Dieback on forsythia
We were away from the months of February and March and when we came home I found my forsythia that had been in place for years with Dianne back on and not all ends but a good portion of the plant. I’m wondering if you can diagnose what this is. Was it just a cold snap after it started to bud?
Howard County Maryland
Hi - There are two possibilities for this type of wilting and dieback in forsythia.
White mold is a fungal disease caused by Sclerotinia sclerotiorum and is favored by cool, wet spring weather. Early symptoms include stem cankers followed by wilting. Splitting open the hollow stems will sometimes reveal a dark structure called a sclerotium inside (it looks like a black grain of rice). Another possibility is a canker disease, https://extension.umd.edu/hgic/topics/cankers-trees-and-shrubs
Management is the same in both cases. Prune out and remove infected stems and branches. Prune to improve air circulation within the plant canopy. Forsythia is a type of shrub that benefits from renewal pruning. After flowering is the ideal time to prune these plants. https://extension.umd.edu/hgic/topics/pruning