The silverleaf whitefly, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae), is a significant agricultural pest worldwide, impacting a variety of crop yields. Since the introduction of B. tabaci Mediterranean (MED) species in Brazil, limited research has measured the relative efficacy of the primary insecticides used in whitefly management. This study evaluated the susceptibility of three distinct B. tabaci MED populations to 11 insecticide active ingredients and characterized the bacterial endosymbionts within each population. The insecticides tested were acetamiprid, bifenthrin, cyantraniliprole, diafenthiuron, spiromesifen, imidacloprid, pymetrozine, pyriproxyfen, sulfoxaflor, and thiamethoxam. Results showed varying LC₅₀ and LC₉₀ values among tested insecticides and populations. Notably, populations varied in response to imidacloprid and thiamethoxam with some populations having a 6× higher tolerance. Sequencing data of endosymbionts revealed that individuals from the most susceptible B. tabaci population harbored Rickettsia and Arsenophonus, whereas these bacteria were not detected in the resistant populations. These findings highlight the need for frequent insecticide toxicity bioassays of distinct B. tabaci populations and the adoption of integrated pest management strategies to preserve the efficacy of insecticides for B. tabaci control. Additionally, the role of infection by endosymbionts to alter susceptibility should be further explored.

The American burying beetle, Nicrophorus americanus Olivier, is a federally protected insect that once occupied most of eastern North America. Adult beetles feature distinct, recognizable markings on the pronotum and elytra, and color changes with age have been observed. Among the challenges faced by research scientists and conservation practitioners is the ability to determine beetle age in the field between and including teneral (young) and senescent (old) adult stages. Using 20 (10 male and 10 female) captive-bred beetles, we characterized the change in greyscale and red, green, and blue (RGB) color channels over the lifespan of each beetle for field-aging applications. Individual beetles were photographed at set intervals from eclosion to death, and color data were extracted using open-source ImageJ Version 1.54f software. A series of linear mixed-effects models determined that red color showed the steepest decrease among all color channels in the pronotum and elytral markings, with a more significant decrease in the pronotum. The change in greyscale between the pronotum and elytral markings was visibly different, with more rapid darkening in the pronotum. The resulting pronotum color chart was tested under field conditions in Oklahoma, aging 299 adult N. americanus, and six age categories (day range) were discernable by eye: teneral (0–15), late teneral (15–31), early mature (31–45), mature (45–59), early senescent (59–76), and senescent (76–90). The ability to more precisely estimate age will improve population structure estimates, laboratory breeding programs, and potential reintroduction efforts.

Among the most immediate drivers of American burying beetle (Nicrophorus americanus Olivier) declines, nontarget toxicity to pesticides is poorly understood. Acute, episodic exposure to neonicotinoid insecticides at environmentally relevant concentrations is linked to negative impacts on beneficial terrestrial insect taxa. Beyond mortality, behavioral indicators of toxicity are often better suited to assess sublethal effects of residual concentrations in the environment. First, Nicrophorus spp. congeners were used to generate and identify a low-dose exposure rate (lethal dose 10%; LD10) from an acute, 24-hour exposure and the concentration-series was confirmed by LC–MS/MS. Next, we evaluated the effects of single and repeated low-dose (LD10 = 58.9 ng/beetle) imidacloprid exposure on N. americanus behavior (10 minutes post-dose) and mortality (10 days post-dose). Behavior parameters were analyzed using EthoVision-XT. Control N. americanus were significantly less mobile, demonstrating death-feigning, an anti-predator behavior. Single LD10 dosed N. americanus were hyperactive, traveling over 4 times farther (total distance; p = 0.03) and faster (mean velocity; p = 0.02) than controls. Single and repeated LD10 dosed N. americanus extended their wings without taking flight and flipped on their backs. All control N. americanus survived 10 days post-dose; single LD10 and repeated LD10 exhibited 30% and 50% mortality, respectively. A single LD10 exposure event was sufficient to significantly elicit greater movement and high predation risk behaviors, whereas repeated LD10 exposure did not worsen behavioral impairment but increased mortality over time. Collectively, generalized linear mixed effects models indicated that distance traveled, velocity, and extended wings were significant predictors of mortality. Recently reclassified, the federally threatened N. americanus may be at greater risk to insecticide exposure than previously thought and vulnerable to episodic, low-dose neonicotinoid exposure.