Insect Resistance of Elm Genotypes

Abstract

American elms (Ulmus americanaj were ravaged by the Dutch elm disease fungus beginning in the 1930s, leaving the future of the American elm uncertain. Extensive genetic improvement programs have historically focused on disease resistance, but more recently have included resistance to the elm leaf beetle (Pyrrhalta luteola), Japanese beetle (Popillia japonica), elm leafminer (Fenusa ulmi), spring cankerworm (Paleacrita vernata), and fall cankerworm (Alsophila pometari). Repeated defoliation by these insects can stress trees allowing for invasion by lethal wood-boring insects and pathogens and in some cases leading to tree mortality. By the 1990s nearly 20 new Asian elm species became available for study and hybridization programs. In general, Asian elms appear to have good levels of resistance to DED, leafminers, and elm yellows. In this chapter, I provide a comprehensive review of research findings focusing on preference and suitability of Asian, European, and North American elms for the elm leaf beetle, Japanese beetle, elm leafminer, and spring and fall cankerworms and the potential use of these elms in future elm breeding programs.