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UBC Theses and Dissertations

Dispersal and flight behavior of Trypodendron Lineatum (Olivier) (Coleoptera: Scolytidae) as influenced by semiochemical and environmental factors Salom, Scott Michael


Laboratory bioassays using a wind tunnel were developed to study flight behavior and orientation of the striped ambrosia beetle, Trvpodendron lineatum (Olivier). Factors that were studied in detail were windspeed, semiochemical concentrations, and semiochemical combinations. In the first of two experiments examining the effect of wind speed on T. lineatum response to a semiochemical-baited substrate, the highest % of males (21.4) and females (25.3) caught in a funnel trap, occurred at 0.0 m/s. As windspeed was increased from 0.0 to 0.9 m/s, the percent of beetles caught decreased linearly for both sexes. A second experiment showed that in the presence of wind, responding beetles oriented anemotactically to the semiochemical-baited substrate. With wind absent, beetles flew randomly and erratically. Upon reaching close to the baited substrate, a greater proportion of the beetles responded to the chemical stimuli and landed on the substrate than when an airflow was present. These results suggest that T. lineatum are capable of responding under varied wind conditions typically present in a forest, whereby they use wind to orient to olfactory stimuli, yet are best arrested to the stimuli under still conditions. Flight response of T. lineatum to a multiple funnel trap baited with ethanol (1° attractant) and lineatin (2° attractant) at different release rates, indicated that only lineatin was effective in attracting beetles to this kind of trap. Maximum response by both males and females occurred at release rates of lineatin between 8 and 64 ug/24 h. However, in a more detailed study of T. lineatum response to ethanol and lineatin using modified drainpipe traps, serving as a model of a host tree, ethanol did positively influence male flight type, speed of reaction, and direction. Nevertheless, lineatin was the most important semiochemical in attracting males to land on and enter the traps. Ethanol was more important for females than for males, and when combined with lineatin, provided the optimal stimuli for attracting females to land on and enter the traps. Population movement of spring dispersing T. lineatum was studied using mark-recapture techniques with lineatin-baited funnel traps. In a first set of studies conducted in an even-aged second-growth coastal forest in British Columbia, beetle recapture distribution was compared with wind direction at distances between 5 and 500 m from the beetle release site. At 5 and 25 m, beetle recapture was predominantly upwind. With traps placed only at 100 m from the release site, beetles were recaptured in all directions irrespective of wind. However, with traps placed only 500 m from the release site, beetles were only recaptured in the downwind traps. In mark-recapture experiments conducted in a valley, beetles released from a forest margin influenced by prevailing up-valley winds, flew upwind within the forest to lineatin-baited funnel traps placed 25 m from the release site. Beetle recapture in an open setting was higher along the edge of the open setting than in its center, 325 m closer to the release site. Beetles were recaptured 1 km down-valley (upwind) and 1.9 km up-valley (downwind) from the release site. In one experiment (two releases), 10.6 and 7.8% of the marked beetles recaptured were collected in traplines ≥ 700 m and ≥ 1 km from the release site, respectively. In additional mark-recapture experiments in the valley, beetles were released simultaneously from a windward and leeward side of a forest margin in the valley through two experiments of four releases each. With long distance flight emphasized and no semiochemical-baited traps placed within 200 m of either release site, population movement was predominantly downwind. Beetles also flew across the valley to traps on the opposite facing slope at a fairly high frequency (38% of the recaptured beetles), during the first experiment. Beetles were recaptured at a much higher frequency in traps placed within a forest as compared to those in an open setting. This was likely a result of the calmer wind conditions under the forest canopy, facilitating better flying conditions and response to olfactory stimuli for the beetles. The implications these findings have on the general knowledge of scolytid beetle dispersal and orientation to olfactory stimuli are discussed. New considerations toward improving pest management strategies for T. lineatum as a result of these sets of studies are presented.

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