Cumulative effects of climate and landscape structure on Bombus assemblages within agricultural fields throughout the U.S.

Study Extent

see Methods

Sampling

Methods: Pest monitoring traps were placed by state cooperators within agricultural fields across diverse regions in the U.S. as part of early-detection surveys for invasive lepidopterans following Spears et al. (2016) and U.S. Department of Agriculture, Animal and Plant Health Inspection Service, Cooperative Agricultural Pest Survey approved methods for pest surveillance (CAPS, 2022). This study included a total of 434 fields throughout Florida, Indiana, Kansas, Kentucky, Maryland, South Carolina, Utah, Virginia, and West Virginia from 2018 to 2020, where the number of sites varied by state, year, and target pest (Table 3–1). Target pests included Christmas berry webworm (CBW, Cryptoblabes gnidiella Milliere, 1867), cotton cutworm (CC, Spodoptera litura Fabricius, 1775), Egyptian cottonworm (EC, Spodoptera littoralis Boisduval, 1833), golden twin spot moth (GTS, Chrysodeixis chalcites Esper, 1789), Old World bollworm (OWB, Helicoverpa armigera Hübner, 1808), and silver Y moth (SYM, Autographa gamma Linnaeus, 1758). Multi-colored (green canopy, yellow funnel, and white bucket) bucket traps (International Pheromone Systems, Cheshire, UK) were placed 20 m apart and hung 1.5 m above the ground along the edge of vegetable or other commodity crop fields (e.g., alfalfa, corn, small grain). Each trap contained a pheromone lure for a single target pest inside the lure basket of the trap canopy. An insecticide strip (Hercon Vaportape II: 10% dimethyl 2,2-dichlorovinyl phosphate, Hercon Environmental Corporation, Emigsville, PA) and a small, cellulose sponge were placed inside each bucket to kill the captured insects and absorb rainwater, respectively. Insecticide strips and pheromone lures for CBW, GTS, OWB, and SYM were replaced every 28 days, whereas pheromone lures for CC and EC were changed every 84 days. Although the collection period for traps varied by state, most traps were serviced biweekly (monthly in Kentucky) from May to August, but some states extended the trapping season based on the period of expected pest activity (Table 3–1). Since lure comparisons were not the intent of this study (but see Spears et al., 2016), trap data were combined by study site and collection period.

Method steps

1. Trap contents were screened for target pests by state cooperators, and then all non-target captures (bycatch) were sent to the Utah State University Biology Department. Bombus were separated from all other non-target specimens and then stored in a freezer at -18˚C until they could be pin-mounted, labeled, and identified to species using taxonomic keys (Colla et al., 2011; Koch et al., 2012; Williams et al., 2014).

1. Hymenoptera

Bombus assemblages within agricultural fields throughout the U.S.

1. Bombus
   rank: genus

Eastern US States.