​​​​Lauri A. Lutes and Jay W. Pscheidt

Dept. of Botany & Plant Pathology,
​Oregon State University, Corvallis, OR​


Dr. Martinez’s lab performed specific enzyme-linked immunosorbent assays (ELISA) for Tomato ringspot virus (Yellow bud mosaic/Eola rasp leaf diseases), Cherry rasp leaf virus (Rasp leaf disease), Cherry leafroll virus, and Prune dwarf virus (Virus-induced cherry decline; enations may be found when these viruses are found infecting the same tree). The results yielded the following:


Virus-Specific ELISA Result
(Symptomatic)		 Result
(Asymptom​​​atic)
Tomato ringspot virusPositiveNegative
Cherry rasp leaf virusNegativeNegative
Cherry leafroll virusNegativeNegative
Prune dwarf virusNegativeNegative


Now that Dr. Martinez has determined the causal agent of the symptom, she has to figure out how to best advise the grower, Bailey Williams, to manage their orchard.

GROUP ACTIVITY

Write an email to Bailey Williams explaining the finding and provide recommendations for managing this disease.


​WRAP-UP CASE QUESTIONS

  1. Did everyone in your group agree on a diagnosis? If not, did that impact the final disease management recommendations?

  2. What was the most challenging step in this process? Do you think this would be the most challenging step in real life?
    ​​
  3. ​ You have a limited budget to diagnose this sample. What is the most cost-effective way to diagnosis the sample to a point in which a reliable management recommendation can be made?

  4. What would you do if you were unable to confidently make a diagnosis?

  5. Some virus strains cause more severe symptoms than others. This means that a virus strain may produce symptoms that may not have a major impact on a grower, while other virus strains could be devastating. What would your recommendations be to the grower if you found a virus, but were unable to determine if it was a severe strain?

  6. The virus-like symptoms you observe on a sample do not match with symptoms of any of the diseases in the exhaustive list of resources you have used. How could you explain this? How would you proceed?
    ​
  7. Sometimes disease management recommendations can be devastating (e.g. orchard removal) to the grower, causing them to make decisions that may not be in the best interest of the community. If infectious trees are not removed, the virus can continue to spread to nearby orchards. How would you handle a situation in which a grower is refusing to remove virus-infected trees that are putting neighboring orchards at risk?

  8. Due to the cost of purchasing certified virus-free stock for propagation, some growers prefer to obtain propagation material from family or friends orchards. How would you make a case for investing in certified virus-free stock to someone that has used non-certified stock for years without a problem?

  9. Initial identification of viruses in an orchard is done largely by visual symptom recognition; however, symptoms may only be present during a short time period (e.g. Little cherry virus 2 symptoms (little, immature fruit that are not marketable) can only be seen about 10 days before harvest until fruit drop. Harvest is a busy time for growers, field representatives, and harvesters that have other priorities at this time of year. What disease management and identification recommendations would you make to growers, if this virus was suspected?

​Get the Answers to these Questions​