Table_1_Are fungicides a driver of European foulbrood disease in honey bee colonies pollinating blueberries?.XLSX

IntroductionBlueberry producers in Canada depend heavily on pollination services provided by honey bees (Apis mellifera L.). Anecdotal reports indicate an increased incidence of European foulbrood (EFB), a bacterial disease caused by Melissococcus plutonius, is compromising pollination services and colony health. Fungicidal products are commonly used in blueberry production to prevent fungal diseases such as anthracnose and botrytis fruit rot. Pesticide exposure has been implicated in honey bee immunosuppression; however, the effects of commercial fungicidal products, commonly used during blueberry pollination, on honey bee larval susceptibility to EFB have not been investigated.
MethodsUsing an in vitro infection model of EFB, we infected first instar honey bee larvae with M. plutonius 2019 BC1, a strain isolated from an EFB outbreak in British Columbia, Canada, and chronically exposed larvae to environmentally relevant concentrations of fungicide products over 6 days. Survival was monitored until pupation or eclosion.
ResultsWe found that larvae chronically exposed to one, two, or three fungicidal products [Supra® Captan 80WDG (Captan), low concentration of Kenja™ 400SC (Kenja), Luna® Tranquility (Luna), and/or Switch® 62.5 WG (Switch)], did not significantly reduce survival from EFB relative to infected controls. When larvae were exposed to four fungicide products concurrently, we observed a significant 24.2% decrease in survival from M. plutonius infection (p = 0.0038). Similarly, higher concentrations of Kenja significantly reduced larval survival by 24.7–33.0% from EFB (p < 0.0001).
DiscussionThese in vitro results suggest that fungicides may contribute to larval susceptibility and response to M. plutonius infections. Further testing of other pesticide combinations is warranted as well as continued surveillance of pesticide residues in blueberry-pollinating colonies.

引言：加拿大蓝莓种植户高度依赖西方蜜蜂（Apis mellifera L.）提供的授粉服务。坊间传闻显示，由蜂房球菌（Melissococcus plutonius）引发的欧洲幼虫腐臭病（European foulbrood, EFB）发病率呈上升趋势，该病害正逐渐损害授粉服务与蜂群健康。蓝莓种植中常使用杀菌剂产品来防治炭疽病（anthracnose）与灰葡萄孢果腐病（botrytis fruit rot）等真菌病害。农药暴露已被证实会导致蜜蜂免疫抑制，但蓝莓授粉期常用的商用杀菌剂产品对蜜蜂幼虫感染EFB的易感性的影响，目前尚未有相关研究报道。
方法：本研究采用欧洲幼虫腐臭病体外感染模型，使用从加拿大不列颠哥伦比亚省EFB暴发疫情中分离得到的菌株——蜂房球菌2019 BC1，感染1龄蜜蜂幼虫，并让幼虫在6天内持续暴露于环境相关浓度的杀菌剂产品中。持续监测幼虫存活率直至化蛹或羽化。
结果：研究发现，与感染对照组相比，持续暴露于1种、2种或3种杀菌剂产品[Supra® Captan 80WDG（克菌丹，Captan）、低浓度Kenja™ 400SC（Kenja）、Luna® Tranquility（Luna）以及/或Switch® 62.5 WG（Switch）]的幼虫，其因EFB导致的存活率未出现显著下降。当幼虫同时暴露于4种杀菌剂产品时，其因蜂房球菌感染导致的存活率显著下降24.2%（p=0.0038）。类似地，高浓度Kenja处理组的幼虫因EFB导致的存活率显著降低24.7%~33.0%（p<0.0001）。
讨论：本体外实验结果表明，杀菌剂可能会提升幼虫对蜂房球菌感染的易感性，并改变其对感染的应答反应。未来需对其他农药组合开展进一步测试，并持续监测蓝莓授粉蜂群中的农药残留情况。