Field Responses of Nontarget Species to Semiochemicals of Stored-Product Bostrichidae

Abstract

While studying the potential occurrence of two stored grain bostrichid pests, Rhyzopertha dominica (F.) and Prostephanus truncatus (Horn), in wild habitats near Stillwater, OK, by using their aggregation pheromones, we observed two nontarget species responding to these semiochemicals. Field experiments were conducted from 2002 to 2005 by using Lindgren four-unit traps baited with either synthetic pheromone or natural semiochemicals produced by male bostrichids feeding on grain in small cages attached to traps to investigate responses of the nontarget species. Ethanol was tested as a possible synergist for R. dominica as part of related research. R. dominica were commonly trapped in forested areas with its synthetic and natural pheromone, but P. truncatus were not captured using its natural or synthetic pheromones. Trapping results from these experiments, in conjunction with records of the known subtropical distribution of P. truncatus, led us to conclude that it probably does not occur in Stillwater, OK. However, we captured large numbers of Zelus tetracanthus Stål (Hemiptera: Reduviidae) males by using synthetic pheromones of R. dominica, and this response was reduced by addition of ethanol. No Z. tetracanthus was caught in traps baited with natural pheromones of R. dominica. The results further suggest that Dominicalure-1, one of the pheromones of R. dominica, is attractive to Z. tetracanthus. Additionally, Prostephanus punctatus (Say), a wood-boring congener of P. truncatus, was trapped in large numbers with natural and synthetic pheromones of P. truncatus. It is likely that P. punctatus uses the P. truncatus compounds Trunc-call-1 and Tunc-call-2, or similar compounds, as pheromones. Our study further revealed that Trunc-call-1 alone is attractive to P. punctatus, and the responses were not significantly enhanced or inhibited by the addition of either ethanol or synthetic Trunc-call-2. Responses of Z. tetracanthus males to Dominicalure-1 suggest that this compound, or a structurally similar compound, plays a role in the chemical ecology of this predaceous species. Catches of Z. tetracanthus peaked in mid-April through May followed by a second peak in July through August. Numbers of P. punctatus captured in traps peaked April through May in two consecutive years.