Blueberry samples should be taken from leaves that are symptomatic and young (3/4 expanded leaves). These ideal leaves are located towards the center of the blueberry bush. The best time to sample for blueberry viruses (BLMV, BlScV, BlShV, and BSSV) is early in the season (May to June) or late in the season (August to September). The best time to sample for nepoviruses (TRSV and ToRSV) is early in the season (May to June).
Sampling information provided by Dr. Robert Martin, Research Plant Pathologist for USDA-ARS in Corvallis, Oregon.