STUDIES ON LONGAN WITCHES’ BROOM DISEASE I.THE HISTORY OF THE DISEASE AND ITS SYMPTOMS,DISTRIBUTION AND DAMAGE

In Fujian, longan is an important fruit and its production is much higher than any other province in China. However, in recent years, longan has seriously suffered the witches’ broom disease.The disease showes various symptoms on different organs. The most typical symptoms are that young leaves on the infected shool become smaller and roll upwards, like a cresent moon; shoots develop with shortened internodes; overgrowing branches clump, like a broom; flower clusters appear because they are closely aggregated.During 1984~85, the investigation indicated that the disease had been widely spreading in 17 counties/cities in Fujian. In some regions, the disease has become severe and the yield of infected trees in 10~20% lower than healthy ones, and sometimes over 50% lower when the trees are infected seriously. The disease has been such an urgent problem that fruit growers request the authorities concerned to solve it as soon as possible.The disease is transmitting and spreading rapidly in Fujian since it is closely related with infected seedlings,its insect vectors and susceptibility of varieties. It is suggested that the plant quarantine be executed, disease-free seedlings be planted in the new orchard and the insect vectors be eliminated without delay.