My Japanese maple Sango Kaku succumbed to verticillium wilt, and I wanted a cornus kousa in the same spot. I see that “cornus” is listed as both susceptible and resistant, depending on the cultivar (and the strain of Verticillium present in the soil). I don’t know the strain of Verticillium, although I was informed by the arbourist who diagnosed the problem that he has seen a lot of it in our area in Japanese maples (Woodbridge-Kleinburg), and thought it had to do with a supplier.
I wondered if you might know which cultivars of cornus are resistant or immune, and which are susceptible…..
Many thanks for your help. (The site is sunny and moist, good loam but now the specific area is contaminated with the Verticillium, zone 5).
I am sorry for the loss of your Japanese maple to verticillium wilt. This fungal disease affects over 300 species of broad-leaved plants. There are two strains- Verticillium albo-atrum and Verticillium dahliae. According to the University of Guelph website, V. dahliae can live in the soil for many years whereas V. albo-atrum will survive only as long as it takes the crop refuse to break down (usually two years) unless other susceptible hosts are grown during this time.
Both the Missouri Botanical Garden and the University of Guelph’s Pest Diagnostic Clinic list Cornus (spp) as resistant or immune to verticillium wilt. Conversely, the Connecticut Agricultural Experiment Station lists Cornus as susceptible according to the cultivar and strain of fungus present in the soil. The most recent information was published from Guelph in 2012, so might I suggest you contact them directly for clarification? The contact information is E-mail: firstname.lastname@example.org and the website is: www.guelphlabservices.com
All the best!