Progress 10/01/99 to 09/30/04
Outputs
The eastern larch beetle, Dendroctonus simplex LeConte (Coleoptera: Scolytidae), is a major pest of tamarack, Larix laricina (Du Roi) K. Koch, in Minnesota and in other boreal forest areas of North America. In 2001 and 2002, we investigated the chemical ecology of D. simplex in Minnesota. Semiochemical extracts of male and female D. simplex were prepared from three treatment groups of newly emerged insects [unfed, fed 48 hr on L. laricina phloem, or treated with juvenile hormone III (JHIII) in acetone]. Gas chromatographic-mass spectrometric (GC-MS) analyses of Porapak and abdominal extracts revealed that females produced frontalin (1,5-dimethyl-6,8-dioxabicyclo[3.2.1]octane), seudenol (3-methyl-2-cyclohexen-1-ol), and seudenone (3-methyl-2-cyclohexen-1-one=MCH). Feeding on phloem appeared to stimulate production of all compounds. Females and males treated with JHIII and injected with 14C-acetate resulted in the female-specific incorporation of 14C into frontalin. This
demonstrated de novo synthesis of frontalin by this species. Gas chromatographic-electroantennographic detection (GC-EAD) analyses demonstrated that both sexes responded to naturally occurring and synthetic frontalin, seudenol, and seudenone. Both sexes responded preferentially to S-(-)-frontalin and R-seudenol Field studies in three widely separated stands of L. laricina in Minnesota revealed that racemic seudenol was highly attractive in combination with the host monoterpene, (-)-alpha-pinene, but the addition of naturally occurring (-)-frontalin to this two-component mixture reduced the trap catch for both males and females. The reduction in trap catch due to frontalin was significant for females. Seudenone has not yet been tested in the field. Responses in this experiment were highly biased toward males (3:1), suggesting that a male-produced pheromone component may await discovery. Moribund L. laricina colonized by D. simplex are also colonized by many other subcortical insects,
and in our field studies we also trapped 8 spp. of Scolytidae, 5 spp. of Cleridae, 10 spp. of Cerambycidae, 5 spp. of Buprestidae, and 3 spp. of Siricidae. These studies revealed significant kairomonal responses by two species of checkered beetles (Thanasimus dubius and T. undatulus, Cleridae) and one species of roundheaded woodborer (Phymatodes dimidiatus, Cerambycidae) to the D. simplex pheromone components frontalin and seudenol, respectively.
Impacts
A better understanding of how chemicals are used by the eastern larch beetle and its predators (checkered beetles) will foster development of better sampling systems and enhance biological control possibilites.
Publications
- Seybold, S.J., Albers, M.A., and Katovich, S.A. 2002. Eastern larch beetle. USDA Forest Service, Forest Insect and Disease Leaflet 175, 12 pp.
- Hall, G.M., Tittiger, C., Andrews, G., Mastick, G., Kuenzli, M., Luo, X., Seybold, S.J., and Blomquist, G.J. 2002. Male pine engraver beetles, Ips pini, synthesize the monoterpenoid pheromone component ipsdienol de novo in anterior midgut tissue. Naturwissenschaften 89: 79-83.
- Hall, G.M., Tittiger, C.R., Blomquist, G.J., Andrews, G., Mastick, G., Barkawi, L.S., Bengoa, C.S., and Seybold, S.J. 2002. Male Jeffrey pine beetle, Dendroctonus jeffreyi, synthesizes the pheromone component frontalin in anterior midgut tissue. Insect Biochem. Molec. Biol. (In Press).
- Tittiger, C., Barkawi, L.S., Bengoa, C.S., Blomquist, G.J., and Seybold, S.J. 2003. Structure and juvenile hormone-mediated regulation of the HMG-CoA reductase gene from the Jeffrey pine beetle, Dendroctonus jeffreyi. Mol. Cell. Endocrinology (In Press).
- Seybold, S.J., and Tittiger, C. 2003. Biochemistry and molecular biology of de novo isoprenoid pheromone production in the Scolytidae. Ann. Rev. Entomol. 48: 425-453.
- Barkawi, L.S., Francke, W., Blomquist, G.J., and Seybold, S.J. 2003. Frontalin: De novo biosynthesis of an aggregation pheromone component by Dendroctonus spp. bark beetles (Coleoptera: Scolytidae). Insect Biochem. Mol. Biol. (In Press).
