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Blueberry (Vaccinium corymbosum) - Twig Blight
Cause This fungal disease, caused by Diaporthe vaccinii (formerly Phomopsis vaccinii), occasionally is in Pacific Northwest beds. This same fungus produces a disease of the fruit called viscid rot. Godronia cassandrae (asexual: Fusicoccum putrefaciens) has also been shown to be a causal agent, but at significantly less incidence than Diaporthe. Practices that encourage overly vigorous growth favor the disease. Current-year, spring growth is the most susceptible growth stage, although plants can be infected throughout the season if wounded. One study showed that stem-pierce wounds resulted in infection of more plants and typically greater tissue death than other wound techniques. Isolates from blueberry can also infect cranberry. Most cranberry cultivars appear to be susceptible to the disease.
Symptoms Leaves take on a yellowish cast early in spring and later become orange or bronze. Leaves often exhibit a yellow mottling before they turn completely yellow. Infected uprights generally die before bloom. Diseased and healthy uprights may be on the same runner. Vegetative and fruiting uprights are both affected. Roots are not affected. The disease may be in clusters or, more usually, scattered through the bed. As many as 25% of the uprights may be affected in certain beds.
Cultural control
- Do not over-fertilize.
- Provide adequate moisture and cooling during hot and dry weather.
- Limit foot and machinery traffic within beds to avoid wounds.
Chemical control Use shortly after budbreak.
- Quadris at 6 to 15.5 fl oz/A. Do not apply with silicone-based surfactants. May be applied on the day of harvest. Group 11 fungicide. 4-hr reentry.
For domestic markets only: Growers can use chlorothalonil products if their fruit is destined for DOMESTIC markets. Growers should check with their handlers before using any formulation using this active ingredient.
- Chlorothalonil products are registered. Do not apply within 50 days of harvest. Do not apply within 25 ft of marine/estuarine water bodies or release irrigation water from beds for 3 days after application. Apply only through solid-set sprinkler irrigation systems. Do not combine Bravo with surfactants or Dipel. Highly toxic to fish. Group M5 fungicide. 12-hr reentry.
- Bravo Weather Stik at 4 to 6.5 pints/A.
- Bravo Ultrex at 3.8 to 6 lb/A.
- Echo 720 at 4 to 7 pints/A.
- Echo 90 DF at 3.25 to 5.75 lb/A.
- Equus DF at 3.8 to 6 lb/A.
- Equus 720 SST at 4 to 6.5 pt/A.
Reference Catlin, N.J. 2005. Upright dieback disease of cranberry, Vaccinium macrocarpon Ait.: Causal agents and infection courts. Electronic Doctoral Dissertations for UMass Amherst. Paper AAI3193889. http://scholarworks.umass.edu/dissertations/AAI3193889