Field evaluation of <i>Maqs</i>^® and <i>Api-Bioxal</i>^® for late summer control of <i>Varroa</i> mite infestation in Northeastern Italy

The study evaluates the efficacy and effects of two organic acid-based miticides (Maqs® and Api-Bioxal®) used in late summer to reduce the population of Varroa destructor mites in colonies of Apis mellifera ligustica. The study took place in Albaredo d’Adige (Verona, Northeastern Italy). Twenty-six honey bee colonies, divided into four groups, were used for the experiment. Miticide efficacy, average daily mortality rate of adult bees, and number of bees present in the hives at specific timeframes were evaluated. The average daily efficacy of Maqs®’s miticide proved to be 96.8% compared to 93.4% for Api-Bioxal® combined with queen caging. High adult honey bee mortality was recorded after treatment with Maqs®, showing that average daily mortality was 82.4% higher than natural daily mortality. Daily mortality for Api-Bioxal® and queen caging was instead 30.1% lower than in non-treated colonies. The average decrease in the colony population of the treated groups was higher in the Maqs® (–38%) than in the Api-Bioxal® group (–28%). The fall in the latter was comparable to the values recorded in the control groups (–23% in the Api-Bioxal and –24% in the Maqs® control groups). Both veterinary medicinal products were effective for the control of V. destructor mite populations in late summer. However, the important negative effects recorded in the Maqs® group discourage the use of this miticide in geographical and climatic conditions of the type described in this study. Api-Bioxal® in combination with queen caging did instead confirm its efficacy and reliability for controlling the infestation in Northeastern Italy.