Structure elucidation of some insect pheromones : a contribution to the development of selective pest control agents

The use of pheromones is one of the methods currently being investigated intensively as an alternative method of insect control. The various ways in which pheromones might be used in insect control programmes are briefly discussed in Chapter 1.Chapter 2 gives a detailed description of the isolation and identification of the sex pheromone of the American cockroach, Periplaneta americana. The various techniques that have been used for the structure elucidation are described.The sex pheromone of P. americana contains two major components (periplanone-A and periplanone-B), as well as minute amounts of another four.Periplanone-B could be identified as (1 Z, 5 E)-1,10(14)-diepoxy- 4(15), 5-germacradiene-9-one. Periplanone-A proved to be very unstable, isomerizing to a biologically inactive compound. The instability of the compound rendered a complete structure elucidation impossible.The four minor compounds could not be collected in sufficient amounts to carry out a complete structure elucidation.Of the compounds reported to mimic the natural pheromone, only germacrene-D was found to do so. However, its threshold is very much higher than that of the natural pheromone. The same holds for the other reported mimics, even they do elicit electroantennogram responses. Regardless of concentration, none of the mimics elicit responses as marked as the natural pheromone.Apart from causing sexual excitation, periplanone-B also can attract males of P. americana.The isolation, identification and field evaluation of the sex pheromone of the leafroller moth, Archips podana, is described in Chapter 3. The pheromone consists of a mixture of equal amounts of cis -11-tetradecenyl acetate and trans -11-tetradecenyl acetate. Although the individual compounds are not attractive in field experiments, a 1:1 mixture of the two is capable of attracting many males of this species.Investigation of the sex pheromone of the false codling moth, Cryptophlebia leucotreta (Chapters 4 and 5) revealed that the pheromone is a mixture of equal amounts of cis -8-dodecenyl acetate and trans -8-dodecenyl acetate. This finding contradicts other reports which state that the pheromone of this insect is trans -7-dodecenyl acetate. Mixtures of cis -8- and trans -8-dodecenyl acetate in various ratios proved to be very attractive to males of this species.In Chapter 6 the isolation, identification and field evaluation of the sex pheromone of the potato tuberworm moth, Phthorimaea operculella, is described. The sex pheromone of this moth is a mixture of about equal amounts of trans -4, cis -7-tridecadienyl acetate and trans -4, cis -7, cis -10-tridecatrienyl acetate. These findings were confirmed by synthesis and by trapping experiments in the field