The pathogen causing Dutch elm disease makes host trees attract insect vectors

Abstract

Dutch elm disease is caused by the fungal pathogen Ophiostoma novo-ulmi which is transmitted by the native elm bark beetle, Hylurgopinus rufipes . We have found that four semiochemicals (the monoterpene (−)-β-pinene and the sesquiterpenes (−)-α-cubebene, (+)-spiroaxa-5,7-diene and (+)-δ-cadinene) from diseased American elms, Ulmus americana , synergistically attract H. rufipes , and that sesquiterpene emission is upregulated in elm trees inoculated with O. novo-ulmi . The fungus thus manipulates host trees to enhance their apparency to foraging beetles, a strategy that increases the probability of transportation of the pathogen to new hosts.