How the Infestation Level of Varroa destructor Affects the Distribution Pattern of Multi-Infested Cells in Worker Brood of Apis mellifera.

Ignazio Floris,Michelina Pusceddu,Alberto Satta

doi:10.3390/vetsci7030136

Ignazio Floris, Michelina Pusceddu + Show 1 more

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https://doi.org/10.3390/vetsci7030136

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Journal: Veterinary sciences	Publication Date: Sep 17, 2020
Citations: 7	License type: CC BY 4.0

Affiliation: University of Sassari

Abstract

The mite Varroa destructor, the main ectoparasite of honey bees, is a threat to apiculture worldwide. Understanding the ecological interactions between Varroa and honeybees is fundamental for reducing mite impact in apiaries. This work assesses bee colonies with various Varroa infestation levels in apiaries to determine: (1) the relationship between multi-infested brood cells and brood infestation level, (2) the damage caused by Varroa to parasitized honey bee pupae, and (3) mite reproduction rate at various infestation levels. Data were collected from 19 worker brood combs, each from a different colony, ranging from 160 to 1725 (mean = 706) sealed cells per comb. Mite distribution was aggregated, ranging from about 2% to 74% infested cells per comb. The percentage of cells invaded by one, two, three, four, or more than four foundress mites, as a function of infestation level, was estimated by five highly significant (p < 0.0001) second-degree polynomial regression equations. The correction factors found could increase the precision of prediction models. Varroa fertility and adult bee longevity decreased as multi-infestation levels increased, and the implications of this relationship are discussed. Finally, these findings could improve sampling methods and the timing of mite treatments in apiaries, thus favoring sustainable management strategies.

Highlights

The parasitic mite Varroa destructor was originally confined to the Eastern honey bee Apis cerana [1]
This work assesses bee colonies with various levels of natural infestations by Varroa in apiaries to determine: (1) the relationship between multi-infested brood cells and brood infestation level, (2) the damage caused by Varroa to parasitized honey bee pupae in terms of bee longevity, and (3) the effect of infestation level on mite reproduction rate
The infestation level of Varroa ranged from 1.7% to 74.3% in the inspected combs, and the mean number of foundress mites per infested cell varied from 1 to 2.8 (Table 1)

Summary

Introduction

The parasitic mite Varroa destructor was originally confined to the Eastern honey bee Apis cerana [1]. Some studies have shown an aggregated distribution of Varroa in the brood [19,20], associated with increases in multi-infestation as population density grows, with consequent effects on mite development and reproduction rate, as well as on the extent of damage to bee colonies. It is important to highlight that in environmental conditions favorable for the constant presence of brood in the hives throughout seasons, such as in the Mediterranean area, it is crucial to correctly estimate the percentage of cells infested by one or more mites [34] This allows for the definition of more realistic simulation models of the development dynamic of Varroa, in line with its statistical spatial distribution, promoting more sustainable and efficient mite control. Our findings could favor sustainable management strategies by improving predictive models, sampling methods, and timing of mite treatments in apiaries

Materials and Methods

Results

Discussion