Root Infection of Woody Hosts with Verticillium albo-atrum

Abstract

Verticilium wilt is a plant disease caused by the fungus Verticil- Hum albo-atrum Reinke and Berthold. This pathogen is peculiar in tliat it does not confine its attacks to one host, or a few closely related hosts, as is so frequently the case with most other pathogenic fungi; it attacks a large number of widely unrelated plants, many of which are of economic importance. The disease does not often occur in forest stands, but it is becoming increasingly prevalent in plantings of ornamental trees and shrubs, particularly in temperate regions of the world. The present study initiated in 1970 and completed in 1972 deals with ( 1 the influence of root wounds and age of wounds on infection, (2) penetration and development of the fungus in susceptible and resistant woody hosts, (3) analysis of the growth response of young tree seedlings after root infection, (4) the influence of temperature and heat treating of soil on development of V. albo-atrum in excised roots, and (5) laboratory and greenhouse evaluation of fungicides against V. albo-atrum. This report is adapted from a thesis submitted to the University of Illinois in partial fulfillment of requirements for the degree of Doctor of Pliilosophy in Plant Pathology.