The Identification of Boll Weevil, Anthonomus grandis grandis (Coleoptera: Curculionidae), Genes Involved in Pheromone Production and Pheromone Biosynthesis

SIMPLE SUMMARY: The boll weevil is a destructive pest of commercial cotton throughout the Americas. An eradication program in the United States has removed the boll weevil from most of its range. However, weevil populations in South Texas remain a threat to eradicated areas. Pheromone traps are used to monitor boll weevil activity, and when a weevil is captured, eradication programs rely on malathion for control. However, the effectiveness of pheromone traps in detecting incipient boll weevil populations is reduced during certain times of the year. Additionally, human safety and environmental concerns, as well as the potential development of malathion-resistant populations, have prompted program managers to seek alternative control methods. We sequenced and compared pheromone-producing and non-pheromone-producing weevils to identify genes involved in pheromone production, which, in turn, could be an environmentally friendly way to target gene-level pest control that is specific to the boll weevil. Our results revealed genes involved in pheromone production, as well as insect development and immunity, which may be targeted for boll weevil suppression. ABSTRACT: Eradication programs for the boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), rely almost exclusively on pheromone traps to indicate the need for insecticide applications. However, the effectiveness of traps in detecting weevil populations is reduced during certain times of the year, particularly when cotton is actively fruiting. Consequently, this could result in fields becoming heavily infested with weevils. It is widely speculated that the lack of weevil captures in traps during this period is largely due to the overwhelming amount of pheromone released by weevils in the field, which outcompete the pheromone released from traps. Thus, this work sought to identify genes involved in pheromone production so that new control methods that target these genes can be explored. We conducted an RNA-seq experiment that revealed 2479 differentially expressed genes between pheromone-producing and non-pheromone-producing boll weevils. Of those genes, 1234 were up-regulated, and 1515 were down-regulated, and most had gene annotations associated with pheromone production, development, or immunity. This work advances our understanding of boll weevil pheromone production and brings us one step closer to developing gene-level control strategies for this cotton pest.