Assessing the impact of pest monitoring traps on Bombus griseocollis (Hymenoptera: Apidae) colony growth and development
CitationChristman M, Ikerd H (2022). Assessing the impact of pest monitoring traps on Bombus griseocollis (Hymenoptera: Apidae) colony growth and development. Version 1.4. USDA-ARS Pollinating Insect-Biology, Management, Systematics Research. Occurrence dataset https://doi.org/10.15468/cg7epd accessed via GBIF.org on 2023-03-26.
DescriptionInsect traps use visual and olfactory cues to attract target pests; however, they vary in their specificity and often unintentionally capture non-target beneficial insects (bycatch), including Bombus. Concerns have been expressed that bycatch may contribute to Bombus mortality and the consequential loss of pollination services. Here, we quantified the impact of trap captures on Bombus griseocollis colony growth and development by evaluating the following four treatments: colonies paired with traps, colonies paired with traps and pheromone lures, traps and pheromone lures (but no colonies), and colonies with no trap and no lure. Trap contents were collected biweekly to determine B. griseocollis capture rates. Colony growth and development data were collected weekly by weighing colonies and recording foraging activity. Based on microsatellite polymerase chain reaction (PCR) amplification, three B. griseocollis were collected from released colonies, while the remaining five were residents within the environment. Given the low number of B. griseocollis workers collected, any differences in colony weight change and active foraging were likely not a result of pest monitoring trap captures. However, trap captures could have a greater impact by interfering with functional diversity, colony establishment, and pollination services, emphasizing the need for additional research. Building on this research will provide a more comprehensive view of the impact of pest monitoring traps on Bombus populations, which could minimize risk to pollinator populations and pollination services.
Study ExtentThis study was conducted in corn (Zea mays Linnaeus) fields in Cache and Box Elder counties in northern Utah in 2020 and 2021. Corn fields were selected following U.S. Department of Agricultural, Animal and Plant Health Inspection Service (USDA APHIS) approved methods for H. armigera pest surveillance (CAPS 2022). The four treatments occurred with five randomized replicates in 2020 (n = 20) and four in 2021 (n = 16) (N = 36). For treatments i-iii, two multi-colored bucket traps (International Pheromone Systems, Cheshire, United Kingdom) were placed in each field 5 m and 100 m away from the Bombus colony and 1.5 m above the ground. A single pheromone lure for H. armigera was placed within the lure basket of the trap canopy for treatments ii and iii. An insecticide strip (Hercon Vaportape II: 10% dimethyl 2,2-dichlorovinyl phosphate, Hercon Environmental Corportation, Emigsville, PA) and a small, cellulose sponge were placed inside each bucket to kill the captured insects and absorb rainwater, respectively. Insecticide strips and H. armigera pheromone lures were changed every 28 days throughout the collection period following USDA APHIS approved methods for pest surveillance (CAPS 2022). Trap contents were collected biweekly (treatments i–iii), and colony-only fields (treatment iv) were net surveyed (36-cm diameter insect net, Bioquip, Compton, CA) over a ten-minute time period both 5 and 100 m away from the colony to survey the resident Bombus community and identify B. griseocollis collected from the released colony while foraging.
SamplingColonies were monitored weekly from the time of deployment until September each year. Each week, the nest was weighed to the nearest gram and the number of workers entering and exiting the nest was recorded over a 10-minute time interval. Data collections occurred between 9:00 a.m. and 6:00 p.m. to comply with land and homeowner restrictions. This resulted in the concern that colony weights may be underestimated since workers forage during this time. Therefore, colonies were also weighed in the evening (between 7:00 and 9:00 pm) in 2020, and we found no significant difference in daytime vs. nighttime weights. All collected specimens were stored in a freezer (-18˚C) until they were pin-mounted, labeled, and identified to species. All captured female B. griseocollis were then subjected to DNA extraction and microsatellite PCR amplification.
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