Abstract
Internal temperatures of honey bee hives kept at different sites in North Dakota were monitored before and during winter to evaluate the effects of treatment, in the form of exposure to commercial pollination, and location on colony health. In October, hives exposed to commercial pollination during the summer had fewer adult bees and less brood than hives kept near natural forage, as well as lower average temperatures throughout winter. Within-day temperature variability was higher among hives exposed to commercial agriculture than for those kept near natural forage, indicating reduced temperature control. Fungicides, insecticides, varroacides, and an herbicide were detected in bee bread and wax samples; no major differences were observed either in the diversity or in the concentrations of agrochemicals with the exception of chlorpyrifos at one site. Varroa and Nosema densities were low overall. Data from the same site used in successive years showed significantly more brood the first year, as well as lower temperature variability; high levels of chlorpyrifos were detected in bee bread of colonies in the second year. Colony average temperature and temperature variability were informative with respect to colony phenology and post-winter status.
Highlights
Variation in landscape exposure in summer and fall can influence the health of honey bee colonies via many mechanisms including effects from pesticide contamination, disease, or malnutrition (Simone-Finstrom et al 2016)
This study had two main goals: (1) evaluate hive temperature during overwintering to detect differences among bee hive groups subjected to different environments and (2) investigate group differences with respect to Nosema and Varroa densities and agrochemical residues
Temperature is controlled in a colony by the adult bee population (Kronenberg and Heller 1982; Stabentheiner et al 2010) so the larger the bee mass, the greater the hive volume potentially under some degree of temperature control and the higher the expected average temperature, assuming that other factors, such as the ability and desire of the colony to maintain a high temperature, are equal
Summary
Variation in landscape exposure in summer and fall can influence the health of honey bee colonies via many mechanisms including effects from pesticide contamination, disease, or malnutrition (Simone-Finstrom et al 2016). Of particular concern has been overwintering loss across space and time (Chauzat et al 2010; Genersch et al 2010; Lee et al 2015; Runckel et al 2011). Survivorship and development of brood, pre-pupae and pupae, depends on a continuous temperature of about 34–36 °C (Jones et al 2004; Stabentheiner et al 2010; Wang et al 2016). The ability of a bee colony to maintain temperature homeostasis in at least part of the hive is the result of coordinated behavior and may be indicative of colony function and health. We used continuous temperature data as a response variable to distinguish group-level effects of different migratory routes on honey bee colony health and survivorship
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