Bioassays, beetle pheromone

Brand, J. M., J. Schultz, S. J. Barras, L. J. Edson, T. L. Payne, and R. L. Hedden Bark beetle pheromones enhancement of Dendroctonus frontalis (Coleoptera Scolytidae) aggregation pheromone by yeast metabolites in laboratory bioassays. J. Chem. Ecol. 3,651—666 (1977). 

Use of automated headspace SPDE/GC-MS not only enabled the identification in female African elephant urine of a number of known insect pheromones (compounds 2-6, Fig. 2.1), but also revealed the presence of the beetle biochemical precursors to frontalin (2), exo-brevicomin (3) and ent/o-brevicomin (4), thus suggesting a common biosynthetic pathway (Goodwin et al. 2006). Extensive behavioral bioassays must be performed to determine whether any of these compounds is functioning as a pheromone among African elephants. 

The male-produced sex pheromone of the red flour beetle, Tribolium cas-taneum>has been identified to be (4 ,81 -4,8-dimethyldecanal 164 (tribolure) [320,321]. During bioassays, a mixture of the (4R,8R) and (4.R,8S)-stereoisomers proved to be more active than the pure (4 ,810-enantiomer [322]. The exact enantiomeric composition of the natural product remains as yet unknown. 4,8-Dimethyldecanal was found in other Tribolium species, too [323]. Factors affecting the pheromone production in T castaneum have been described by Hussain et al. [324]. 

Field bioassays with adult cerambycid beedes, Neoclytus acuminatus acumi-natus (F.) (Coleoptera Cerambycidae), revealed that males produce a pheromone that attracts both sexes. Male extracts revealed a single major male-specific compound IS, 3>S )-hexanediol. Field trials showed that a racemic blend of IS, 3S) and 2R, 3i )-hexanediols attracted both sexes and that activity was similar to enantiomerically enriched IS, 3S) hexanediol (e.e. 80.2%). However, a blend of all four stereoisomers attracted only a few beetles. ... 

Kuwahara, Y., Fukami, H., Ishii, S., Matsumura, F. and Burkholder, W. E. (1975b). Studies on the isolation and bioassay of the sex pheromone of the drugstore beetle, Stegobium paniceum (Coleoptera Anobiidae). Journal of Chemical Ecology 1 413 122. 

The first technique using pheromones to manipulate the southern pine beetle population relies on inhibition. Field bioassays have shown that aggregation of the southern pine beetle on attractant-baited traps can be significantly reduced by the... 

Table 17.1 Summary of published research on contact pheromones oflonghomed beetles and bioassays used to confirm activity.

Kuboki, M., Akutsu, K Sakai, A. and Chuman, T. (1985). Bioassay of the sex pheromone of the udo longicom beetle, Acalolepta luxuriosa Bates (Coleoptera Cerambycidae). Appl. Entomol. Zool., 20, 88-89. 

It has been discovered that the crucifer flea beetle, Phyllotreta cruciferae Goeze, a significant pest of oilseed Brassica and other cruciferous crops in North America and Europe, uses a hydrocarbon pheromone. The first published evidence for a pheromone in P. cruciferae was that canola plants infested by unsexed adults were more attractive to both males and females than damaged plants only, in both laboratory and field bioassays (Peng and Weiss, 1992). Subsequently, Peng et al. (1999) determined with field bioassays that the males were the attractive sex, fitting the pattern of a male-produced aggregation pheromone. 

There are other examples of volatile hydrocarbon pheromones in beetles that have been researched less extensively. One of these is from the broad-homed flour beetle, Gnatocerus cornutus (F.) (Coleoptera Tenebrionidae), a common stored-product pest. Tebayashi et al. (1998) found that males produce at least one compound that was attractive to both sexes in laboratory bioassays and at sub-nanogram levels. The compound was identified as the sesquiterpene (+)-acoradiene. The beetle-derived enantiomer was subsequently synthesized... 

Zilkowski, B. W., Bartelt, R.J., Cosse, A.A. and Petroski, R.J. (2006). Male-produced aggregation pheromone compounds from the eggplant flea beetle (Epitrix fuscula) identification, synthesis, and field bioassays. J. Chem. Ecol., 32, 2543-2558. 

