型与无翅型,均能传播大白菜病毒病,其中以甘藍蚜为最主要的传毒介体。一头带毒蚜可使80％的健苗发病;一头无毒蚜經吸毒一分钟的传病率为35％;健苗經一头有毒蚜传毒一分钟,就有10％发病。病毒系非持久性的,蚜虫一次吸毒后的传毒期限为25分钟左右。在烏魯木齐地区,有翅甘藍蚜全年中的迁飞高峯期,都是在7月下旬。証实了这时期与大白菜病毒病的流行,有极密切的关系。当年春、夏季播种的甘蓝和苤藍,尤其是晚甘蓝和晚苤蓝,是大白菜(包括冬蘿卜)苗期的初次毒源和蚜源。初步認为,能感染病毒的几种十字花科及藜科杂草,不是本病病毒和甘藍蚜的重要越夏寄主。

THE RELATION BETWEEN THE MOSAIC DISEASE OF CHINESE CABBAGE AND CABBAGE APHID IN SINKIANG

The mosaic disease of the Chinese cabbage (Brassica pekinensis Rupr.) has broken out in the vicinity of Urumchi. North Sinkiang, since 1955. In ordinary years it reduced more than 30 percent of the yield, while in an epiphytotic year such as 1961, the death rates of infected plants raised to 90-100% in the northern part of Sinkiang, and in other districts an average loss of 50 percent of the crop was not uncommon. The cabbage aphid[Brevicoryne brassicae (L.)], peach aphid[Myzus persicae (Sulz.)] and cotton aphid[Aphis gossypii (Glover)] are capable of transmitting the virus. The cabbage aphid is dominant in the cruciferous vegetable fields during the growing season and is regarded as the main insect vector of which the winged and wingless aphids have the same capability of transmission. One viruliferous cabbage aphid for each 2-leaved Chinese cabbage seedling results 80 percent of infection. One non-virulified aphid with a 1-minute-feeding on diseased plant is sufficient to acquire 35 percent of infection. On the other hand, one virulified aphid feeding on a 2-leaved healthy seedling for 1 minute results only 10 percent of infection. This virus belongs to the non-persistent group since 1 non-virulified aphid with a single feeding maintains its transmissibility only about 25 minutes. According to the field surveys made in 1960 to 1962 from June to October in Urumchi, the prevalence and severence of the disease depended, in a large extent, on the dispersion and population of the winged form of the principal aphid vector during the early seedling stage of the Chinese cabbage. In the past 3 years, the peak of flight of the winged form occurred about in the last part of July, and symptoms of the infected plants usually appeared in the middle part of August. It was therefore concluded that a great mass migration of the winged aphids is responsible for the epiphytotics of the disease. Field observation in the past years pointed out that the virus oversummered mainly in the cruciferous vegetables, including Gan-lan (Brassica olercea var. capitata L.) and Pie-lan (Brassica oleracea var. gongylodes L.). The naturally infected cruciferous and chenopodious weeds including Thlaspi arvense L., Cardaria pubesens Jarm., C. repens Jarm., Sisymbrium altissmum L., Chenopodium ficifolium Smith, and Chenopodium albaum L. seemed not to play as the oversummering hosts of the virus.