Roger Schürch

Insecticides managing insect pest species in agricultural systems, including soybean, often produce lethal and sublethal non-target effects on beneficial insects, including natural enemies and pollinators. Soybeans (Fabales: Fabaceae: Glycine max (L.) Merr.) are self-pollinating, yet recent studies show that bee communities improve yield and visit blooming soybean. Here, we measured bee community health metrics (abundance, species richness, and the Shannon diversity index) in soybean fields in Columbia, Missouri, in 2019 and 2020 treated with either grower standard foliar application of a pyrethroid spray insecticide or an attract-and-kill strategy consisting of insecticidal fence netting baited with pheromone lures. We observed a significant, 1.19-fold decrease in bee abundance in attract-and-kill treatments compared to grower standard treatments across all application periods (P = 0.001). Exploratory analyses revealed that of the 5 most abundant species, only 1 (Hymenoptera: Apidae: Melissodes bimaculatus (Lepeletier, 1825)) significantly decreased in abundance in attract-and-kill settings compared to grower standard. When excluding this species from captures, the significant abundance difference between treatments disappeared (P = 0.229). Additionally, we found no significant difference between the 2 treatments for richness (P = 0.558) or diversity (P = 0.592). Yet, M. bimaculatus abundance in attract-and-kill treatments was roughly three-quarters 77% of that in grower standard treatments, a stark decline for one of the most prevalent bee species in soybean. Overall, our results suggest that M. bimaculatus alone drives the abundance decrease in attract-and-kill treatments and that diversity overall is not affected. Our study underlines the importance of understanding plant-pollinator networks when considering different pest management strategies.

Optimal foraging theory (OFT) predicts that animals employ foraging strategies that maximize a particular currency, such as net energetic efficiency, to meet their nutritional demands. Two nonexclusive patterns that arise from OFT are convergence on high‐quality resources and resource partitioning. Honey bees make collective decisions by integrating their individual foraging with social recruitment behaviors: returning foragers communicate the approximate vector to high‐quality resources using waggle dances. Because we can eavesdrop on their communications, waggle dance decoding is a valuable tool for exploring OFT predictions as it allows us to map how honey bees use landscapes. In this study, we analyzed 8049 dances from colocalized colonies across three landscapes to investigate whether neighboring colonies forage by not partitioning patches (i.e., converging their food collection on the same patches), by partitioning at the landscape level, or by partitioning at the local level. To differentiate between these three possible scenarios, we examined three metrics: (1) interdance distances between and within colonies; (2) k‐nearest neighbors; and (3) k‐means clustering. We observed no difference in the distances between dances performed by bees from the same colony compared to those from different colonies. Also, we found at each of the three field sites that dances from the same colony were not more likely to appear as close neighbors to each other. Finally, k‐means cluster analysis demonstrates that dance locations advertised by the same colony aggregated nonrandomly in the three sites, where dances from the same colony comprised a significant majority of dances within k‐means clusters and 62% of clusters consisted entirely of dances from a single colony. Together, these results support a foraging scenario where honey bees partition their foraging, but at the local level. This strategy may help limit intercolony foraging competition.

Human-induced land-use change is a well-documented driver of species decline, including bees, but its true cost may be underestimated. The effects of habitat conversion on honey bee foraging metabolic costs are not well documented. Here, we quantify the impact of land use change on the foraging of freely flying honey bees (Apis mellifera) before (2018-2019, n=382) and after (2022, n=502) their historical foraging habitat is developed. We decoded and analyzed honey bee waggle dances, through which returning foragers communicate the vector of forage. We found that bees increased (from 2.4% to 8.4%) their use of undisturbed microhabitat within the development. The small-scale developments, covering just 1% of the foraging range, nearly doubled flight distance and energy expenditure. Average distance increased from 0.69 to 1.28 kilometers (from 7 to 13 Joules). Our study updates our understanding of land development costs on local bees, revealing concrete consequences to changing land upon which pollinators depend.

Outdoor spatial mosquito repellents, such as mosquito coils or heating devices, release pyrethroid insecticides into the air to provide protection from mosquitoes within a defined area. This broadcast discharge of pyrethroids into the environment raises concern about the effect on non-target organisms. A previous study found that prallethrin discharged from a heating device did not affect honey bee (Apis mellifera L.) [Hymenoptera: Apidae] foraging or recruitment. In this second study, there was no significant difference in foraging frequency (our primary outcome), waggle dance propensity, or persistency in honey bees collecting sucrose solution between those exposed to metofluthrin from a different heating device and bees exposed to a non-metofluthrin control. One measure, waggle dance frequency, was higher in the metofluthrin treatment than the control but this outcome was likely a spurious result due to the small sample size. The small particle size of the emissions, averaging 4.43 µm, from the heated spatial repellent products, which remain airborne with little settling, may play an important role in the lack of effect found on honey bee foraging.

