Blueberry Scorch Virus
Blueberry scorch virus can cause severe flower and leaf browning in highbush blueberries. All varieties of highbush blueberry are considered susceptible. This disease is spread by aphids, with transmission from infected to uninfected plants taking place in a matter of minutes or hours. Aphid control is the best method available to stop the infection of the entire field. The virus spreads outward from the first plants infected.
The symptoms of blueberry scorch first appear during bloom in late April to early May. Symptoms in some varieties consist primarily of blossom blight with a few brown leaves near the blighted flower clusters and some marginal yellowing of leaves produced on older wood. The blighted blossoms often are retained throughout the summer but fail to develop into fruit. Affected bushes develop symptoms every year. Initially, only one or a few branches are affected. Bushes appear to recover as the season progresses; however, yield is reduced or eliminated. Symptoms reappear in following years with more branches affected. Plants can be killed in 3 to 6 years, with all plants eventually infected. Tolerant varieties may not show symptoms but still serve as sources of inoculum.
Blueberry scorch can spread rapidly. The best method of control is to plant virus-free stock. The spread of the virus has been recorded only over short distances. If no known blueberry scorch exists in close proximity to a grower's field, scorch should not become a problem. The problem occurs when a neighbor has tolerant varieties that are infected with this virus--these will be a constant source of potential new vector-spread infections. If an infection is observed early--when only a few plants are showing symptoms--then an aphid-control program combined with removing and burning diseased bushes over a 3-year period should prevent further spread of this virus. The Blueray, Bluetta, Duke, Chanticleer, Elliott, and Weymouth varieties are susceptible. Jersey is tolerant, and Bluecrop is intermediate.