In vivo evaluation of the efficacy of Cymbopogon citratus (lemongrass), Allium sativum (garlic), Leptospermum scoparium (manuka), and Litsea cubeba essential oils on Varroosis and Nosemosis co-infection in honey bees under field conditions

Abstract

In this study, the efficacy of four different essential oils; Cymbopogon citratus (CC, Lemongrass), Allium sativum (AS, Garlic), Leptospermum scoparium (LS, Manuka), and Litsea cubeba (LC) against mite and microsporidian infections was evaluated in hives simultaneously infested with Varroa destructor and Nosema spp. Changes in mite and microsporidian loads were analyzed to determine the biological control potential of these plant-based treatments. Forty-two hives were divided into six groups (four treatment, two control), each consisting of seven hives. Essential oils were applied to the frames four times at weekly intervals using a spray method in the treatment groups. The Nosema load was determined using the digestion method, and the Varroa load was determined using the powdered sugar method. The number of falling mites was calculated using sticky paper placed on the bottom frame of the hive. Nosemosis treatment efficacy was 57.64% (CC), 58.97% (AS), 62.54% (LS), and 66.55% (LC). For Varroa, efficacy was 77.92%, 77.77%, 75.91%, and 79.42%, respectively. All treatment groups showed significant reductions in mite numbers from day 0 to 28 (p<0.001). Sticky board counts revealed a progressive decline between days 7 and 28 in AS, LS, and LC groups (p<0.001). Nosema spore counts also significantly decreased in all treatment groups (p<0.001). In this study, essential oils were found to be effective against Varroa infestation. Chemical residues in bee products, especially honey, can be prevented by using plant extracts instead of chemical agents in Varroa infestations.