Bava Roberto, Castagna Fabio, Palma Ernesto, Musolino Vincenzo, Carresi Cristina, Cardamone Antonio, Lupia Carmine, Marrelli Mariangela, Conforti Filomena, Roncada Paola, Musella Vincenzo, Britti Domenico
Department of Health Sciences, University of Catanzaro Magna Græcia, 88100 Catanzaro, Italy.
Interdepartmental Center Veterinary Service for Human and Animal Health, University of Catanzaro Magna Græcia, CISVetSUA, 88100 Catanzaro, Italy.
Vet Sci. 2022 Dec 9;9(12):684. doi: 10.3390/vetsci9120684.
Varroatosis is an important parasitic disease of Apis mellifera caused by the mite Varroa destructor (V. destructor). The parasite is able to transmit numerous pathogens to honeybees which can lead to colony collapse. In recent years, the effectiveness of authorized drug products has decreased due to increasing resistance phenomena. Therefore, the search for alternatives to commercially available drugs is mandatory. In this context, essential oils (EOs) prove to be a promising choice to be studied for their known acaricide properties. In this research work, the acaricide activity of EO vapours isolated from the epigeal part (whole plant) of fennel (Foeniculum vulgare sbps. piperitum) and its three fractions (leaves, achenes and flowers) against V. destructor was evaluated. The effectiveness of fumigation was studied using two methods. The first involved prolonged exposure of mites to oil vapour for variable times. After exposure, the five mites in each replicate were placed in a Petri dish with an Apis mellifera larva. Mortality, due to chronic toxicity phenomena, was assessed after 48 h. The second method aimed to translate the results obtained from the in vitro test into a semi-field experiment. Therefore, two-level cages were set up. In the lower compartment of the cage, a material releasing oil vapours was placed; in the upper compartment, Varroa-infested honeybees were set. The results of the first method showed that the increase in mortality was directly proportional to exposure time and concentration. The whole plant returned 68% mortality at the highest concentration (2 mg/mL) and highest exposure time (48 h control), while the leaves, achenes and flowers returned 64%, 52% and 56% mortality, respectively. In the semi-field experiment, a concentration up to 20 times higher than the one used in the in vitro study was required for the whole plant to achieve a similar mite drop of >50%. The results of the study show that in vitro tests should only be used for preliminary screening of EO activity. In vitro tests should be followed by semi-field tests, which are essential to identify the threshold of toxicity to bees and the effective dose to be used in field studies.
蜂螨病是由狄斯瓦螨（Varroa destructor，简称V. destructor）引起的西方蜜蜂（Apis mellifera）的一种重要寄生虫病。这种寄生虫能够将多种病原体传播给蜜蜂，进而可能导致蜂群崩溃。近年来，由于耐药现象不断增加，已获授权的药品的有效性有所下降。因此，寻找市售药物的替代品势在必行。在这种背景下，精油因其已知的杀螨特性，被证明是一种值得研究的有前景的选择。在这项研究工作中，评估了从茴香（Foeniculum vulgare sbps. piperitum）地上部分（全株）及其三个部位（叶、瘦果和花）分离出的精油蒸汽对狄斯瓦螨的杀螨活性。采用两种方法研究熏蒸效果。第一种方法是让螨虫长时间暴露于精油蒸汽中，暴露时间可变。暴露后，将每个重复样本中的五只螨虫置于装有一只西方蜜蜂幼虫的培养皿中。48小时后评估由慢性毒性现象导致的死亡率。第二种方法旨在将体外试验获得的结果转化为半田间试验。因此，设置了两层的笼子。在笼子的下层放置释放精油蒸汽的材料；在上层放置感染了狄斯瓦螨的蜜蜂。第一种方法的结果表明，死亡率的增加与暴露时间和浓度成正比。在最高浓度（2毫克/毫升）和最长暴露时间（48小时对照）下，全株的死亡率为68%，而叶、瘦果和花的死亡率分别为64%、52%和56%。在半田间试验中，全株需要比体外研究中使用的浓度高20倍才能达到类似的大于50%的螨虫掉落率。研究结果表明，体外试验仅应用于精油活性的初步筛选。体外试验之后应进行半田间试验，这对于确定对蜜蜂的毒性阈值以及田间研究中使用的有效剂量至关重要。
