Source Year: 2007

The incidence and severity of powdery mildew disease caused by Oidium heveae were assessed in forty clones of Hevea brasiliensis in different experiments in Assam, Meghalaya, Tripura and northern West Bengal. At the mature stage of growth, the severity of powdery mildew disease was evaluated for three consecutive years during the peak time of the disease (March-April) after wintering. Sixteen clones were found to be moderately tolerant with infection grades ranging from 1.5 to 2.5. Due to repeated massive premature defoliation caused by disease during March to May, die-back was noticed subsequently in clones PB 5/51, PB 235, RRII 300, RRII 51, RRII 105, RRII 5, RRII 430 and RRIC 105. These clones are therefore rated as highly susceptible to powdery mildew disease.