Abstract
Honey bees are highly valued for their pollination services in agricultural settings, and recent declines in managed populations have caused concern. Colony losses following a major pollination event in the United States, almond pollination, have been characterized by brood mortality with specific symptoms, followed by eventual colony loss weeks later. In this study, we demonstrate that these symptoms can be produced by chronically exposing brood to both an organosilicone surfactant adjuvant (OSS) commonly used on many agricultural crops including wine grapes, tree nuts and tree fruits and exogenous viral pathogens by simulating a horizontal transmission event. Observed synergistic mortality occurred during the larval-pupal molt. Using q-PCR techniques to measure gene expression and viral levels in larvae taken prior to observed mortality at metamorphosis, we found that exposure to OSS and exogenous virus resulted in significantly heightened Black Queen Cell Virus (BQCV) titers and lower expression of a Toll 7-like-receptor associated with autophagic viral defense (Am18w). These results demonstrate that organosilicone spray adjuvants that are considered biologically inert potentiate viral pathogenicity in honey bee larvae, and guidelines for OSS use may be warranted.
Highlights
Honey bees are often exposed to pesticides through the residues that persist in pollen, nectar, comb wax, or on the surface of the plants in the bees’ foraging environment[9,10,11]
Recent work has shown that pesticides can negatively impact honey bee immunity, resulting in increased viral replication[17,18,19,20,21]; while attention has been given to the effects and persistence of pesticide “active” ingredients, little is known about the effects of pesticide adjuvants and other ‘inerts’ in formulations
The highest significant mortality was seen in larvae exposed to both organosilicone surfactant spray-tank adjuvant (OSS) and the viral inoculum (OSS +V) (Wald test, n = 171, Wald chi square = 6.73, p ≤ 0.0095, df = 1) with over 68.4% (+/−4.32%) of the population failing before adult eclosion (Fig. 3)
Summary
Honey bees are often exposed to pesticides through the residues that persist in pollen, nectar, comb wax, or on the surface of the plants in the bees’ foraging environment[9,10,11]. Pesticide products are generally applied as tank mixes containing more than one formulation composed of a mixture of active and inert formulants, and adjuvants meant to enhance the penetration and spread of the active ingredients[22]. While there is little publicly available information regarding their toxicity and residual presence in the environment, recent work has demonstrated that the residues of one class of inerts, organosilicone surfactant spray-tank adjuvant (OSS), are encountered by foraging bees and persist in honeybee food and wax[24]. Organosilicones (Fig. 1) are a powerful class of nonionic surfactants used in agriculture as spray tank adjuvants to enhance the penetration and spread of the active ingredient[22] They are classified as inerts, OSS’s have exhibited toxic effects on honeybees[25]. The use of insect growth regulators, fungicides, and adjuvants have been suggested as possible causes[28]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
