Washington State University

Plant Pathology (subpage)

Plant Pathology in Hop, Year 1

Our objectives for the first year of the project were to

  1. Develop and evaluate the preliminary infection model for powdery mildew
  2. Determine susceptibility of hop cones to infection at different development stages
  3. Quantify crop losses due to powdery mildew when control measures are ceased at different developmental stages

We found that, while the critical cone susceptibility period is not precisely defined, it is an important factor in disease prediction and management. Infection models were developed. For more information on this component of our outreach, see the subpage on disease modeling.

We observed that the hop cones' susceptibility to disease appeared to decrease with cone maturity, although the bracts (as opposed to the bracteoles), did appear to retain some degree of susceptibility up to and following harvest. We also obseved a pattern of disease increase on cones that suggested the possibility of secondary disease spread between cones.

Our initial research determined several factors that can be managed to reduce risk, including the disease levels on the leaves of the plant, the timing of the fungicide applications, and the date of last fungicide application. In this initial year of research, controls applied through late July proved most impactful, while those applied later showed no significant effect on yield, aroma, bittering acids or storage index in most situations. When disease pressure was high, later applications were associated with higher yield and cone quality to some degree.

Click here to view a slide show including additional data and images pertaining to Year 1. (Large file, download may take several minutes.)

Click here to see information on Year 2.



Plant Pathology subpage

This page is designed to provide additional information pursuant to the Plant Pathology component of the overall project discussed on the Washington State University website http://hopmintstress.wsu.edu.

It is not designed to be viewed or utilized independently of that website.

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Various slides from Year 1 slide show

Slide show depicting Year 1 research efforts. (Large file, download may take several minutes.)

Washington State IPM Coordinator, WSU Irrigated Agriculture Research & Extension Center, Prosser WA 99350, 509-786-9287