Work

Synergistic larvicidal effects of temephos and Bacillus thuringiensis israelensis against Aedes albopictus: a laboratory and field study

Year: 2026

Type: article

Abstract: Background Aedes mosquito-borne diseases, such as dengue fever, pose significant challenges to global public health. Mosquito management is regarded as one of the most critical measures to control these diseases. Temephos has been widely used for larval mosquito control, but its sustained application has resulted in the emergence of resistance in many regions in China. Bacillus thuringiensis israelensis (Bti) offers an environmentally friendly alternative, but its field efficacy against late-instar larvae is limited. Previous studies have demonstrated the synergistic potential of combining temephos and Bti. Therefore, this study aims to determine the most effective combination ratio through laboratory bioassays and to evaluate the practical efficacy of this mixed formulation under field conditions. Methods Laboratory bioassays were conducted with early fourth-instar Aedes albopictus (Skuse, 1894) larvae to determine the co-toxicity coefficient (CTC) of 3 mixed formulations (temephos: Bti = 1:1, 1:3, and 1:5). In field trials, the mixed formulation with the greatest synergistic effect was used to evaluate its insecticidal effect under field conditions. A total of 150 natural breeding containers in one village in Shaoxing City were randomly selected and assigned to 3 groups (treatment group A, treatment group B, and the control group). Two application regimens (half-monthly application at twice the 99% lethal concentration [2 × LC99] vs. monthly application at 4 × LC99) were used in the treatment groups, and larval densities were monitored over a 3-month period to assess their larvicidal effects. Results The CTC values for all three mixed formulations were 141.477, 140.299, and 150.009, respectively (all exceeding 120), and mixed formulation C (temephos: Bti = 1:5) was selected for field trials. Over the 3-month period, the standard rates of reduction in mosquito larval density were 100.00%, 100.00%, and 100.00% in group A, while group B showed reductions of 96.80%, 87.03%, and 96.79%. Both treatment groups exhibited significantly lower larval densities than the control group ( p < 0.001), while no statistically significant difference was found between them. Conclusion The combination of temephos and Bti showed a synergistic effect under laboratory conditions, and the mixed formulation demonstrated effective larvicidal activity under field conditions.

Source: Frontiers in Veterinary Science

DOI: 10.3389/fvets.2026.1930489