To Treat or Not to Treat Bees? Handy VarLoad: A Predictive Model for Varroa destructor Load.

Hélène Dechatre,Cyril Vidau,André Kretzschmar,Pierre Moreau,Alban Maisonnasse,Samuel Soubeyrand,Maryline Pioz,Fanny Mondet,Lucie Michel,Yannick Poquet,Benjamin Basso

doi:10.3390/pathogens10060678

Abstract

The parasitic Varroa destructor is considered a major pathogenic threat to honey bees and to beekeeping. Without regular treatment against this mite, honey bee colonies can collapse within a 2–3-year period in temperate climates. Beyond this dramatic scenario, Varroa induces reductions in colony performance, which can have significant economic impacts for beekeepers. Unfortunately, until now, it has not been possible to predict the summer Varroa population size from its initial load in early spring. Here, we present models that use the Varroa load observed in the spring to predict the Varroa load one or three months later by using easily and quickly measurable data: phoretic Varroa load and capped brood cell numbers. Built on 1030 commercial colonies located in three regions in the south of France and sampled over a three-year period, these predictive models are tools designed to help professional beekeepers’ decision making regarding treatments against Varroa. Using these models, beekeepers will either be able to evaluate the risks and benefits of treating against Varroa or to anticipate the reduction in colony performance due to the mite during the beekeeping season.

Highlights

The parasite Varroa destructor is considered a major pathogenic threat to honey bees [1] and to beekeeping
Without regular efficient treatment against this mite, honey bee colonies can collapse within a 2–3-year period in temperate climates
The distribution features of the variable “phoretic Varroa” (Vpt) require dividing by 100 in order to fit the data to the interval [0, 1]

Summary

Introduction

The parasite Varroa destructor is considered a major pathogenic threat to honey bees [1] and to beekeeping. This mite is an ectoparasite affecting both adult bees and broods. The Varroa threat is not new for the beekeeping community, but with colony importations and the commerce of bees, this threat continues to increase. These circumstances favor the Varroa spread throughout territories and the world’s apiaries. This threat is all the more important given that the parasite spread is rapid [2]. The current challenge is to develop new methods to limit Varroa numbers inside colonies

Objectives

Methods

Results