What fungicide or chemical can treat black knot fungus on our dogwood tree?
How to Treat Black Knot Fungus on Dogwood Tree
Black knot infection typically occurs on trees in the cherry/plum genus, Prunus. Black stem disease affects dogwoods. Ugh! Read up on black stem disease and see if the symptoms match your dogwood. In either case, treatment consists in removing infected branches, cutting a good 6-8 inches back from the knot. Clean you pruning tool between cuts. Normally this is done in the dormant season before leaf break. Dogwood pruning cuts are susceptible to several diseases. By the time black knot is visible, it has been growing for at least a year. That means there are spores nearby ready to cause new infections this year. Using a fungicide rated for black knot and for dogwood prevents these lingering spores from starting a new knot. https://www.extension.umn.edu/garden/yard-garden/trees-shrubs/black-knot/