David C. Robacker

Attraction of both sexes of Mexican fruit fly,Anastrepha ludens, to a mixture of ammonia, methylamine, and putrescine

Eight chemicals were evaluated in laboratory experiments as attractants for sugar-fed adult Mexican fruit flies. Ammonium bicarbonate, methylamine HCl, ethanolamine, pyrrolidine, putrescine, and monomethyl succinate were slightly attractive when tested singly. A mixture containing all eight chemicals was much more attractive than any of the individual chemicals. Through a series of experiments, a mixture of three of the chemicals was found that was at least as attractive as the original eight-component mixture. The final mixture consisted of ammonium bicarbonate, methylamine HCl, and putrescine in a 10∶10∶1 ratio. Ratios were less important than actual concentrations of individual components over the range of component concentrations tested. The three-component mixture was equally attractive to male and female flies over at least a 1000-fold range of concentrations and was slightly more attractive thanTorula yeast over the upper 10-fold range in competing McPhail traps in a greenhouse flight chamber.

Chemicals attractive to Mexican fruit fly from Klebsiella pneumoniae and Citrobacter freundii cultures sampled by solid-phase microextraction

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 several 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. It also contained chemicals not found above tryptic soy broth including dimethyldisulfide, some of the same alcohols as above K. pneumoniae filtrates, 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 the two bacteria were 73–87% as attractive as bacterial filtrates.

Attractants fromStaphylococcus aureus cultures for Mexican fruit fly,Anastrepha ludens

Volatile chemicals from tryptic soy broth cultures ofStaphylococcus aureus that attract sugar-fed, protein-hungry adult Mexican fruit flies were identified. Chemicals identified from the headspace above the filtrate of the bacterial cultures were ammonia, trimethylamine, isoamylamine, 2-methylbutylamine, 2,5-dimethylpyrazine, and acetic acid. Each chemical attracted flies. A mixture of the chemicals in the same concentrations as were found in the bacterial filtrate was 89% as effective in attracting flies as the bacterial filtrate in laboratory bioassays. Additional chemicals were identified from various concentrated or pH altered preparations made from the filtrate. Many of these chemicals also attracted flies. One of these chemicals, dimethylamine, was the most effective chemical identified. The use of solid-phase microextraction for volatile collection and of thick-film (5-µm) capillary GC columns was essential to the success of this work.

VOLATILES ATTRACTIVE TO THE MEXICAN FRUIT FLY (DIPTERA: TEPHRITIDAE) FROM ELEVEN BACTERIA TAXA

Filtrates of 11 bacteria representing 4 higher taxonomic categories were attractive to Mexican fruit flies, Anastrepha ludens (Loew) (Diptera: Tephritidae) in laboratory bioassays. All bacterial filtrates were more attractive at pH 9 than at pH 5 although filtrates at pH 5 were more attractive than water controls. The effects of pH on attractiveness of filtrates were consistent with an hypothesis that attractive principals of bacterial filtrates were various nitrogen-containing compounds and carboxylic acids that became more volatile at specific pHs resulting in increased attractiveness. Volatiles produced by the bacteria were sampled by solid-phase microextraction and identified by GC and GC-MS. Attractive principals identified were ammonia, aliphatic amines, pyrazines, imines, and acetic acid. Relative amounts of most of the chemicals were not closely tied to bacteria taxonomy.

A four-component attractant for the mexican fruit fly,Anastrepha ludens (Diptera: Tephritidae), from host fruit.

Sixteen chemicals found in fermented chapote fruit odor were evaluated as attractants for hungry adult Mexican fruit flies. Ethyl octanoate, ethyl benzoate, terpinyl acetate, ethyl salicylate, and (−)-α-copaene proved slightly attractive. Several of the chemicals also were tested for their ability to increase the attractiveness of the previously developed chapote-derived attractant (CEH) consisting of 1,8-cineole, ethyl hexanoate, and hexanol. Combinations containing CEH with ethyl octanoate, ethyl benzoate, 4-terpineol, (−)-α-cubebene, orα-terpineol were significantly more attractive than CEH alone. The two most attractive four-component combinations were ethyl octanoate with CEH (CEHO) and ethyl benzoate with CEH. No combinations containing greater numbers of chemicals were significantly more attractive than CEHO. Therefore, CEHO was selected for further study in this paper. Of CEHO component ratios that were tested, the most attractive was 10∶1∶1∶100 for the chemicals 1,8-cineole, ethyl hexanoate, hexanol, and ethyl octanoate, respectively. Formulations of CEHO into rubber septa and polyvinyl chloride (PVC) were aged 0–15 days and tested againstTorula yeast in competing McPhail traps in a flight chamber. Summed over all lure ages, rubber septa and PVC dispensers, respectively, were 1.2 and 1.5 times more attractive thanTorula yeast. PVC dispensers aged 10–15 days were approximately 2.1 times more attractive thanTorula yeast.

Research Reports: Laboratory and Field Olfactory Attraction of the Mexican Fruit Fly (Diptera: Tephritidae) to Metabolites of Bacterial Species

Bacteria isolated from the Mexican fruit fly, Anastrepha ludens Loew, were identified and found to be similar to bacteria isolated from other fruit fly species. Bacteria of the same species as those identified from A. ludens were obtained from the American Type Culture Collection (ATCC). These bacteria were cultured and attractiveness to A. ludens adults was determined for the whole beer, and for filtered and autoclaved supernatants in laboratory bioassays. All bacterial cultures were attractive to A. ludens, and some were significantly more attractive than others. Autoclaved supernatants were significantly more attractive than the whole beer or filtered supernatants. Two strains of Bacillus thuringiensis (serovars finitimus and kurstaki), not previously reported to attract fruit flies, were attractive to A. ludens. In field studies, metabolites from bacterial fermentation of two cultures (ATCC #8090 and #13883) captured as many A. ludens adults as Torula yeast/borate pellets. Metabolites from these two cultures caught nearly twice as many females as males compared to about equal numbers of males and females captured by Torula yeast/borate pellets and Nulure@^R. Consistent with laboratory bioassays, metabolites from RGM-1 caught significantly fewer A. ludens adults than the metabolites from #8090 and #13883.

