Arboriculture & Urban Forestry 34(2): March 2008 semiochemical perception but that marking did shorten the adult lifespan. They also found that 99% of the bark beetles emerging from fluorescent-powdered brood logs became self-marked and these marks would remain under dry conditions. Linton et al. (1987) applied fluorescent powder to the bases of pine brood trees and brood logs before mountain pine beetle, Dendroctonus ponderosae Hopkins, emergence. They found the emerging adults easily marked themselves in a similar fashion as those treated in vacuum dusters. Numerous studies, including Shore and McLean (1988), Salom and McLean (1991), Safranyik et al. (1992), Franklin and Grégoire (1999), Franklin et al. (2000), Dodds and Ross (2002), and Hansen and Bentz (2003), have also used fluorescent powder marking techniques to successfully track the movements of adult bark- and wood-boring beetles. In most studies, beetles were trapped with either passive or semio- chemical baited sticky traps (Dodds and Ross 2002; Hansen and Bentz 2003). There are no published studies examining the ef- fectiveness of fluorescent powders for marking Hylurgopinus rufipes. The objectives of this study were: 1) to determine wheth- er fluorescent powder would mark emerging native elm bark beetle adults; 2) to define patterns of capture of beetles marked by fluorescent powder; and 3) to determine the distance marked beetles dispersed after spring and summer emergence. MATERIALS AND METHODS Two areas with dense populations of American elm and native elm bark beetle were assessed over a 3-year period. The first location, approximately 4 ha (10 ac) of contiguous forest, was used in 1994 and 1995 and was situated along the Red River near Glenlea, Manitoba (49°5015N, 95°1012W). The second lo- cation, a farm approximately 255 ha (637.5 acres) with a large 44 ha (110 ac) contiguous forest and adjacent open fields, was used in 1996 and situated along the Assiniboine River near Rosedale, Manitoba (49°3022N, 99°3025W). Both sites, located in floodplain deciduous forests, were composed mainly of unevenly aged populations of American elm, ash (Fraxinus spp. [Olea- ceae]), Manitoba maple (Acer negundo [L.] [Aceraceae]), and Bur oak (Quercus macrocarpa [Michx.] [Fagaceae]). The study was divided into two separate adult mark and re- capture periods: spring emergence from overwintering sites at the base of healthy elms and summer emergence after brood development in trap logs. The fluorescent powder, Day-Glo Arc- Yellow (AX-16), purchased from A.R. Monteith (77) Ltd., To- ronto, was used in both adult dispersal periods. A dissection microscope and a UVS 12 short-wave fluorescent tube provided 117 magnification and illumination to identify powdered, marked native elm bark beetles caught on sticky traps and Tanglefoot bands. Preliminary laboratory investigation showed the powder could be easily detected on marked beetles. Spring Emergence Before adult emergence in late May, up to five mature elm trees each greater than 18 cm (7.2 in) diameter at breast height (dbh) and spaced 3 to 5 m (9.9 to 16.5 ft) apart were located in the center of the marking site. Each tree was coated with fluorescent powder on the bottom 1.3m(4.3 ft) of the trunk. After treatment, Scout or Delta passive sticky traps, purchased from Great Lakes IPM, Vestaburg, Michigan, U.S., were stapled at a height of 1.5 to 2.0 m (5 to 6.6 ft) on each powdered tree to capture marked beetles emerging from overwintering sites at the tree base. Sticky traps on powdered trees were collected and replaced with new ones on a weekly basis throughout the active flight period from May until late July. Each year, sticky traps were also placed on live elms at varying distances radiating from the center of the marking site in the four cardinal compass directions when possible (Table 1). The maximum trapping distance was in- creased in successive years (Table 1) after it was demonstrated that marked beetles could be collected at the maximum distance of the trial in the previous year. Actual trap distances from the center of the marking site were determined by the presence of elm trees. As a result of a lack of suitable trees, not all distances or directions were sampled equally each year. The experimental design and the scattered distribution of elm trees prevented a robust statistical assessment of beetle flight distance and direc- tion. Summer Emergence During early June each year, elm trap logs were placed in the stand to be colonized by native elm bark beetles. Trap logs were initially situated in an area of forest distant from the spring marking sites. All logs were approximately 1 m (3.3 ft) in length and 15 to 20 cm (6 to 8 in) in diameter. After colonization had occurred by the end of July, each trap log was transported and then thoroughly powdered, piled, and loosely covered by a wa- terproof tarp at the center of the marking site. After this, Scout or Delta passive sticky traps in 1994 and 1995, and Tanglefoot bands in 1996, were placed on live elm trees at varying distances in four cardinal compass directions. Like in the spring experi- ments, actual trap distances from the center of the release site were dictated by the presence of live elm trees and as a result of forest gaps, not all distances or directions were sampled equally. Table 1. Summary statistics for spring and summer marking experiments 1994 to 1996. Year Date of powder Spring experiments 1994 1995 1996 21 July 31 July 25 July 28 April 8 May 10 May Summer experiments 1994 1995 1996 Number of trap logs. dbh diameter at breast height. z ©2008 International Society of Arboriculture Total no. of powdered trees 4 3 5 28z 24z 68z Total no. of traps 24 31 37 12 24 28 Mean ± SEM tree dbh (cm) 22.2 ± 1.3 18.1 ± 0.9 34.2 ± 1.3 24.4 ± 1.6 19.3 ± 0.9 30.5 ± 2.3 30 50 1000 20 100 1000 Maximum distance of traps (m) Total no. of beetles collected Marked Unmarked 59 82 136 15 16 64 128 797 1491 283 911 20601
March 2008
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