Behavioral Response of Unmated Female Plodia interpunctella Hübner (Lepidoptera: Pyralidae) to Synthetic Sex Pheromone Lure.

Indian meal moth, Plodia interpunctella Hübner, is an important pest of stored products in food facilities like processing plants, warehouses, and retail stores. Mating disruption, which uses synthetic pheromone to delay or prevent mating, is a relatively new management tactic for this pest but is becoming widely adopted. However, little is known about the mechanisms behind its efficacy, including how artificial pheromone impacts female behavior. Here we assay behavioral responses of two strains of unmated female P. interpunctella exposed to pheromone. Results show one strain increased the duration of calling behavior while the other decreased calling when exposed to pheromone lures. Time walking decreased, and time cleaning increased for both strains when exposed to pheromone. Time of first walking behavior was also delayed for one strain when exposed to pheromone. Females of both strains were less mobile when exposed to pheromone. These results show autodetection of pheromone by females, but also indicate that strains may vary in behavioral responses. Differing patterns of calling behavior between strains could be driven by either strain-specific genetic differences or laboratory induced effects. Decreasing calling behavior and overall movement during exposure to pheromone could enhance the effectiveness of a mating disruption program. However, increased calling by females in the presence of pheromone may be a competitive response and could increase mating success under certain scenarios. These findings suggest that artificial pheromone associated with monitoring and mating disruption programs has impacts on female behavior and warrants further study to determine the overall impacts on program effectiveness.

Long-Lasting Insecticide-Treated Netting Affects Reproductive Output and Mating Behavior in Tribolium castaneum (Coleoptera: Tenebrionidae) and Trogoderma variabile (Coleoptera: Dermestidae).

Preventing insect infestations is a critical component for establishing a pest management plan for stored-product insects. Long-lasting insecticide-treated netting (LLIN) is a potential tool to reduce insect movement by providing a chemical barrier, where insects may be able to physically pass through but ultimately die after exposure to the netting. Sublethal effects, such as reduced movement immediately after exposure and reduced ability to colonize, have been reported. Here we examine the sublethal effects of exposure to LLIN on two beetle species, Trogoderma variabile Ballion, warehouse beetle, and Tribolium castaneum Herbst, red flour beetle. We found that both female and male T. castaneum exposed to LLIN produced significantly less adult progeny than those exposed to untreated netting. Adult progeny output did not differ for T. variabile, but survivorship increased in T. variabile females exposed to LLIN. Importantly, the overall net reproductive rate was significantly decreased for both T. variabile and T. castaneum. The number of copulation attempts did not differ between males or females exposed to LLIN compared to untreated netting, but males exposed to LLIN showed increased durations of attempted and successful copulation events. This research demonstrates that the implications of LLIN exposure extend past direct mortality, with sublethal effects on reproductive output potentially increasing the effectiveness of this tool for preventing insect infestations.

Artificial Selection to a Nonlethal Cold Stress in Trogoderma variabile Shows Associations With Chronic Cold Stress and Body Size.

Extreme temperature has been used as an alternative to chemical treatments for stored product pests for years. Resistance to heat or cold treatments has not been documented in stored product insects, but repeated use of ineffective treatments could lead to adaptive tolerance. Trogoderma variabile (Dermestidae) is a common pest of stored products, and the larval stage is highly resistant to cold and destructive. We artificially selected populations by inducing chill coma at four different cold temperature treatments: 3 and 5 h at -10°C and 3 and 5 h at 0°C. Recovery time was highly heritable after selection for seven generations for decreased recovery time (cold tolerance) and increased recovery time (cold susceptibility) at all time and temperature combinations. Three replicate populations for each time and temperature combination varied substantially, suggesting different mutations in each population were probably responsible for selected phenotypes. Body size decreased in populations selected for cold susceptibility compared with those selected for cold tolerance and survivorship to long-term cold stress increased in the cold-tolerant populations compared with the susceptible populations. After the cessation of the selection experiment, cold tolerance dissipated within four generations from the populations at -10°C, but was maintained in populations exposed to 0°C. Our results suggest that warehouse beetles can adapt to cold stress quickly, but in the absence of cold stress, the proportion of cold-tolerant/susceptible individuals is quickly reduced, suggesting that some of the mutations responsible for these phenotypes may be associated with fitness costs under normal conditions.