I live in S/W Mississauga (Clarkson). Last week I noticed the leaves on my Black Beauty Elderberry were turning black. I cut off all branches that were effected and sprayed it with Horticultural Oil Insect Spray. I’m not sure if the tree will be okay or not but now in the same area my columbine, milk weed and grape hyacinthus are infected, I have an apron o grass that in 3 days turned brown and the garden on the other side of that is being affected. I have Shasta Daisies there. The plants are a lime green and soft, the roots are black and look rotted. It seems to be something in the soil but I can’t find a bug. I took samples to Sheridan and their suggestion was to write and ask you.
I have gardened this area over 10 years. It is on a corner with well drained soil. Sun Shade Mix. I can’t beleive how fast this has happened. Because this blight is affecting mixed species I am at a total loss. Any suggestions would be appreciated.
Thank you for your inquiry. Your plants could be suffering from Verticillium wilt. Verticillium wilt is caused by two closely related soil borne fungi, Verticillium dahliae and V. albo-atrum. This disease infects a wide variety of trees, shrubs, vegetables and herbaceous plants including elder and Shasta daisy. Here is our answer to a similar question regarding this disease.
Unfortunately there is no easy cure for this disease once the plants are infected. Good cultural practices may keep the disease under control. For plants that exhibit mild symptoms, maintaining the plant’s vigor by watering during periods of drought and fertilizing may prolong the life of the plant. Mulching is also beneficial since it helps maintain soil moisture and moderate soil temperatures. Although infected plants cannot be cured, these practices can sometimes delay the progression of the disease. Verticillium fungi can survive for many years in the soil. Therefore, it is necessary to avoid planting susceptible species in areas that are known to be infected. In these cases, resistant or immune species should be planted.
Since fungal spores can be present in soil or debris, it is important to avoid moving soil or debris from areas of known infection. As a precaution against spread, all tools should be disinfested between cuts with a 10% solution of household bleach.
You may wish to have the soil tested to confirm this diagnosis. The City of Toronto’s Guide for Soil Testing in Urban Gardens, outlines a step-by-step process you can follow. Click here to view it.