Twig Blight

In blueberry fields and ornamental plantings across the Puget Sound, twig blight announces itself through wilting and red-flagged shoots appearing in summer, often accompanied by cankers at the base of infected canes. The fungus Diaporthe vaccinii produces tiny fruiting bodies embedded in the bark that ooze spores during wet weather, and when moisture is high, you may see silvery-looking tissue speckled with black dots around the infection site. The disease starts by infecting flowers during bloom and spreads down into shoots and twigs as the season progresses.

The reason twig blight has become increasingly important in British Columbia blueberry blocks (and poses risk in Western Washington) is its ability to infect through both flowers and wound sites, giving it multiple entry routes into your plants. If you grow blueberries, start with certified, disease-free planting stock and prune out infected branches at least 5 to 6 inches below visible symptoms, disinfecting tools between cuts. Some cultivars like Rubel show better resistance than susceptible varieties such as Duke and Legacy, so choose wisely when replanting. Most importantly, maintain good plant spacing and canopy management to keep foliage dry and promote air circulation, which reduces the wet conditions Diaporthe needs to thrive.