Hylurgopinus rufipes, the native elm bark beetle (NEBB), is the major vector of Dutch elm disease (DED) in Manitoba. Dissections of American elms (Ulmus americana), in the same year as DED symptoms appeared in them, showed that NEBB constructed brood galleries in which a generation completed development, and adult NEBB carrying DED spores would probably leave the newly-symptomatic trees. Rapid removal of freshly diseased trees, completed by mid-August, will prevent spore-bearing NEBB emergence, and is recommended. The relationship between presence of NEBB in stained branch sections and the total number of NEEB per tree could be the basis for methods to prioritize trees for rapid removal.
Numbers and densities of overwintering NEBB in elm trees decreased with increasing height, with >70% of the population overwintering above ground doing so in the basal 15 cm. Substantial numbers of NEBB overwinter below the soil surface, and could be unaffected by basal spraying. Mark-recapture studies showed that frequency of spore bearing by overwintering beetles averaged 45% for the wild population and 2% for marked NEBB released from disease-free logs. Most NEBB overwintered close to their emergence site, but some traveled ≥4.8 km before wintering.
Studies comparing efficacy of insecticides showed that chlorpyrifos gave 100% control of overwintering NEBB for two years as did bifenthrin: however, permethrin and carbaryl provided transient efficacy. NEBB showed a gradual increase in development rate with increasing constant temperature. Lipid content of overwintering NEBB was higher in late fall than in mid-winter, which might show that depletion of fat reserves could jeopardize survival, but could be a result of conversion to cryoprotectants.
| Identifer | oai:union.ndltd.org:MANITOBA/oai:mspace.lib.umanitoba.ca:1993/23811 |
| Date | January 2011 |
| Creators | Oghiakhe, Sunday |
| Contributors | Holliday, Neil (Entomology), Westwood, Richard (Entomology) Hausner, Georg (Microbiology) Farenhorst, Annemieke (Soil Science) McIntosh, Rory (Entomology) Seybold, Steven Jon (Entomologist, University of California, Davis) |
| Publisher | Entomological Society of America |
| Source Sets | University of Manitoba Canada |
| Detected Language | English |
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