- Seybold, S.J., and Vanderwel, D. 2003. Biosynthesis and endocrine regulation of pheromone production in the Coleoptera, pp. xx-xx, in Blomquist, G.J., and Vogt, R., eds., "Insect Pheromones---Biochemistry and Molecular Biology," Academic Press, San Diego.
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Progress 01/01/01 to 12/31/01
Outputs
Since fall of 1999, we have conducted field trials to study the flight response of Colopterus truncatus (Rand.) and other nitidulid beetles implicated in the overland spread of oak wilt to the C. truncatus aggregation pheromone. Oak wilt is a vascular wilt disease that kills hundreds of thousands of red oaks in the United States each year, and is of great concern to forest managers and property owners alike. As a part of a larger study of the life history of these beetles, we used the C. truncatus aggregation pheromone to determine the seasonal flight period of C. truncatus and associated nitidulids. The pheromone is a 3 compound blend of methyl branched hydrocarbons isolated and identified by Cosse and Bartelt: (2E, 4E, 6E)-3,5-dimethyl-2,4,6-octatriene; (2E, 4E, 6E)-4,6-dimethyl-2,4,6-nonatriene; and (2E, 4E, 6E,8E)-3,5,7-trimethyl-2,4,6,8-decatetraene. We have monitored the flight of C. truncatus from early April until early November in 2000 and 2001 (ongoing)
using various combinations of whole wheat bread dough (WWBD) and male-produced C. truncatus aggregation pheromone as trap baits. The traps have been placed in four different sites ("blocks") around the Twin Cities area and have been emptied and re-randomized within the blocks weekly. Eleven different species of nitidulids were caught in the traps so far in 2001. As expected, C. truncatus was the most common beetle in the traps, followed by Glischrochilus quadrisignatus, which responded largely to WWBD. Results from 2001 have resembled results from 2000 in that there is a large peak of flight activity in late April and early May, trailing off to low levels in June. Of the treatments, the combination of pheromone and WWBD was the most attractive to C. truncatus during both years. We carried out an additional study testing for response of C. truncatus to oak volatiles and oak volatiles combined with C. truncatus pheromone. We used slightly modified traps to hold chipped oak tissue, and
placed them in four field sites. An experiment in 2000 showed that pheromone in the absence of WWBD is slightly attractive to C. truncatus. This year, we found that oak chips by themselves are not attractive to C. truncatus. Further, while C. truncatus did respond to the oak chips + pheromone treatment the response was quite low and likely due to the pheromone alone. Due to limitations in the amount of pheromone available, we were not able to include the pheromone alone treatment. We also performed an experiment testing for response of C. truncatus to two different blends of the C. truncatus pheromone, the naturally occurring 3-component pheromone and a 2-component pheromone blend (the octatriene and decatetraene). In the experiment both blends were combined with WWBD. We found that C. truncatus responded to both pheromone treatments at a higher rate than to WWBD alone, and that there was no significant difference between responses to either blend.
Impacts
This work has several implications for management of oak wilt. First, an effective pheromone-based monitoring system can provide important information on the activity period of oak wilt vectors. Land managers and forest health professionals can time pruning activities to avoid this activity period. Secondly, the use of the 2-component C. truncatus pheromone blend and bread dough provides a more cost effective monitoring tool. Finally, our results show that piles of chipped oak near uninfected trees will not likely attract oak wilt vectors.
Publications
- No publications reported this period
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Progress 01/01/00 to 12/31/00
Outputs
Since 1993 we have conducted research on pheromone biosynthesis in pine bark beetles (Coleoptera: Scolytidae) with an emphasis on de novo synthesis of ipsenol and ipsdienol by two model species, the California fivespined ips, Ips paraconfusus Lanier and the pine engraver, Ips pini (Say) 1. These and related species are pests of commercial, urban, and wildland pines in North America. These studies have been supported by extramural funding from the USDA NRI-CGP, from the NSF, from the USDA Forest Service, and recently from the University of Minnesota Graduate School. 2. Biosynthetic and regulatory studies are continuing on the late-stage reactions of the isoprenoid pathway in both I. pini and I. paraconfusus. The isoprenoid intermediate 3H-geranyl diaphosphate (GDP), was converted by whole body extracts of phloem-fed male I. pini from California and Wisconsin to 3H-myrcene. This provides the first unequivocal evidence for synthesis of a monoterpene in the Metazoa3.
