Experimental studies on factors influencing the transmission of Dutch elm disease

Abstract

Although various species of insects and arthropods have been considered as potential vectors of Dutch elm disease, there is little doubt that the current pandemic of the disease has been driven by the activities of just a few, highly effective bark beetle vectors mainly within the genus Scolytus. The disease transmission process, however, is highly complex. The behaviour of each beetle species, and even the behaviour of individual beetles, influences the transmission of Ophiostoma novo-ulmi and O. ulmi at many points in the disease cycle. Beetle behaviour during breeding in the bark of diseased trees affects the quantity and quality of pathogen spores carried by newly emerged beetle vectors. The behaviour of beetles during dissemination and host seeking affects how successful the transfer of the pathogen from vector to feeding groove will be and, ultimately, the potential for colonisation of a tree’s vascular system. The resistance mechanisms of elms themselves also play a part disease transmission including different resistance mechanisms operating in the feeding groove compared with the resistance mechanism in the vascular system. Experiments assessing the significance of these processes are presented in this paper.