Fungi that invade apple, crab apple, hawthorn, and other plants in the rose family are referred to as scab and rust diseases. These fungi survive by invading the trees and taking nutrition from them, causing tissue damage and, in severe cases, death. While death of the tree is rare, the ornamental value of the tree is lost with the development of a scab and rust disease. Luckily, proper pest and disease control measures can help you achieve an acceptable level of mitigation.
When the fungi that cause scab and rust diseases start a new attack on a tree, they release their spores on cool, moist days. This usually begins in early spring when the tree starts to grow its new leaves. While cool, moist conditions prompt heavy infections, warm, dry conditions can reduce the extent of the fungi and their impact.
Once the fungi take hold and the infected leaves grow, rust spots or lesions will form on their surface. Eventually, these lesions will grow on the leaves, distorting them or causing them to curl. If the lesions are able to merge together, defoliation of the tree can occur and reduce any stored energy reserves.
At WillowStone, our solutions for scab and rust diseases involve applying plant protectant and other practices. For instance, properly pruning crab apple or hawthorn trees can thin their crowns and promote proper air circulation, creating an environment for the fungi that is less favourable. For additional information or to schedule a tree assessment, reach out to us today.