Synthesis of myrcene by male I. pini appears to be stimulated by JHIII and feeding in a sex-specific manner, suggesting that it is related to pheromone biosynthesis. Furture studies are planned with I. pini and I. paraconfusus using both geranyl diphosphate and newly synthesized dydrozy-geraniol. Continuing projects on the chemical ecology of Coleoptera with other committee members of W-189 include field testing behaviorally active compounds for sap beetles (Nitidulidae) that vector oak wilt disease (with R. Bartelt, USDA Peoria) and the isolation and identification of pheromones from wood-destroying beetles in the families Anobiidae (with A. Coss, USDA Peoria). Ongoing work to characterize cuticular hydrocarbons and behaviorally active compounds of bark beetles (e.g. Ips perturbatus) continue with collaborators in the USDA Forest Service (M. Page, USDA-FS, Albany and E. Holsten, USDA-FS, Anchorage, see reference 4.
Impacts
Using the aggregation pheromone of Colopterus truncatus (Nitidulidae) has led to altered pruning guidelines for oak trees in order to reduce vectoring of oak wilt disease in the upper midwest. Potential use of sex pheromone of Ptilinus basalis (Anobiidae) for monitoring populations of this wood-destroying anobiid in structures. Wood-destroying anobiids are responsible for $10 million in pest control and wood-replacement costs annually in western North America. By studying pheromone biosynthesis in bark beetles, we are developing of new insecticidal targets based on the C10-specific isoprenoid synthesis of the pine bark beetles (Ips and Dendroctonus spp.).
Publications
- Seybold, S.J., Bohlmann, J., and Raffa, K.F. 2000. The biosynthesis of coniferophagous bark beetle pheromones and conifer isoprenoids: Evolutionary perspective and synthesis. Can. Ent. 132: 697-753.)
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Progress 10/01/99 to 12/31/99
Outputs
In research conducted or reported in 1999 and 2000 we have learned that the geographic ranges of three distinct mitochondrial DNA haplotype lineages of I.pini correspond to the geographic ranges of three pheromone races of I. pini(5. The enantiospecificity of the biosynthesis of the pheromone component ipsdienol differs in two of the three races where it has been studied (6). In the western or California race, the enantiomeric composition of ipsdienol produced by males fed on Jeffrey pine phloem [98%-(-)] is significantly different than that produced by males exposed to host myrcene vapors -[60%-(-)]. In the eastern race (Wisconsin), the enantiomeric composiiton of ipsdienol produced by males fed on red pine phloem [34%-(-)] is also significantly different than that produced by males exposed to myrcene vapors [26%-(-)], but the difference is less pronounced. The enantiomeric composition of ipsdienol isolated from males treated with juvenile hormone III (JHIII)
[western: 85%-(-); eastern: 42%-(-)] is significantly lower than ispdienol from fed beetles of the respective races. Ipsenol and amitinol, which are synthesized in 10 to 100 ng/male quantities by the western race, were not detected in extracts of the eastern race. In biosynthetic studies with the isoprenoid intermediate tritiated-geranyl diphosphate (GDP), we found that whole body extracts of phloem-fed male I. pini from California and Wisconsin both converted tritiated-GDP to tritiated-myrcene. This provides the first unequivocal evidence for synthesis of a monoterpene in the Metazoa (7).
Impacts
(N/A)
Publications
- Seybold, S.J., Quilici, D.R., Tillman, J.A., Vanderwel, D., Wood, D.L., and Blomquist, G.J. 1995. De novo biosynthesis of the aggregation pheromone components ipsenol and ipsdienol by the pine back beetles, Ips paraconfusus Lanier and Ips pini (Say) (Coleoptera: Scolytidae). Proc,. Nat. Acad. Sci. USA 92:8393-8397.
- Tittiger, C., Blomquist, G.J., Ivarsson, P., Borgeson, C.E., and Seybold, S.J. 1999. Juvenile hormone regulation of HMG-R gene expression in the bark beetle, Ips paraconfusus Lanier (Coleoptera: Scolytidae): Implications for male aggregation pheronome biosynthesis. Cell. Molec. Life Sci. 55:121-127.
- Tillman, J.A., Seybold, S.J., Jurenka, R.A., and Blomquist, G.J. 1999. Insect pheromones: An overview of biosynthesis and endocrine regulation. Insect Biochem. Molec. Biol. 29:481-514.
- Cognato, A.I., Seybold, S.J., and Sperling, F.A.H. 1999. Incomplete barriers to mitochondrial gene flow between pheromone races of the pine engraver, Ips pini (Say)(Coleoptera: Scolytidae). Proc. R. Soc. Lond. B. 266:1843-1850.
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