Interacting stressors matter: diet quality and virus infection in honeybee health

Abstract

Honeybee population declines have been linked to multiple stressors, including reduced diet diversity and increased exposure to understudied viral pathogens. Despite interest in these factors, few experimental studies have explored the interaction between diet diversity and viral infection in honeybees. Here, we used a mixture of laboratory cage and small semi-field nucleus hive experiments to determine how these factors interact. In laboratory experiments, we found that high-quality diets (polyfloral pollen and high-quality single-source pollen) have the potential to reduce mortality in the face of infection with Israeli acute paralysis virus (IAPV). There was a significant interaction between diet and virus infection on mortality, even in the presence of high virus titres, suggesting that good diets can help bees tolerate virus infection. Further, we found that extreme stress in the form of pollen starvation in conjunction with IAPV infection increase exiting behaviour from small experimental hives. Finally, we showed that higher-quality pollen diets have significantly higher iron and calcium content, suggesting micronutrient deficiencies could be an under-explored area of bee nutrition.

Honey Bee (Hymenoptera: Apidea) Pollen Forage in a Highly Cultivated Agroecosystem: Limited Diet Diversity and Its Relationship to Virus Resistance

“…Augmenting the amount and type of pollen can improve honey bee immunity to pathogens ( Parrinello et al 2011 , Foley et al 2012 , Di Pasquale et al 2013 ). When provided a diet composed of pollen from diverse plants or from a single plant that produces high-quality pollen, honey bee survival was improved when infected with Nosema parasite and lethal viruses ( Di Pasquale et al 2013 , Dolezal et al 2019b ). However, a diet of pollen from a single plant species of low-nutritional quality did not rescue bees from Nosema infection ( Di Pasquale et al 2013 ).…”

Ameliorative Effects of Phytochemical Ingestion on Viral Infection in Honey Bees

“…Pollen is a critical component of the bee diet, affecting many aspects of bee biology [ 68 ], including immunocompetence [ 12 ], pesticide tolerance [ 26 ], and response to virus infection. Dolezal et al [ 13 ] showed that even the quality of pollen can influence mortality rates of bees infected with viruses. The exclusion of dietary pollen, therefore, prevents the accidental masking or augmentation of any potential effects incurred by phytochemical consumption, an observation that was shared by Palmer-Young et al [ 22 ] when discussing the effects of phytochemicals on pathogen infection.…”

“…Dead bees were given priority over live bees for sampling to minimize depopulating the cages. The 36-hpi timepoint was selected as past experimentation has shown that this tends to be the point at which IAPV titers are highest within the bee without inducing lethal effects [ 13 ].…”

“…In addition to developing pharmaceutical approaches to treat viruses, there is also evidence that natural components of the honey bee diet can provide protection against pathogens. For example, the diversity and quality of pollens consumed by individual bees can have a significant effect on their ability to tolerate infections [ 12 , 13 , 14 ]. Individual secondary plant metabolites, or phytochemicals, are also routinely collected by foragers in nectar, pollen, and resins, and are typically present in honey [ 15 ].…”

Microalgae as a promising and sustainable nutrition source for managed honey bees

“…Nutritional status is among the most important modifiable determinants of honey bee health. In honey bees, malnutrition interacts with and amplifies the detrimental effects of parasites, pathogens, and pesticide exposure (Dolezal & Toth, 2018; Dolezal et al, 2019; Tosi, Nieh, Sgolastra, Cabbri, & Medrzycki, 2017). Pollen is the colony's main source of proteins, lipids, vitamins and minerals (Brodschneider & Crailsheim, 2010).…”