William D. Bedard
United States Department of Agriculture
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Featured researches published by William D. Bedard.
Science | 1969
William D. Bedard; Paul E. Tilden; David L. Wood; Robert M. Silverstein; Robert G. Brownlee
In the field, both sexes of the western pine beetle, Dendroctonus brevicomis, are attracted by the female-produced bicyclic ketal exo-brevicomin; this response is enhanced by myrcene (a constituent of the beetles host, ponderosapine), which is not an attractant by itself. This synergism may be part of the phenomenon of the mass attack on its host. Temnochila virescens chlorodia, one of the principal insectan predators of this beetle, is attracted by exo-brevicomin alone.
Journal of Chemical Ecology | 1980
William D. Bedard; David L. Wood; Paul E. Tilden; Q Kenneth LindahlJr.; Robert M. Silverstein
The responses of the western pine beetle (Dendroctonus brev-icomis LeConte) andTemnochila chlorodia (Mannerheim) to candidate attractants—exo- andendo-brevicomm, frontalin,trans-verbenol, ver-benone, and ponderosa pine turpentine and its major monoterpene components—were quantified by counts of beetles on traps baited with the various attractants, singly and in combinations released simultaneously. Combinations ofexo-brevicomin and frontalin plus a monoterpene or turpentine were the most attractive toD. brevicomis. The responses to these attractant combinations were reduced when verbenone plustrans-verbenol were present. All single compounds and binary mixtures, exceptexo-brevicomin plus frontalin, were much less attractive.exo-Brevicomin was most attractive toT. chlorodia, and this response appeared to decrease when verbenone plustrans-verbenol were present.
Journal of Chemical Ecology | 1980
William D. Bedard; Paul E. Tilden; Q Kenneth LindahlJr.; David L. Wood; Peter A. Rauch
Verbenone andtrans-verbenol were investigated as candidate interruptants for use as tree protectants. Verbenone andtrans-verbenol, pheromones released byDendroctonus brevicomis during host colonization, reduced the trap catch ofD. brevicomis near sources of the attractant composed ofexo-brevicomm, frontalin, and myrcene. Catch reduction at some trap positions was greater at a high release rate than at a low release rate oftrans-verbenol alone and of the combination of verbenone plustrans-verbenol. Verbenone also reduced catches at traps baited with attractive bolts from trees under attack byD. brevicomis. Attempts to use verbenone to protect living trees fromD. brevicomis attack were inconclusive.
Journal of Chemical Ecology | 1979
Lloyd E. Browne; David L. Wood; William D. Bedard; Robert M. Silverstein; Janet R. West
Three parameters are described for estimating the natural occurrence of chemically defined insect pheromones: (1) the rate and duration of release by the insect, (2) the density of the pheromone-emitting insect population in both time and space, and (3) dispersal and degradation rates of the chemicals. Each of these parameters, except dispersal, was estimated for a population ofDendroctonus brevicomis LeC, and its three component attractive pheromones. A single generation of 610,000 beetles, believed to comprise the entire population in a 65-km2 forest, was estimated to have released 0.78, 3.7, and 370.5 g of frontalin,exo-brevicomin, and myrcene, respectively, within a 30-day period.
Journal of Chemical Ecology | 1979
Paul E. Tilden; William D. Bedard; David L. Wood; Kenneth Q. Lindahl; P. A. Rauch
Western pine beetles were caught on unbaited sticky traps placed near a source ofexo-brevicomin, frontalin, and myrcene. Size of trap, distance and direction from the source of attractant, and height from the ground were varied. Significant differences in trap catch were observed in relation to each of the variables. Traps close to the source of attractant caught more beetles than traps farther from the source. Traps downwind of the source of attractant caught more beetles than did upwind traps. More males than females were trapped close to the source of attractant.
