MSU seeking hop samples for virus survey

Michigan growers asked to send plant samples to support a new hop virus research project underway at Michigan State University.

Hop stunt viroid.
Symptoms of Hop Stunt Viroid on hop. Photo by David Gent,

Carolyn Malmstrom, Michigan State University Department of Plant Biology, is seeking samples of hop plants that are currently, or have previously exhibited symptoms of virus. Submitted samples will be used for developing and optimizing a diagnostic system. A large and diverse set of samples is needed to optimize diagnostics. Because this is the development phase, initial assessments of virus/viroid diagnosis may be inconclusive.

Grower participation will be critical to the success of this project and help improve the diagnostic protocols with the ultimate goal of developing hop virus diagnostic tools to support effective diagnosis and clean plant initiatives essential for hop industry growth and sustainability.

Growers should sample plants that are actively, or have previously exhibited symptoms of virus. Growers are also encouraged to submit samples of plants that failing to thrive despite adequate management. Plants with an unknown issue may be infected with unknown viruses/viroids.


It is critical that protocol is followed exactly to ensure sample integrity. If you have any questions, email Malmstrom directly at

  1. Sample 10 hop plants per variety and yard.
  2. Wear latex/nitrile gloves during sampling and change gloves for each plant sampled to limit cross contamination.
  3. Collect leaf, stem and any underground root tissue of each plant that can be easily accessed and place it in a 1-gallon bag.
  4. Write the following information on the bag in permanent marker:
    • Contact name and number
    • Cultivar
    • Plant age
    • Date of collection
    • Sample number (1-10)
    • Any observations (stunted, leaf mottling, reduced yields etc.)
    • Location of sample (Identifying field name or location for future reference)
  5. The plant samples should be kept cool (cooler or fridge), but they should NOT be frozen.
  6. Samples should be shipped or dropped off on campus as soon as possible. Overnight shipping in a thermal bag/box with a cold pack is preferable.
  7. If a sample cannot be shipped fresh, the next best approach would be to let it air dry in the shade (not in the sun or in an oven) and shipped dry in a paper envelope (not plastic).
  8. Again, please email Malmstrom directly at with any questions.

This work is supported by Project GREEEN.

This material is based upon work supported by the USDA NIFA under Award No. 2017-700006-27175. Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the author and do not necessarily reflect the view of the US Department of Agriculture.

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