Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 13, 1997
Publication Date: N/A
Interpretive Summary: Wherever fruit flies occur or could be accidentally introduced, agricultural agencies must maintain a watch with traps to catch the adult flies. If flies are found either where they had not previously been found, or at population levels above a designated economic threshold, the agencies must spring into action to eradicate or suppress the outbreak or face a potential economic disaster to the fruit industries in the region. Trap lures employed for the purpose of detecting fruit flies are widely regarded as inadequate because they require bulky glass traps and are not as attractive as users would like. Needless to say, the more powerful the lure, the sooner the populations will be detected and the easier it will be to bring the situation under control. Recently, research in several laboratories around the world has shown that certain bacteria are extremely attractive to fruit flies and suggestions have been made that the chemicals sproduced by the bacteria would make powerful new attractants for trapping the adult flies. Here we report identification and evaluation of attractiveness of chemicals from cultures of two kinds of bacteria that are highly attractive to the Mexican fruit fly. A mixture of several of the chemicals was shown to be almost as attractive as the bacterial cultures themselves. Future plans are to test these chemicals in combination with other attractants to develop a new lure that is more attractive than existing ones and which can be used in traps that are both simpler and easier to handle than the current glass traps. If such a lure can be made, the result could be more powerful and less expensive fruit fly detection.
Technical Abstract: Headspace above tryptic soy broth culture filtrates of Klebsiella pneumoniae contained greater amounts of ammonia, methylamine, 3-methylbutanamine, 1-pyrroline, 2,3,4,5-tetrahydropyridine, and two pyrazines than were found above tryptic soy broth. It also contained chemicals not found above tryptic soy broth including dimethyldisulfide and dseveral alcohols and ketones. Headspace above tryptic soy broth culture filtrates of Citrobacter freundii contained greater amounts of ammonia, 1-pyrroline, and several pyrazines than were found above tryptic soy broth including dimethyldisulfide, some of the same alcohols as K. pneumoniae, a different ketone, and phenol. Additional chemicals were detected above filtrates that were saturated with sodium chloride or had their pH adjusted up or down. In laboratory bioassays with protein-starved, sugar-fed Mexican fruit flies, chemicals that did not contain protonizable nitrogen were not attractive. All chemicals containing protonizable nitrogen, except 2-methylpyrazine, were attractive. Synthetic mixtures of ammonia, trimethylamine, 1-pyrroline, 3-methylbutanamine, pyrazine, 2,3,4,5-tetrahydropyridine, 2,5-dimethylpyrazine and trimethylpyrazine in concentrations similar to those in filtrates of two bacteria were 73-87% as attractive as bacterial filtrates.