Incidence and impact of red leaf disease caused by Exobasidium vaccinii inlowbush blueberry fields in Nova Scotia

A survey of 54 commercial lowbush blueberry fields in Nova Scotia in 1998 s howed that the incidence of stems infected with red leaf disease, caused by Exobasidium vaccinii, had a median of 2.6%, a mean of 3.6%, and a maximum of 15.3%. Age, origin (from old pasture fields or woodlands), pruning histo ry (burn or mow) of the field and geographic region within the province wer e considered as covariates for explaining the differences in disease incide nce among fields. Age of the field was the only significant covariate with an average increase in disease incidence of 0.1% per year. Red leaf reduced the number of flowers by 42% and the number of berries per stem by 74%. Th e proportional loss in total yield in any field roughly equalled the diseas e incidence. The baseline data obtained in this survey will be useful for m onitoring incidence of this disease in the future.