The red imported fire ant (RIFA),Solenopsis invicta(Buren), is a notorious, invasive species with broad impacts on ecosystems, economies, and human health. While incidental reports to the Virginia Department of Agriculture and Consumer Services (VDACS) indicate a recent range expansion in Virginia, the full extent of RIFA spread in the area is currently unknown. In this study, we examined the distribution of RIFA in Virginia using multiple data sources: (1) during the summers of 2020 and 2021, we conducted a series of prospective visual surveys along public roadways in southern Virginia, (2) we used data from multiyear VDACS infestation reports covering the period 2016–2021, and (3) we surveyed local naturalists, county extension agents, and land managers. We compared the resulting data with an earlier predictive model quantifying the potential spread of RIFA and constructed a species distribution model to explore the potential range expansion of RIFA in the United States based on new occurrence data and bioclimatic variables. RIFA was found in seven Virginia counties beyond the current federal quarantine zone, and our data show that it has spread much further than predicted 15 years ago. Our species distribution model suggests that the range of RIFA is likely to increase further under the currently projected climate change scenarios, both in Virginia and more generally across the United States, with the lower Midwest expected to be one of the most affected areas. This study provides insights into the range expansion of RIFA at the border of its suitable North American habitat and elucidates some of the environmental factors associated with its current and future spread. In doing so, it provides information to advise sound management practices and prevention efforts.

Many of the fruits that add diversity and nutrition to our diet are wholly or partially dependent upon flower‐visiting insects. For example, apples (Malus spp.) are self‐incompatible and therefore rely on insect pollinators for fruit development and seed production. Honey bees (Apis mellifera) are often migrated into these orchards when the apples are in bloom. While previous studies have focused on the impact of honey bees to fruit orchards, fewer studies have examined the reciprocal relationship of the orchards to honey bees, particularly if the bees are in the orchard for the entire foraging season, not just during bloom. Here we investigated the foraging dynamics of honey bees in apple orchards in Virginia for two full foraging seasons (April–October, 2018–2019). We decoded, mapped, and analyzed the waggle dances (n = 3710) made by returning foragers, which communicate the distance and direction from the hive to valuable resources, usually nectar or pollen. We found that bees foraged locally at after the bloom than during the bloom (29.4% vs. 18.6% in 2018 and 28.5% vs. 21.4% in 2019, respectively). Interestingly, honey bees recruited more to forests while the apples bloomed (36.9% and 25.7% in 2018 and 2019, respectively). Lastly, our odds ratio analysis, which includes a distance correction, indicates the honey bees were more than twice as likely to recruit to apple orchards in June, which is after the bloom, than in April or May, which is during the bloom. Our ground truthing revealed that post‐bloom apple orchards provided foraging opportunities on the growing understory of red and white clover (Trifolium spp.) and plantain (Plantago spp.). These data might therefore have important implications for best management practice decisions for bees located in fruit orchards.

Much like human consumers, honeybees adjust their behaviours based on resources' supply and demand. For both, interactions occur in fluctuating conditions. Honeybees weigh the cost of flight against the benefit of nectar and pollen, which are nutritionally distinct resources that serve different purposes: bees collect nectar continuously to build large honey stores for overwintering, but they collect pollen intermittently to build modest stores for brood production periods. Therefore, nectar foraging can be considered a supply-driven process, whereas pollen foraging is demand-driven. Here we compared the foraging distances, communicated by waggle dances and serving as a proxy for cost, for nectar and pollen in three ecologically distinct landscapes in Virginia. We found that honeybees foraged for nectar at distances 14% further than for pollen across all three sites (n= 6224 dances,p< 0.001). Specific temporal dynamics reveal that monthly nectar foraging occurs at greater distances compared with pollen foraging 85% of the time. Our results strongly suggest that honeybee foraging cost dynamics are consistent with nectar supply-driven and pollen demand-driven processes.

Honey bees provide invaluable economic and ecological services while simultaneously facing stressors that may compromise their health. For example, agricultural landscapes, such as a row crop system, are necessary for our food production, but they may cause poor nutrition in bees from a lack of available nectar and pollen. Here, we investigated the foraging dynamics of honey bees in a row crop environment. We decoded, mapped, and analyzed 3459 waggle dances, which communicate the location of where bees collected food, for two full foraging seasons (April–October, 2018–2019). We found that bees recruited nestmates mostly locally (<2 km) throughout the season. The shortest communicated median distances (0.474 and 0.310 km), indicating abundant food availability, occurred in July in both years, which was when our row crops were in full bloom. We determined, by plotting and analyzing the communicated locations, that almost half of the mid‐summer recruitment was to row crops, with 37% (2018) and 50% (2019) of honey bee dances indicating these fields. Peanut was the most attractive in July, followed by corn and cotton but not soybean. Overall, row crop fields are indicated by a surprisingly large proportion of recruitment dances, suggesting that similar agricultural landscapes may also provide mid‐summer foraging opportunities for honey bees.