12 - Wilt Diseases

Abstract

This chapter discusses wilt diseases. The diseases that affect the vascular system of a plant are called “wilt diseases.” Wilt diseases can kill a large and healthy tree during a single growing season. The attack on the vascular tissue by the fungus causes moisture stress that eventually leads to wilting. The vascular system performs the vital function of transport within the plant; therefore, the diseases of the vascular system can cause rapid killing of large branches and even entire trees. Wilt diseases can be separated into two major groups: those that begin in the branches as a result of leaf or bark feeding by pathogen-infested insects and those that begin in the roots as a result of wounding or direct root penetration by the fungus. Wilt disease fungi are facultative parasites that can live on the host after it has died. The dead host remains a source of inoculum for insect vectors or a center for the spread of soil pathogens for several years. Wilt fungi in the trunk and branches can be carried to new hosts by insect vectors. These fungi can also invade the healthy roots of the adjacent trees of the same species through root grafts.