Association of Ophiostoma novo-ulmi with Scolytus schevyrewi (Scolytidae) in Colorado

Abstract

The smaller European elm bark beetle, Scolytus multistriatus, has been the primary vector of the Dutch elm disease fungus, Ophiostoma novo-ulmi, in elm trees in Colorado since 1948. An exotic from Asia, the banded elm bark beetle, Scolytus schevyrewi, was found in Siberian elm, Ulmus pumila, in Colorado in April of 2003; this was the first report of S. schevyrewi in North America. S. schevyrewi is now found throughout much of Colorado and in at least 21 other states. The similarities in breeding and feeding habits between S. schevyrewi and S. multistriatus have raised concerns about the ability of S. schevyrewi to serve as a vector for O. novo-ulmi. The objective of this preliminary study was to determine if O. novo-ulmi could be isolated from adult S. schevyrewi emerging from diseased elm trees. S. schevyrewi and S. multistriatus were allowed to infest diseased stem segments of American elm, Ulmus americana. The infested stem segments were caged and isolations were made from the adult brood that emerged. O. novo-ulmi was isolated from most of the adults of both beetle species, showing that S. schevyrewi could acquire the pathogen as effectively as S. multistriatus. Future studies are needed to determine if S. schevyrewi can effectively transmit the pathogen to healthy trees.

Semiochemical-Mediated Flight Strategies of Two Invasive Elm Bark Beetles: A Potential Factor in Competitive Displacement

“…Current information gathered on these two species is consistent with the occurrence of competitive displacement: (1) the observed relative abundances of the two species in the Þeld (Lee et al 2009); (2) both species co-colonize the same elm hosts in the Þeld (Negró n et al 2005, Lee et al 2006; (3) S. schevyrewi is a better competitor when larvae of both species are developing in the same host (Lee and Seybold 2010); and (4) S. schevyrewi seems to have a stronger kairomonal response to its host that elicits more rapid aggregation than does the pheromone produced in a delayed fashion by female S. multistriatus. The capability of high population densities of S. schevyrewi to kill drought-stressed trees (Negró n et al 2005) coupled with its capacity to vector Dutch elm disease (Jacobi et al 2007) suggest that this insect may threaten Ulmus trees that are relatively abundant shade trees in many urban landscapes of the United States (McPherson 1998;McPherson et al 2004).…”

“…S. schevyrewi was initially detected in 2003 in the United States (Negró n et al 2005) and is now known to occur in 28 U.S. states (Lee et al 2009) and in southern Alberta, Manitoba, Ontario, and Saskatchewan in Canada (CFIA 2007, Langor et al 2009). S. schevyrewi colonizes stressed elms (Shi and Chen 1990), causes tree mortality (Negró n et al 2005), and may vector one of the fungal species that causes Dutch elm disease, Ophiostoma novo-ulmi (Jacobi et al 2007). Despite their co-occurrence and the potential for confusion, the two bark beetle species are readily separated by external morphological characters, even by the nonspecialist (Negró n et al 2005).…”

Leptographium tereforme sp. nov. and other Ophiostomatales isolated from the root-feeding bark beetle Hylurgus ligniperda in California

“…However this beetle is not known to have a mycangium, and spores of Ophiostomatales on the exoskeleton of the beetle probably would survive in high numbers at low temperatures for a few days. Isolation frequencies of O. novo-ulmi Brasier from killed Scolytus schevyrewi Semenov that were shipped from Colorado to Iowa were just as high as from beetles that were plated immediately after killing (Jacobi et al 2007).…”

Dutch elm disease and elm bark beetles: a century of association

“…The few models describing the population dynamics of pathogen and insects consider climatic conditions only marginally. They are generally never focused on changing environments, nor on the prediction of future impacts in new areas or on new elm species, as recently observed in Colorado following the introduction of the banded elm bark beetle, S. schevyrewi Semenov from Siberia (Jacobi et al 2007). Studied carried out at larger geographic scale should hence lead to more dynamic models.…”