As the acreage of hops continues to rapidly expand in the northeast, there is a great need for production knowledge specific to our region. Downy mildew has been identified as the primary pathogen plaguing our hop yards. This disease causes reduced yield, poor hop quality, and can cause the plant to die. Control measures that reduce disease infection and spread while minimizing the impact on the environment are desperately needed for the region. Mechanical control is one means to reduce downy mildew pressure in hop yards. Scratching is a practice initiated in the early spring when new growth has just emerged from the soil. The first shoots have an irregular growth rate and are not the most desirable for producing hop cones later in the season. Removal of this new growth through mechanical means helps to remove downy mildew inoculum that has overwintered in the crown. The top of the crown itself can be removed to further eliminate overwintering downy mildew. This practice is typically referred to as “Crowning”. While crowning is known to be effective in the Pacific Northwest, there is no established time frame for crowning in the Northeast. The goal of this project was to evaluate the impact of crowning/scratching at two different time periods on hop downy mildew pressure as well as hop yield and quality.


Vermont, University of Vermont

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