Pine beetle

The western pine beetle Dendroctonus brevicomis is perhaps the most destmctive insect enemy of western pine forests. The aggregation pheromone is a mixture of the terpenoid myrcene [123-35-3J (163) from the tree and the frass pheromones exo-hsevicomki [20290-99-7] (164) and frontalin [28401-39-0] (165). The Norway spmce beede Ips tppopraphus converts the tree terpenoid myrcene into the frass pheromone ipsdienol [33628-00-3] (166) and the beedes also produce 2-methyl-3-buten-2-ol [115-18-4] and rir-verbenol [473-67-6] (167), all of which are components of the aggregation pheromone. 

Recognising the acetal in frontalin (3), a pheromone of the western pine beetle," is not so easy. Nevertheless, it is Important to look for the two oxygen atoms joined to the same carbon atom ( in 3a) and disconnect the acetal before considering any other steps. 

Frontalin (18), the pheromone of the western pine beetle, is an acetal (atom has two single bonds to oxygen). Disconnection reveals diol ketone (19). 

Dioxalicyclo[3.2.1]octane, or (+)-exo-brevicomin (66), is the aggregating pheromone of the western pine beetle. It has been prepared from glucose using a procedure based on the retro synthesis design shown in Figure 1-2884 ... 

More recently, the deracemization of ( )-2c (Scheme 16) with Nocardia EHl and sulfuric acid in dioxane containing a trace amount of water (see above) afforded (S)-2-methyl-hept-6-ene-l,2-diol in 97% yield and 99% ee [83]. This intermediate was successfully applied in a short synthesis of (S)-(-)-frontalin, a central aggregation pheromone of pine beetles of the Dendroctonus family [81]. 

FIGURE 12 18 Relationship between degree of oxidant injury to ponderosa pines and bark-beetle attack (left) and numbers of trees killed by western pine beetle, mountain pine beetle, and the two species together (right). Reprinted with permission from Stark and Cobb. ... 

An enantioselective approach to both enantiomers of a-alkyl-a-methoxyarylacetic acid derivatives has been described from L-(- -)-tartaric acid. Key steps include stereoselective addition of Grignard reagents to 1,4-diketones derived from tartaric acid. This methodology has been applied in synthesizing the pine beetle pheromone frontalin. 

Recently, M. Asami and T. Mukaiyama 124) synthesized ot-benzyloxyaldehydes (109) having a chiral tertiary center at the ot-carbon atom in high enantiomeric excess by successive treatment of the aminal (102) with diisobutylaluminium hydride (DIBAL-H) and Grignard reagents. The asymmetric reaction is applied to the total synthesis of exo-(+)-brevicomin (110), the principal aggregation pheromone in the frass of the female western pine beetle (Dendroctonus brevicomis). 

Bicyelic endoperoxides. The novel bicyclic [3.2.1]endoperoxide 2 has been prepared in high yield by oxidation of the ketone 1 with 90% H202 in the presence of BF3 etherale. The mechanism of this oxidation is not clear. Benzo-phenone-sensitized ultraviolet irradiation converts 2 into the pine beetle pheromone frontnlin (3) in i)uanlitntive yield. In the absence of the sensitizer the epoxide 4 is... 

The syn alcohol 3, obtained from (R)-( - )-glutamic acid was used for an en-antiospecific synthesis of (+ )-exobrevicomin (4), the aggregation pheromone of the female Western pine beetle. 

R=OH). With less polar chloride substituents, however, the RhuA dia-stereoselectivity is reduced and a considerable fraction of the FucA configurated product (40%) is also formed. Interestingly, alkaline cyclization in the latter occurs with an inverse preference to furnish 177, which contains the enantiomeric bicyclic [3.2.1] structure shared by the FruA product 175 as well as by (S)-( — )-frontalin 178, the aggregation pheromone of the southern pine beetle Dendroctonus frontalis. 

Is of serious concern. The role of chemical communication, in relation to proposed control tactics, of predators and bark beetles will be discussed. Emphasis will be on Thanaslmus dublus (F.) (Coleoptera Clerldae) and Medetera blstrlata Parent (Dlptera Dollchopodldae) which are primary predators of the southern pine beetle, Dendroctonus frontalis Zimmermann (Coleoptera Scolytidae). 

It is the intent of this paper to explore the various control tactics that are being suggested in the management of bark beetles in the forest system with specific attention given to the potential impact on the predator population. Similar arguments could be extended to other bark beetle mortality agents such as the parasite community. Primary examples and control tactics discussed will be drawn from our experience with the southern pine beetle, I). frontalis, a major pest in the southeastern U.S., along with other bark beetles in North America. 

Cut and Leave. This method was first recommended by the Texas Forest Service for controlling small southern pine beetle spots (10-15 infested trees) that could not be salvaged (5). As the treatment implies, trees are felled with the tops directed into the infested area rather than random felling. Mortality to the bark beetles is enhanced by the increased subcortical temperature resulting from direct exposure of the bark to the sun s rays and the inability of the immature stages to move to more protected areas, i.e. the under-surface of the felled trees. 

It is interesting to note that in the registration process, information concerning the impact on these non-target species, such as the natural enemy community of bark beetles is not required. In both the remedial and preventive modes, the natural enemies are exposed to the insecticides. It has been shown (8) that overall emergence of predators was reduced by 89% and the ratio of natural enemies to the western pine beetle (D. brevicomis LeConte) emergence was reduced by 80% as a result of remedial use of 2% lindane on D. brevicomis. 

Pheromone Disruption and Inhibitors. Pheromones play an important role in the landing and attack behavior of bark beetles (9, 11, 12). Attractants orient flying beetles to a common host tree in high numbers over a relatively short time period. Two techniques have been recently developed to take advantage of the southern pine beetle response to pheromones. 

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... 

The second technique utilized frontalure which was placed as a bait on dead- or non-host trees in an attempt to suppress southern pine beetle spot growth (15). Since the technique employs chemical cues that the natural enemies utilize, i.e. kairomones in host location, it probably has little detrimental affect on the adult predators. However, the use of inhibitors and their impact on natural enemies is not known. The data base is lacking and we can only express concern. 

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