However, whereas the silkworm female appears to attract males with a single sex pheromone, many other insects use blends of pheromones as chemical releasers of behavior. This phenomenon is strikingly illustrated in the case of males of the bark beetle Ips paraconfusus (=Ips confusus) which utilize three monoterpene alcohols as an aggregation pheromone (11). Maximum attraction of beetles in the field was exhibited in the presence of a mixture of all three compounds, whereas single or pairs of compounds were considerably less active (12). Similarly, in laboratory bioassays, mixtures of compounds were vastly superior to single constituents as attractants (13). 

The bioassay of (l/ ,55,7R)-(+)-exo-brevicomin (76) and its (-)-enantiomer 16 ) was carried out by Professor David L. Wood and coworkers at the University of California, Berkeley. When I visited his laboratory in June 1974, I was deeply impressed by the fact that only (+)-76 was pheromonally active to attract the beetles. A large-scale field test also indicated that (+)-76 was the bioactive isomer, while (—)-76 was neither active nor inhibitory.32 Thus, only a single enantiomer of the pheromone was found to... 

Frontalin (98, Figure 4.49) is the active component of the aggregation pheromone of the southern pine beetle (Dendroctonus frontalis), the western pine beetle (Dendroctonus brevicomis) and the Douglas-fir beetle (Dendroctonuspseudotsugae). Mori s 1975 synthesis of the enantiomers of frontalin via enantiomer separation (optical resolution) of an intermediate87 enabled their bioassay, and only (lS,5/ )-98 was bioactive as the pheromone component of D. brevicomis.32 A recent study on female D. frontalis revealed its (15, 5/C)-98 to be of about 91% ee.88... 

The existence of a male-produced aggregation pheromone in the nitidulid beetle, CarpophUus luguhris Murray, was demonstrated using a wind tunnel (flight) bioassay. 

Pheromone collections were also made as described for C. hemipterus (5). Tenax porous polymer was used to trap the volatiles emitted from groups of beetles feeding on pinto-bean diet. Parallel samples were derived from males, from females, and also from the diet medium alone, for later chromatographic and bioassay comparisons. Counts of beetles were kept so that the pheromone production could be quantified in terms of beetle-days. (A beetle-day is the average amount of pheromone collected from one beetle in one day). Beetles were separated by sex and set up for pheromone collection within a... 

Bartelt, R. j., P. F. Dowd, R. D. Plattner, and D. Weisleder, Aggregation pheromone of the driedfhiit beetle, Carpophilus hemipterus Wind-tunnel bioassay and identification of two novel tetraene hydrocarbons, J. Chem. Ecol., 16, 1015-1039 (1990). 

Four species of Trogoderma beetles use methyl-branched alkenals as their major sex pheromones 300). Aeration of T. gramrium and trapping of the volatiles on Porapak Q gave a 92 8 ratio of (Z)- to ( )-14-methyl-8-hexadecenal. The Z-isomer was the major component obtained from T. inclusum and T. variabile and the -isomer was obtained from T. glabrum. In laboratory bioassays males could discriminate between the geometric isomers. 

Gnathotrichus sulcatus produces 6-methyl-5-hepten-2-ol (sulcatol) (229) as its aggregating pheromone, as a 65 35 mixture of 5-(+) and R- —) enantiomers (31S). Borden et al. (316) found that this ambrosia beetle responded maximally to a racemic mixture (50 50) of the two enantiomers. In fact, the response to the racemic mixture was significantly greater than it was to a 65 35 ratio. More recent work, however, suggests that G. sulcatus responds to some extent to 5-(+)-sulcatol alone, that it does not respond to the 5 -(—)-isomer, and that the range of active ratios is much wider than previously indicated (317). In addition, Borden and coworkers (317) have found that G. retusus responds to (5)-(+)-sulcatol in an upwind laboratory bioassay and that the response appears to be inhibited to some extent by the S-(—)-enantiomer. They speculate that speciation may depend in part on the enantiomeric compositions of the pheromone. 

The response of the European elm bark beetle to isomers of its pheromone blend was determined with two separate laboratory bioassays and field tests (93, 318). A combination of 3 compounds that act syner-gistically was found (-)-4-methyl-3-heptanol (294a), (-)-a-multistriatin (303a), and (—)-a-cubebene (283) (for formulas, see pp. 48, 49) (93). The absolute configuration of the (—)-a-multistriatin is IS,2R,4S,5R (49) and that of the (—)-4-methyl-3-heptanolis 38,48(147). Both the texam alarm pheromone, (5)-(+)-methyl-3-heptanone, and the alcohol above share 45 stereochemistry. Of interest is the fact that the reduction of decalones by microbial enzymes is usually stereoselective, with optically active alcohols of 5-configurations being obtained (319). 

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