Virus Diseases

Blueberry virus diseases manifest in multiple ways depending on the virus involved: some cause leaf spotting with angular purplish-brown spots appearing about a month after bloom; others trigger premature fruit drop where berries develop to just 3-5mm then abort, leaving bushes virtually fruitless at harvest; still others cause leaf discoloration, mottling, or ringspots. Young leaves and flowers sometimes show transient red coloration absent in healthy plants. Some infected plants produce fruit normally but lack vigor and show reduced yields over time. In Western Washington's blueberry-growing regions, at least six different viruses circulate, with more emerging as surveys expand.

Multiple virus species infect blueberries here, including blueberry scorch, blueberry shock, and various ringspot viruses spread by different vectors including thrips, nematodes, and pollen. Once infected, plants are infected for life; no cure exists. Prevention is absolute: use only virus-tested and certified clean stock from reputable nurseries, and before planting, test soil for dagger nematodes and avoid fields with a history of viral disease. Remove and destroy any infected plants completely; simply removing symptomatic parts leaves the virus intact. If expanding plantings, don't set new plants adjacent to old, virus-infected fields where vectors can spread infection. Choose tolerant cultivars when available, and manage insect vectors during critical aphid flight periods (late April-May and September) using strategies from the PNW Insect Management Handbook.