Roles of putrescine and 1-pyrroline in attractiveness of technical-grade putrescine to the Mexican fruit fly (Diptera: Tephritidae)

Laboratory experiments were conducted to determine if 1-pyrroline, present as a contaminant of putrescine, was responsible for the observed attractiveness of putrescine to the Mexican fruit fly, Anastrepha ludens (Loew) (Diptera: Tephritidae). Technical-grade putrescine contained 0.025% 1-pyrroline measured by gas chromatography. Putrescine purified by high performance liquid chromatography contained 0.0000053% 1-pyrroline, constituting a 99.98% reduction compared with technical-grade putrescine. Purified putrescine was more attractive than technical-grade putrescine over a range of concentrations. The amount of 1-pyrroline found in technical-grade putrescine was attractive, but less so than technical-grade putrescine at 2 concentrations. Either purified putrescine or an amount of 1-pyrroline equivalent to that in technical putrescine could substitute for technical putrescine in combinations with 2 other attractive chemicals, ammonium bicarbonate and methylamine HCl. Results indicate that putrescine more so than 1-pyrroline accounts for the attractiveness of technical putrescine but that either chemical enhances the attractiveness of ammonia and methylamine about equally.