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Behavioral responses of male and female Rhyzopertha dominica L. (Coleoptera: Bostrichidae) to odors from pulverized wheat seeds, peanuts, cowpeas, potato tubers, acorns, and twigs from cedar and pine were compared in dual‐choice, still‐air bioassays. We investigated the reproductive success of R. dominica on five of the seven plant tissues (wheat, peanuts, cowpeas, dried potato tubers, and acorns). A field experiment was also conducted to investigate responses of dispersing R. dominica to semiochemicals emitted by live males placed on different plant species. Results showed that both sexes of R. dominica responded to plant volatiles, but responses were strongest to seeds of wheat, a plant species judged to be most suitable for beetle development due to the number of progeny produced on the plant species. Similarly, insects reared on wheat were heavier than those reared on less suitable materials. In general, behavioral responses by males to plant volatiles were faster than responses by females. Responses of conspecifics to aggregation pheromones produced by males feeding on different host materials were skewed toward females although both sexes were attracted. Male R. dominica feeding on wheat recruited more conspecifics than beetles feeding on less suitable hosts (acorns, cowpeas, peanut, and potato tubers).

Lasioderma serricorne (F.) is a serious pest of stored products that is known to be resistant to the fumigant pesticide gas phosphine. This study investigated resistance in populations from the southeastern United States, and determined if a recommended treatment schedule could kill resistant insects. A laboratory assay for adult insects was developed that used a discriminating concentration of 50 ppm phosphine applied to insects for 20 h at 25°C followed by 7 d of recovery in air. Survivors were classified as resistant. L. serricorne from six different field populations associated with stored tobacco were surveyed with the assay and all had resistant individuals. Four populations had greater than 90% of their insects resistant. Two industry-recommended treatment schedules were evaluated in laboratory fumigations against mixed life stage cultures of the four most resistant populations: the first at 200 ppm for 4 d at 25°C for controlling phosphine-susceptible L. serricorne and the second at 600 ppm for 6 d at 25°C intended to control phosphine-resistant beetles. The four populations with the highest frequency of resistant individuals from the field sampling study were not controlled by the "normal" treatment intended for susceptible insects. The higher concentration treatment greatly reduced beetle progeny from mixed-stage colony jars, but there were substantial numbers of surviving adults from all four highly resistant populations that represented unacceptable levels of control.

The lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae), a serious pest of stored cereal grains, is widely distributed and has been collected in different habitats in North America, such as those from agricultural and nonagricultural settings. Our objective was to study the dispersal distances and direction of dispersal by R. dominica after external marking using fluorescent powder, releasing marked beetles, and recapturing adults using pheromone traps in distinctively different ecological habitats, wooded sites and open grasslands, for 2 consecutive yr. The recapture rate of marked beetles ranged from 6 to 26% in both sites and was generally higher in the wooded site than the open field site for both years. There was a significant difference in dispersal distances between wooded and open sites. Mean dispersal distances in the wooded site ranged from 337 to 375 m, whereas in the open site, they varied from 261 to 333 m. Trap captures for both marked and feral beetles were related to the ambient temperature such that increase in trap captures occurred with increasing temperature. Significant differences were observed for directional movement of R. dominica in both sites and indicated that most beetles dispersed in the northwest direction. Correlation analyses showed that the relationship between numbers of marked-released-recaptured beetles significantly decreased with increasing trap distances. Understanding dispersal distances and directions provide insight to flight behavior of R. dominica and to the relationship between ecologically diverse breeding habitats. Knowledge of R. dominica habitat ecology outside of grain storage facilities may be useful in designing suitable management tactics to minimize the onset of infestations in grain storages.