My forsythia bush has dead branches with hard knots, like nuts, on the stems. Is this a worm?
Forsythia Bush Infection
Certified GKH Gardening Expert
The fungus Phomopsis spp. causes growths, known as galls, to develop on the forsythia shrub, which can eventually weaken and kill branches. If you cut into the gall and do not see any hollow chambers or evidence of boring insects, then this is a good possibility of your problem. The best treatment is to prune out the galls (making cuts 3-4 inches below the gall) and dip your pruning tool in a 1:10 bleach/water solution between cuts so you don’t spread the disease. There is no cure for forsythia galls caused from the Phomopsis spp. fungus. All infected stems must be promptly pruned away and disposed of.