Departament of Entomology, Instituto Aggeu Magalhães-Fiocruz, Av. Moraes Rego S/N, Recife, PE, 50740-465, Brazil.
Parasit Vectors. 2024 Sep 14;17(1):391. doi: 10.1186/s13071-024-06465-5.
Microbial larvicides containing both LysiniBacillus sphaericus and Bacillus thuringiensis svar. israelensis (Bti) insecticidal crystals can display advantages for mosquito control. This includes a broader action against larvae that are refractory to the Binary (Bin) toxin from L. sphaericus, as Bin-resistant Culex quinquefasciatus and Aedes aegypti naturally refractory larvae, which often co-habit urban areas of endemic countries for arboviruses. Our principal goal was to assess the toxicity of a combined L. sphaericus/Bti larvicide (Vectomax FG™) to Cx. quinquefasciatus (susceptible CqS and Bin-resistant CqR) and Ae. aegypti (Rocke) and to determine its persistence in the breeding sites with those larvae.
The toxicity of a combined L. sphaericus/Bti product (VectoMax FG™) to larvae was performed using bioassays, and persistence was evaluated in simulate field trials carried out under the shade, testing two label concentrations during 12 weeks. A laboratory strain SREC, established with CqS and CqR larvae, was kept during four generations to evaluate the ability of the L. sphaericus/Bti to eliminate resistant larvae.
The L. sphaericus/Bti showed toxicity (mg/L) to larvae from all strains with a decreasing pattern for CqS (LC = 0.006, LC = 0.030), CqR (LC = 0.009, LC = 0.069), and Rocke (LC = 0.042, LC = 0.086). In a simulated field trial, the larvicide showed a persistence of 6 weeks and 8 weeks, controlling larvae from all strains in containers with 100 L of water, using 2 g or 4 g per container (100 L), respectively. The treatment of SREC larvae with L. sphaericus/Bti showed its capacity to eliminate the Bin-resistant individuals using suitable concentrations to target those larvae.
Our results showed the high efficacy and persistence of the L. sphaericus/Bti larvicide to control Cx. quinquefasciatus and Ae. aegypti that might cohabit breeding sites. These findings demonstrated that such larvicides can be an effective tool for controlling those species in urban areas with a low potential for selecting resistance.
含有球形芽孢杆菌和苏云金芽孢杆菌以色列变种（Bti）杀虫晶体的微生物幼虫剂对蚊虫控制具有优势。这包括对球形芽孢杆菌二元毒素（Bin）具有抗性的幼虫的更广泛作用，因为 Bin 抗性库蚊和埃及伊蚊自然具有抗性的幼虫，它们经常共同栖息在地方性虫媒病毒病流行国家的城市地区。我们的主要目标是评估一种球形芽孢杆菌/苏云金芽孢杆菌联合幼虫剂（Vectomax FG™）对库蚊（敏感库蚊 CqS 和 Bin 抗性库蚊 CqR）和埃及伊蚊（Rocke）的毒性，并确定其在含有这些幼虫的滋生地中的持久性。
使用生物测定法评估一种球形芽孢杆菌/苏云金芽孢杆菌联合产品（VectoMax FG™）对幼虫的毒性，并在模拟现场试验中评估其在遮荫下进行的 12 周内的持久性，试验了两种标签浓度。使用实验室建立的 SREC 品系，该品系用 CqS 和 CqR 幼虫建立，经过四代繁殖，以评估球形芽孢杆菌/苏云金芽孢杆菌消除抗性幼虫的能力。
球形芽孢杆菌/苏云金芽孢杆菌对所有品系的幼虫均表现出毒性（mg/L），CqS（LC=0.006，LC=0.030）、CqR（LC=0.009，LC=0.069）和 Rocke（LC=0.042，LC=0.086）的毒性呈下降趋势。在模拟现场试验中，该杀幼虫剂在使用 2 克或 4 克/容器（100 升）时，在装有 100 升水的容器中对所有品系的幼虫的控制效果持续了 6 周和 8 周。用球形芽孢杆菌/苏云金芽孢杆菌处理 SREC 幼虫，表明其具有使用合适浓度消除 Bin 抗性个体的能力，从而针对这些幼虫。
我们的结果表明，球形芽孢杆菌/苏云金芽孢杆菌幼虫剂对控制可能共同栖息在滋生地的库蚊和埃及伊蚊具有高效性和持久性。这些发现表明，在选择抗性的潜力较低的城市地区，此类杀幼虫剂可以成为控制这些物种的有效工具。
