Resistance of the stable fly, Stomoxys calcitrans (Diptera: Muscidae), to cypermethrin in outbreak areas in Midwestern Brazil

Abstract Population explosions of the stable fly (Stomoxys calcitrans) have become a serious concern for livestock producers near sugarcane mills in some regions of Brazil due to the insect’s massive reproduction on sugarcane byproducts and waste. Despite the limited efficiency of insecticides for controlling stable fly outbreaks, producers still rely on chemical control to mitigate the alarming infestations in affected areas. This study evaluated the susceptibility of S. calcitrans populations to cypermethrin in the state of Mato Grosso do Sul, Brazil. Stable flies were tested from three field populations and two colonies, established from flies previously collected at sugarcane mills. Wild flies were collected with Nzi traps in areas of sugarcane plantations. Both wild and colonized flies were exposed to eleven concentrations of cypermethrin in impregnated filter paper bioassays. All the populations proved to be resistant to cypermethrin, with resistance factors among field populations ranging from 6.8 to 38.6. The intensive use of insecticides has led to the development of pyrethroid resistance in stable fly populations in the proximities of sugarcane mills in the state of Mato Grosso do Sul.

摘要 厩腐蝇(Stomoxys calcitrans)的种群爆发已成为巴西部分地区甘蔗加工厂周边畜牧养殖户的严重担忧，原因在于该昆虫可在甘蔗副产物与废弃物中实现大规模繁殖。尽管杀虫剂对厩腐蝇疫情的防控效率有限，但养殖户仍依赖化学防治手段，以缓解受影响区域内日益严峻的虫害问题。本研究针对巴西南马托格罗索州(Mato Grosso do Sul)的厩腐蝇种群，评估其对氯氰菊酯(cypermethrin)的敏感性。研究样本包含3个田间种群与2个繁育种群，后者由此前在甘蔗加工厂采集的厩腐蝇繁育建立。野生厩腐蝇通过Nzi诱捕器(Nzi trap)在甘蔗种植区域采集。无论是野生种群还是繁育种群，均采用浸渍滤纸生物测定法，暴露于11种梯度浓度的氯氰菊酯环境中开展测试。所有受试种群均对氯氰菊酯产生了抗药性，田间种群的抗性倍数介于6.8至38.6之间。研究结果表明，南马托格罗索州甘蔗加工厂周边区域的厩腐蝇种群，因杀虫剂的大量使用，已演化出拟除虫菊酯(pyrethroid)类抗药性。