Association of Ophiostoma novo-ulmi with Scolytus schevyrewi
Scolytus schevyrewi (Coleoptera: Scolytidae – EPPO Alert List) is an exotic bark beetle from Asia which has recently been introduced into the USA. It was found for the first time in Colorado in 2003 on Ulmus pumila. It rapidly spread and by spring 2005, it was found in the following other US States: Arizona, California, Idaho, Illinois, Indiana, Kansas, Nebraska, Nevada, New Mexico, Maryland, Michigan, Minnesota, Montana, Oklahoma, Oregon, South Dakota, Utah and Wyoming. So far, it has not been reported from Canada or Mexico. The similarities in breeding and feeding habits between S. schevyrewi and S. multistriatus (the known vector of Ophiostoma novo-ulmi, Dutch elm disease) raised concerns about the ability of S. schevyrewi to serve as a vector for O. novo-ulmi. Preliminary studies were performed in the USA to determine whether O. novo-ulmi could be isolated from S. schevyrewi emerging from diseased elm trees. Stem sections of U. americana showing symptoms of Dutch elm disease (and then tested for the presence of O. novo-ulmi) were exposed to natural populations of elm bark beetles and placed in rearing cages. Isolations were then made from the adults that emerged. Results showed that S. schevyrewi could acquire O. novo-ulmi as affectively as S. multistriatus from diseased stem sections. O. novo-ulmi was recovered from S. schevyrewi in percentages comparable to that from S. multistriatus. Further studies are now needed to determine whether S. schevyrewi can transmit the pathogen to healthy trees.
Sources
Jacobi WR, Koski RD, Harrington TC, Witcosky JJ (2007) Asssociation of Ophiostoma novo-ulmi with Scolytus schevyrewi (Scolytidae) in Colorado. Plant Disease 91(3), 245-247.