116 Pines and Westwood: Mark-recapture Technique for Native Elm Bark Beetle Arboriculture & Urban Forestry 2008. 34(2):116–122. A Mark-recapture Technique for the Dutch Elm Disease Vector the Native Elm Bark Beetle, Hylurgopinus rufipes (Coleoptera: Scolytidae) Irene Pines and Richard Westwood Abstract. Six mark-recapture experiments were conducted in Manitoba, Canada, to determine the effectiveness of fluorescent powder to mark emerging native elm bark beetle adults, Hylurgopinus rufipes (Eichoff) (Coleoptera: Scolytidae), the vector of Dutch elm disease, Ophiostoma novo-ulmi (Brazier), after departure from overwintering sites in spring and emergence from broodwood in summer. Native elm bark beetles marked themselves on emergence from overwintering sites and summer trap logs. The spring and summer periods of flight activity for unmarked and marked beetles were similar. Marked beetles were captured over 1 month after peak emergence in the spring and 2 months after emergence from trap logs in the summer. Marked beetles were captured up to 1 km (0.6 mi) from release sites. Where integrated Dutch elm disease management activities are implemented in buffer zones to minimize the number of elm bark beetles entering community urban forests, buffer zones should be a minimum of 1 km (0.6 mi) in width. Key Words. Dutch elm disease; Hylurgopinus rufipes; IPM; marking; plant health care; Scolytidae. The native elm bark beetle, Hylurgopinus rufipes (Eichoff) (Co- leoptera: Scolytidae), is the main vector of Dutch elm disease, Ophiostoma novo-ulmi (Brazier), or variant strains in Manitoba (Brazier 1991; Westwood 1991). Beetles overwinter as adults at the base of healthy American elm [Ulmus americana L. (Ulma- ceae)] or Siberian elm [Ulmus pumila L. (Ulmaceae)] trees (Stro- bel and Lanier 1981; Anderson and Holliday 2003). In the spring, adult beetles emerge from overwintering sites and fly to the branches of healthy or recently stressed elms to feed. After feeding, they move into larger diameter branches or stems of dead or dying elm trees to construct brood galleries and lay eggs (Kaston 1939; Whitten 1964; Thompson and Matthysse 1972; Lanier 1982; Swedenborg et al. 1988; Pines and Westwood 1996). Adult native elm bark beetles sometimes feed on the main branches of living elms in the fall before overwintering (Gardiner 1981). Adults emerging from overwintering sites or summer broodwood may carry spores of O. novo-ulmi on their body and it is during their feeding activity that the inoculum can be introduced into the xylem of healthy elms (Gardiner 1981). McLeod et al. (2005) found that O. novo-ulmi metabolically manipulates an infected elm to increase production of four semiochemicals, thus enhancing the trees’ attractiveness to the native elm bark beetle and increasing inoculum dispersal. The distance a native elm bark beetle will fly to elm trees or elm brood material is not well documented. Kaston (1939) used elm trap logs in two elm-free areas and captured several native elm bark beetles up to 1.6 km (1 mi) from the nearest elms, but suggested the adults may have traveled farther. Kaston (1939) also indicated that emerging native elm bark beetles will not attempt to fly long distances if satisfactory elm material is nearby. Gardiner (1981) monitored an elm forest in Sault Ste. Marie, Ontario, Canada, and found that a population of native elm bark beetles remained sedentary in an elm stand for several years until the majority of elms perished from Dutch elm disease. ©2008 International Society of Arboriculture Subsequently, a mass migration of native elm bark beetles oc- curred in the late summer and fall, presumably when adults went in search of living elms in which to feed and overwinter. Ander- brant and Schlyter (1987) examined the dispersal behavior of two Dutch elm disease vectors in Sweden, the large elm bark beetle (Scolytus scolytus [F.]) and Scolytus laevis (Chap.). They reported that beetles seldom dispersed more than 50 m (165 ft) from infested elm stands over a period of several years. Birch et al. (1981) found that the smaller European elm bark beetle, Sco- lytus multistriatus (Marsh.), was able to fly 8 km (4.8 mi) from the nearest elm to baited sticky traps in remote communities in California, U.S. None of these studies actually used marked beetles; thus, it is impossible to determine the proportion of trapped beetles that originated from study sites or the actual distance beetles moved. The dispersal activity of the native elm bark beetle in North America in the spring and late summer feeding periods is poorly understood. In Manitoba, buffer zones (containing forested areas) of varying widths up to several kilo- meters wide around many towns and cities have been established and targeted for intensive integrated Dutch elm disease manage- ment activities to minimize the number of elm bark beetles en- tering community urban forests (Westwood 1991). Typically these activities include ground survey, sanitation, and trunk basal insecticide application. Currently there are no data available to guide forest managers implementing Dutch elm disease manage- ment programs regarding the optimum width of buffer zones or the distance beetles may move into protected urban forests. Many mark-recapture studies designed to track bark beetle dispersal have used fluorescent powders to mark adults (Linton et al. 1987; Shore and McLean 1988; Salom and McLean 1991; Cook and Hain 1992). Cook and Hain (1992) found that marking southern pine beetle, Dendroctonus frontalis (Zimm.), and southern pine engraver, Ips gradicollis (Eichh.), with fluorescent powders resulted in no adverse effects on flight initiation or
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