Verticillium wilt of olive in Syria1

Verticillium wilt of olive was first recorded in Syria in mid‐1978 and confirmed as due to Verticillium dahliae. This article reports observations made in a comprehensive survey of the disease in nine provinces over 7 years. Percent infection varied from 0.85 to 4.5 in different provinces. Newly planted groves in lowland areas showed more infection than older groves in hilly areas. Isolation of V. dahliae was possible at all times of year. Young trees were more susceptible to wilt than older ones. The performance of 13 local cultivars against wilt was studied under natural field conditions and found to vary greatly from susceptible to resistant. Agricultural practices greatly affect spread of the disease. High disease incidence was observed in irrigated groves compared with non‐irrigated, and correlated positively with number of ploughings. Verticillium wilt causes a loss between 1 and 2.3% of total olive production annually.