Abstract Increasing temperatures can impair ecosystem services and the reproduction of dung beetles. We investigated the effects of increased nest temperatures on reproduction, dung burial, and the development of 2 dung beetle species (Onthophagus binodis and Digitonthophagus gazella). Three pairs of sexually mature F1-beetles at 15 days of age were housed in temperature-controlled chambers for 2 weeks. Temperature treatments of +3 °C and +5 °C above baseline (control: a diurnal temperature cycle modelled from 2019 to 2023 summer data at the beetles origin location) were applied. Fresh cattle dung was provided to feed the beetles, and the dung burial was recorded weekly. The number of broods produced, brood success, developmental days, pronotum width, and body weight of F2 progeny were recorded. Relative to the baseline treatment, brood production was reduced by 43.1% at +3 °C and 39.3% at +5 °C, with no significant difference between the 2 elevated-temperature treatments. Dung burial was 96 g/kg dry matter lower when beetles were reared at +3 °C compared to the control. Increased temperature did not affect brood success; however, the highest nest temperature reduced the development time of D. gazella by 2.45 days compared to the control or the +3 °C treatment. In addition, a mixed effect of the highest temperature was observed in the pronotum width, which was 0.49 mm smaller and 0.32 mm greater in the F2 beetles of O. binodis and D. gazella, respectively, compared to those that were reared with +3 °C. In conclusion, heat stress negatively affected brood construction, reduced dung burial and development of F2 progeny, and altered pronotum width, suggesting that climate warming may compromise dung beetle-mediated ecosystem services such as dung removal and associated nutrient cycling.
Abstract Pathogen spillover from managed to wild pollinators represents an emerging threat to global pollinator diversity. However, surveillance of microbial pathogens in tropical wild bee communities remains severely limited. We investigated Nosema ceranae detection prevalence in the orchid bee Euglossa imperialis across seasons at 2 ecologically contrasting sites in the Panama Canal corridor: a protected tropical forest and a semi-urban landscape. Using species-specific polymerase chain reaction (PCR) assays, we detected N. ceranae DNA in gut tissues of this euglossine bee. Detection prevalence was significantly higher at the protected forest site (34/44; 77.3%) than at the semi-urban site (12/38; 31.6%), with no seasonal effect observed. A literature synthesis revealed that Nosema parasites have been reported across at least 9 hymenopteran families, with N. ceranae showing the broadest distribution of reported associations among named species, including detections in managed and wild bees as well as social wasps. This study provides the first molecular detection of N. ceranae in E. imperialis and indicates that N. ceranae DNA is detectable in wild pollinator communities at 2 ecologically contrasting sites in the Panama Canal corridor. The higher detection prevalence at the forest site suggests that local spatial or ecological context may be an important correlate of exposure in this system, a hypothesis that will require testing with additional replicated sites and environmental covariates. These findings highlight the need for expanded pathogen monitoring in Neotropical pollinator communities and underscore the importance of integrating ecological surveillance with molecular diagnostics to assess emerging pathogen risks in tropical ecosystems.
Abstract Intensive agricultural production can reduce beneficial insects by limiting access to undisturbed habitat. Wildflower plantings are promoted as conservation strategies to support pollinators and natural enemies on farms, yet their effects on certain crop pests remain understudied. We evaluated whether wildflower plantings adjacent to highbush blueberry (Vaccinium corymbosum L.) fields increased natural enemy abundances and reduced Drosophila suzukii populations compared to fields without this practice. In 2019 and 2020, across 12 farms in Michigan representing 3 management types (conventional management without wildflower plantings, conventional with wildflower plantings, or no chemical pest management), we quantified natural enemies, monitored adult D. suzukii abundance and fruit infestation, and measured removal of D. suzukii pupae. Unsprayed fields supported the highest natural enemy abundance and pupal removal but also had the highest D. suzukii abundance. There was some limited evidence for wildflower plantings increasing natural enemies, such as post-harvest, but overall, there was no significant difference between conventionally managed sites with and without wildflower plantings, and no impact on D. suzukii pupal removal. Additionally, wildflower plantings increased D. suzukii adult abundances post-harvest and in the wildflower plantings compared to mown field margins. Fruit infestation generally remained low in conventionally managed fields irrespective of wildflower plantings. Together, these results suggest that wildflower plantings only provide limited benefits for natural enemies and do not aid in D. suzukii control. Though typically established for pollinators, understanding how habitat enhancements impact particular pests of concern is essential for designing strategies tailored to specific production systems.
Abstract Parasitoid hymenopterans are highly valuable pest control agents. Despite their necessity within the agriculture industry, they remain one of the most understudied groups of insects. Non-crop habitats adjacent to farmland provide critical ecological services for these beneficial insects and can act as a corridor from uncultivated land to fields; this interaction is a form of edge effect. Here, we evaluate how 3 types of non-crop field edges affected the diversity, richness, and abundance of parasitoid hymenopterans at varying edge distances in canola (Brassica napus L.; Brassicales: Brassicaceae). We also compiled all sampled genera into a survey of parasitoid Hymenoptera found in southern Alberta canola. We conclude: (1) non-crop boundaries have a weak effect on parasitoid communities within our study system; (2) variability in parasitoid diversity and composition was most pronounced among farms, suggesting a dominant role of farm management practices; (3) parasitoid diversity is highest at edge boundaries and decreases toward the field interior; (4) Diolcogaster spp. (Hymenoptera: Braconidae)—predominantly Diolcogaster claritibia Papp, first reported in Canada in 2014—was the dominant group of parasitoids in these fields, comprising 74% of collected specimens. Overall, the composition of parasitoid communities is likely more sensitive to individual farm management practices or landscape composition and configuration, rather than to the type of bordering non-crop habitat. Further research is needed to determine which of these farm-level drivers are influencing parasitoid communities.
Abstract Parasitoids depend on chemical cues to locate and parasitize their hosts, and flowering plants and essential oils may enhance this process within conservation biological control (CBC) strategies. This study aimed to evaluate the chemotactic responses of Trichogramma pretiosum (Riley) (Hymenoptera: Trichogrammatidae) females and parasitism rates in the presence of components associated with a Brassica oleracea var. acephala (L.) cropping system: the flowering plant Lobularia maritima (L.) (sweet alyssum), the essential oil of Corymbia citriodora Hook (EOCC) (Myrtales: Myrtaceae), eggs of Plutella xylostella (L.) (Lepidoptera: Plutellidae), and the parasitoid T. pretiosum, tested either individually or in combination. In a double-choice olfactometer, sweet alyssum was attractive to T. pretiosum females, while cabbage exhibited a repellent effect. Host eggs and EOCC, when tested individually, did not attract the parasitoid. The combination of cabbage + eggs increased attractiveness, which was further enhanced by adding EOCC. Laboratory parasitism bioassays showed no differences among the treatments with cabbage, cabbage + EOCC, and cabbage + sweet alyssum, whereas the cabbage + sweet alyssum + EOCC treatment differed significantly. Under semi-field conditions, cabbage alone resulted in lower parasitism compared with the other treatments. Emergence rates were generally high (83% to 90%), except for cabbage + sweet alyssum + EOCC, which showed reduced emergence. Overall, sweet alyssum is highlighted as a valuable companion plant for attracting T. pretiosum, and EOCC showed potential to support the management of P. xylostella, although certain combinations may negatively affect parasitoid performance.
