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2019 Virus Testing

Background

Maintaining healthy stock of every variety grown at Honken Dahlias has always been a top priority. We often dig just 75-80% of our dahlias and select only the most vigorous and healthy plants to sell and grow for the next year. Dahlias are often prone to lose their vigor, health or form over the course of many years due to genetic break-downs or viruses that infect plants. This is why you rarely see an “heirloom” dahlia. Most dahlias that are in circulation now have been only been bred in the last 10-15 years.

The American Dahlia society has recently offered some testing services for tuber vendors. With the cooperation of Dr Hanu Pappu at Washington State University (WSU) and the support of the Scheetz-Chuey Foundation, this service is offered to any dahlia grower that would like to investigate their stock. The goal of this service is to increase our knowledge of virus that impacts dahlias and to reduce the amount of virused stock in circulation.

Honken Dahlias Results

In 2019, Honken Dahlias sent in several samples to be tested by the University for testing. Each sample was tested for six different viruses - Dahlia Mosaic Virus, Dahlia Common Mosaic Virus, Cucumber Mosaic Virus, Impatiens Necrotic Spot Virus (INSV), Tomato spotted wilt virus (TSWV), and Tobacco streak virus (TSV).

Results indicated that all stock tested were negative for 5 of the 6 viruses tested. The only virus found in samples was Tobacco Streak Virus (TSV). Some researchers have observed this to be the virus that is least likely to show symptoms on infected plants. The varieties that tested positive for this virus that are in my catalog this season are

  • Ken’s Choice
  • Diva
  • Hollyhill Black Beauty
  • Miss Amara
  • Purple Joy

It is important to note that only 1-2 plants of each of these varieties were tested. **The tubers from the plants that tested positive were destroyed. I am still offering tubers from these varieties that are from plants that were NOT tested. The likelihood that they also carry TSV is unknown.

Other varieties that are offered in my catalog this season that tested negative for ALL viruses are:

  • Brookside Snowball
  • Clearview Peachy (two plants tested)
  • Cornel
  • Cornel Bronze
  • Hollyhill Black Widow
  • Isabel
  • Ivanetti
  • Lynn Slight
  • Tahoma Vivian

It is important to note that only 1-2 plants of these varieties were tested. Stock from tested plants will either be sold or grown again next year. The likelihood that other plants of these varieties are also negative is unknown.