Timely Viticulture Timeline: Pre-Bloom
May 01, 2020
By Dr. Joseph Fiola

Phomopsis

  • Phomopsis is the first disease on a grower's radar screen. 
     
  • Phomopsis cane lesions are common on spurs on cordons, therefore, as the buds from these spurs grow, the fungus can easily move from last year’s wood (spur) to this years new shoot and perpetuate the disease. 
     
  • If you had a significant infection last year or if you have a variety that is particularly sensitive or susceptible, early management is even more critical. 
     
  • If you have chronic problems with Phomopsis on spurs or you have a variety that is very susceptible at your site, you may benefit by switching to cane pruning to eliminate the cordons and spurs that are the reservoir for the fungus. 
     
  • Early control is the most important for controlling rachis infections, which is the most important source of economic injury.
     
  • Deadwood produces many more viable spores (perhaps 1,000s as many) than lesions on live wood. Cutting out dead wood can have a major impact on new infections. This is sometimes complicated as, typically, the most severely damaged wood is the bottom of last year's shoot, which is the section you want to keep as the new spur.
     
  • Phomopsis has a rain-splashed pattern of infection. Therefore, wood and canes below active lesions (on permanent or 2-year wood) usually get heavier infections than green tissue above the active lesions in permanent wood. This is especially critical in high cordon training and GDC as well as any of the vertically split canopies such as Smart/Dyson and Scott Henry.
     
  • This disease can also affect the fruit in the late-ripening season. Rachis (fruit stem) infections make clusters brittle and cause shelling of berries by harvest. For more detailed information please see Phomopsis Cane and Leaf Spot of Grape fact sheet HYG-3031-11 (pdf) from Daniel J. Anoco, Omer Erincik, and Michael A. Ellis, Department of Plant Pathology, Ohio State University Extension.

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