Journal of Chemical Ecology | 1983
Paul E. Tilden; William D. Bedard; Kenneth Q. Lindahl; David L. Wood
A sticky trap with 3 m2 surface area was modified by changes in attractant release rate, vertical dispersion of the attractant, and addition of a tree trunk silhouette to the trap axis. As attractant release rate increased, the number ofDendroctonus brevicomis caught at the source of attractant and at 1.5 and 5.2 m above ground on two vertical silhouettes 4.5 m away increased. In one experiment, more beetles were caught at a dispersed source of attractant than at a point source. Fewer beetles were caught at the lower traps on the two outlying silhouettes when a silhouette was at the source, than when no silhouette was at the source. As attractant release rate increased, the catch of a predator,Temnochila chlorodia, increased at the source.
Journal of Chemical Ecology | 1988
Paul E. Tilden; William D. Bedard
Abstractexo-Brevicomin (E), frontalin (F), and myrcene (M) were released at two rates 10-fold apart with verbenone at four rates 10-fold apart, and without verbenone in plots with one trap on a vertical cylinder at the pheromone source and one trap on each of four cylinders 5 m away. Catch of the western pine beetleDendroctonus brevicomis decreased with increasing levels of verbenone at both release rates of EFM, but not all differences in catch were statistically significant. Significantly more beetles were caught at the high rate of EFM than at the low rate, combining all rates of verbenone. The percent of total beetles caught at the center trap tended to decrease with increasing rates of verbenone, but the only statistically significant differences were at the low rate of EFM.
Journal of Chemical Ecology | 1980
C. J. DeMars; G. W. Slaughter; William D. Bedard; N. X. Norick; B. Roettgering
Sequential aerial photography was used to detect ponderosa pine trees killed by successive generations of the western pine beetle (WPB),Dendroctonus brevicomis Lec., over a three-year period during a study to evaluate the effectiveness of attractive pheromones for the suppression and survey of WPB. The total number of WPB-killed trees were estimated for each generation, using probability-proportional-to-size sampling procedures. Infested trees at the beginning of the suppression treatment totaled 283. Attacks by three successive WPB generations in 1970 killed 90,83, and 91 trees, respectively. The first generation in 1971 killed 47 trees and the two subsequent generations combined killed a total of 49 trees. During the suppression treatment, tree mortality was concentrated into the suppression plots in comparison to the check plots and the surrounding area. By 1972, tree mortality distribution returned to its original pattern, but at one-tenth the original level, as shown by maps. Recommendations suggest ways to improve the use of aerial photography for studies of WPB-caused tree mortality and population dynamics.
Journal of Chemical Ecology | 1981
Paul E. Tilden; William D. Bedard; David L. Wood; Harrison A. Stubbs
The catch of the western pine beetle,Dendroctonus brevicomis, at an attractive source of racemicexo-brevicomin, racemic frontalin, and myrcene was reduced by surrounding the source with a grid of 48 stations releasing all three compounds together, orexo-brevicomin alone or myrcene alone. Each compound was released at the rate of 2 mg/24 hr/station. The catch at an attractive bolt cut from a tree being colonized byD. brevicomis was not reduced byexo-brevicomin, but was reduced by the combination ofexo-brevicomin, frontalin, and myrcene in one of two tests. When a transect of traps was placed across a 0.81-hectare plot at six of the 48 stations releasing all three compounds, more beetles were caught at outer than at inner traps. More beetles were caught at unbaited traps on trees in a plot when the three compounds were released than when onlyexo-brevicomin or no compounds were released. A few trees were attacked byD. brevicomis in some of the plots. The antiattractant verbenone released from 48 stations at the rate of 4 mg/24 hr/station did not reduce the catch at an attractive tree bolt.
Journal of Chemical Ecology | 1985
Paul E. Tilden; William D. Bedard
Racemicezo-brevicomin, racemic frontalin, and myrcene were released at two proportions (5∶1∶400 and 1∶1∶1), each at three levels (1 ×, 10 ×, and 100 ×) in a ponderosa pine forest in central California. The 5∶1∶400 mix was based on an estimate of the relative amounts released from a ponderosa pine under attack by the western pine beetle,Dendroctonus brevicomis. MoreD. brevicomis were trapped at a source of the three compounds released at 5∶1∶400 than were trapped at a source released at 1∶1∶1, at all three levels, but this difference was statistically significant only at the 1 × and 10 × levels. Sex ratio of trapped beetles and distribution of catch at the source of attractant and 5 m away apparently did not differ between relative release rates.