Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/25/2011
Publication Date: 9/1/2011
Citation: Suh, C.P., Westbrook, J.K. 2011. Attraction of milkweed stem weevils, Rhyssomatus spp. (Coleoptera: Curculiondae), to grandlure. Southwestern Entomologist. 36:375-376. Interpretive Summary: Pheromone (grandlure) dispensers effectively attract boll weevils to traps, but also attract other weevil species which may confound pest identification. While testing standard and experimental formulations of grandlure for capture of boll weevils, substantial numbers of milkweed stem weevils were captured in the traps. Traps baited with experimental grandlure captured four times more milkweed stem weevils than those baited with standard grandlure. This novel finding could lead to development of a trap-based system for detecting and monitoring milkweed stem weevil populations, which infest several milkweed species that also serve as a critical food source for Monarch butterfly caterpillars.
Technical Abstract: A trapping study was initiated in the spring of 2010 to compare the attraction of boll weevils to standard grandlure (synthesized boll weevil pheromone) and a new experimental formulation of grandlure. Both formulations contained the same four pheromone components, but differed in the proportion of each component. During the first week of the evaluation, a considerable number of traps captured weevils that were distinctly different from boll weevils, but whose identity at that time was unknown by the authors. Specimens were sent to the Texas A&M University Insect Collection facility and were subsequently identified as milkweed stem weevils. While processing trap captures during the second week of the evaluation, it became apparent that more milkweed weevils were captured than boll weevils and the milkweed weevils appeared to exhibit an increased attraction to the experimental blend of grandlure. Overall, traps baited with the experimental blend captured four times more milkweed weevils than those baited with standard grandlure. Although little is known of the ecology of milkweed stem weevils, these weevils are considered pests of several milkweed species which also serve as critical food sources for Monarch caterpillars. As such, the attraction of milkweed stem weevils to grandlure may be of particular interest to those involved in milkweed or Monarch butterfly research. We anticipate our novel finding could lead to the development of a trap-based system for detecting and monitoring milkweed stem weevil populations.