Both ecosystem function and agricultural productivity depend on services provided by bees; these services are at risk from bee declines which have been linked to land use change, pesticide exposure, and pathogens. Although these stressors often co-occur in agroecosystems, a majority of pollinator health studies have focused on these factors in isolation, therefore limiting our ability to make informed policy and management decisions. Here, we investigate the combined impact of altered landscape composition and fungicide exposure on the prevalence of chalkbrood disease, caused by fungi in the genus Ascosphaera Olive and Spiltoir 1955 (Ascosphaeraceae: Onygenales), in the introduced solitary bee, Osmia cornifrons (Radoszkowski 1887) (Megachilidae: Hymenoptera). We used both field studies and laboratory assays to evaluate the potential for interactions between altered landscape composition, fungicide exposure, and Ascosphaera on O. cornifrons mortality. Chalkbrood incidence in larval O. cornifrons decreased with high open natural habitat cover, whereas Ascosphaera prevalence in adults decreased with high urban habitat cover. Conversely, high fungicide concentration and high forest cover increased chalkbrood incidence in larval O. cornifrons and decreased Ascosphaera incidence in adults. Our laboratory assay revealed an additive effect of fungicides and fungal pathogen exposure on the mortality of a common solitary bee. Additionally, we utilized phylogenetic methods and identified four species of Ascosphaera with O. cornifrons, both confirming previous reports and shedding light on new associates. Our findings highlight the impact of fungicides on bee health and underscore the importance of studying interactions among factors associated with bee decline.

Threats to bee pollinators such as land use change, high pesticide risk and reduced floral diet diversity are usually assessed independently, even though they often co-occur to impact bees in agroecosystems. We established populations of the non-native mason bee Osmia cornifrons at 17 NY apple orchards varying in proportion of surrounding agriculture and measured floral diet diversity and pesticide risk levels in the pollen provisions they produced. We used path analysis to test the direct and indirect effects of different habitats, diet diversity and pesticide risk on emergent female offspring number and weight. High proportions of agricultural habitat surrounding bee nests indirectly reduced the number of female offspring produced, by reducing floral diet diversity in pollen. When the proportion of agriculture surrounding bee nests was high, bees collected increased proportions of Rosaceae in their pollen provisions, which marginally (0.05 p < 0.1) increased fungicide risk levels in pollen. This, in turn, marginally reduced female offspring weight. In contrast, female offspring weight increased as proportions surrounding open habitat (wildflowers, grassland and pasture) increased, but this effect was not influenced by proportion Rosaceae or fungicide risk levels in pollen. Synthesis and applications. Threats to bee health such as land use change, pesticide exposure and changes in pollen diet composition are often studied in isolation. However, our results suggest that these threats can simultaneously influence one another to impact bee populations in the agroecosystems where we rely on them for pollination. By replacing surrounding agricultural habitats with more natural habitats, such as grasslands and pastures, we can increase floral diet diversity and reduce pesticide exposure in bee-collected pollen, resulting in healthier mason bee populations in apple orchards.

The idea that noncrop habitat enhances pest control and represents a win-win opportunity to conserve biodiversity and bolster yields has emerged as an agroecological paradigm. However, while noncrop habitat in landscapes surrounding farms sometimes benefits pest predators, natural enemy responses remain heterogeneous across studies and effects on pests are inconclusive. The observed heterogeneity in species responses to noncrop habitat may be biological in origin or could result from variation in how habitat and biocontrol are measured. Here, we use a pest-control database encompassing 132 studies and 6,759 sites worldwide to model natural enemy and pest abundances, predation rates, and crop damage as a function of landscape composition. Our results showed that although landscape composition explained significant variation within studies, pest and enemy abundances, predation rates, crop damage, and yields each exhibited different responses across studies, sometimes increasing and sometimes decreasing in landscapes with more noncrop habitat but overall showing no consistent trend. Thus, models that used landscape-composition variables to predict pest-control dynamics demonstrated little potential to explain variation across studies, though prediction did improve when comparing studies with similar crop and landscape features. Overall, our work shows that surrounding noncrop habitat does not consistently improve pest management, meaning habitat conservation may bolster production in some systems and depress yields in others. Future efforts to develop tools that inform farmers when habitat conservation truly represents a win-win would benefit from increased understanding of how landscape effects are modulated by local farm management and the biology of pests and their enemies.

Pollinator populations are declining (Biesmeijer et al., 2006; Brodschneider et al., 2018; Cameron et al., 2011; Goulson, Lye, & Darvill, 2008; Kulhanek et al., 2017; National Research Council, 200...

Three new species of braconid wasps from Costa Rica are described here: Allorhogas crinitus reared from leaf galls on Protium panamense (Burseraceae), Allorhogas lacuna reared from galls on Melastomataceae and Allorhogas triopsis reared from fruit galls on Psychotria (Rubiaceae). These new species are diagnosed and compared with other species in the genus. These are the first records of an Allorhogas species associated with the plant families Burseraceae and Rubiaceae. It is the third association of Allorhogas with the family Melastomaceae.

A new plant-feeding species of braconid wasp Allorhogas minimus Centrella & Shaw is described from Heredia Province in Costa Rica. The new species is diagnosed and compared with other species in the genus. This is the first record of an Allorhogas species from fruit galls on Miconia longifolia.