Volatiles production and attractiveness to the mexican fruit fly of Enterobacter agglomerans isolated from apple maggot and Mexican fruit flies

We investigated two strains of uricase (+) Enterobacter agglomerans, one isolated from the apple maggot fly (AMF) and one from the Mexican fruit fly (MFF), for 1) attractiveness to MFF, and 2) production of attractive chemicals. Regarding chemicals demonstrated attractive to the MFF, the MFF bacterial strain produced more 2,5-dimethylpyrazine, 2-phenylethanol, and indole than the AMF strain, whereas the AMF, but not the MFF strain, produced 3-hydroxybutanone. Cell types that predominated in plated subcultures varied from batch to batch resulting in variation in volatiles production, especially by the AMF strain where indole was sometimes a major component of the odor and at other times not detectable. Despite the greater production of attractive chemicals by the MFF strain, the AMF strain was consistently more attractive and the MFF strain was not different from uninoculated control plates. Statistical analyses indicated negative correlations of attractiveness with production of indole, 2,5-dimethylpyrazine, and 2-phenylethanol, and positive correlation with 3-hydroxybutanone. Results support previous findings with the Mexican fruit fly that showed combinations of attractive chemicals sometimes are not attractive.

Purine Metabolizing Capability of Enterobacter agglomerans Affects Volatiles Production and Attractiveness to Mexican Fruit Fly

We investigated two strains of Enterobacter agglomerans that differ in their ability to metabolize uric acid for (1) attractiveness to sugar-fed Mexican fruit flies, and (2) production of volatile chemicals that may be responsible for the attractiveness. The two strains were cultured on a medium that contained uric acid as the primary nitrogen source to simulate bird feces, a natural substrate for this bacterium. Active cultures of both strains were more attractive than uninoculated uric acid medium to both sexes of sugar-fed flies in wind-tunnel bioassays. The uricase(+) strain was more attractive than the uricase(−) strain to males and to females <9 days old, but not to older females. Volatiles found by solid-phase microextraction in greater amounts in headspace above active cultures of both strains than above uninoculated medium were ammonia, dimethyldisulfide, 3-methylbutanol, 2-phenylethanol, 2,5-dimethylpyrazine, and trimethylpyrazine. The uricase(+) strain produced more ammonia, dimethyldisulfide, and trimethylpyrazine than the uricase(−) strain. An additional chemical, 3-hydroxybutanone, appears to be produced exclusively by the uricase(+) strain. The uricase(−) strain produced more 2-phenylethanol than the uricase(+) strain. Differences in volatiles are consistent with the generally greater attractiveness of the uricase(+) strain compared with the uricase(−) strain as ammonia, 3-hydroxybutanone, and trimethylpyrazine have been demonstrated attractive to sugar-fed Mexican fruit flies.

Volatiles from Duck Feces Attractive to Mexican Fruit Fly

Aqueous extracts of three types of bird feces were attractive to laboratory-colony Mexican fruit flies in laboratory bioassays. Extracts of black-bellied whistling duck feces were chosen for further analysis. Duck feces extract was attractive to both sugar-fed and sugar-starved flies but was more attractive to sugar-fed flies. Protein deprivation of flies had no effect on their response. Duck feces incubated in water for 24 hr were more attractive than those incubated for longer periods. Duck feces extract was attractive at pH 5–9, but was most attractive at pH 9, indicating that more than one class of chemicals contributed to attractiveness of the feces. Major components of headspace of duck feces extracts collected by solid-phase microextraction and identified by GC-MS, GC-FID, and GC-FTD included ethanol, propanol, phenol, ammonia, low-molecular weight amines, and pyrazines. In general, chemicals containing nitrogen proved most attractive to sugar-fed flies. However, dimethylamine and 1-pyrroline were nearly equally attractive to sugar-fed and sugar-deprived flies. Two chemicals without nitrogen were attractive to sugar-deprived flies; none were attractive to sugar-fed flies. A synthetic mixture was prepared containing ammonia, methylamine, dimethylamine, trimethylamine, 1-pyrroline, phenol, and 2-ethylhexanol in amounts found in odor of duck feces extract. The synthetic mixture was 96% as attractive as duck feces extract to sugar-fed flies and 80% as attractive to sugar-deprived flies.

Mexican Fruit Fly Attractants: Effects of 1-Pyrroline and Other Amines on Attractiveness of a Mixture of Ammonia, Methylamine, and Putrescine

Several amines were tested alone and in combination with AMPu, an attractant mixture containing ammonium bicarbonate or ammonium carbonate, methylamine hydrochloride, and putrescine, for attractiveness to Mexican fruit flies (Anastrepha ludens Loew). In laboratory bioassay, 1-pyrroline, 3-pyrroline, 2-(methylamino)ethanol, spermidine, spermine, and indole-3-acetic acid were significantly more attractive than solvent controls. In orchard tests, traps baited with combinations of AMPu with dimethylamine hydrochloride, ethylamine, 2,5-dimethylpyrazine, or pyrrolidine captured fewer flies than traps baited with AMPu alone. Traps containing AMPu plus additional ammonium bicarbonate were much less attractive than AMPu alone. Combinations of AMPu with 1-pyrroline were about 50% more attractive than AMPu alone to both males and females. Combinations of AMPu with 3-pyrroline were not significantly more attractive than AMPu alone.