Increased toxicity of malathion diluted with heavy aromatic naphtha on adult Aedes taeniorhynchus

Area of Science:

• Entomology
• Pest Management
• Environmental Science

Background:

• Mosquitoes, particularly Aedes taeniorhynchus, pose significant public health risks.
• Ultra-low volume (ULV) ground application is a common method for mosquito control.
• The efficacy of insecticides can be influenced by diluents used in formulations.

Purpose of the Study:

• To evaluate the effectiveness of Cythion (malathion) when diluted with heavy aromatic naphtha (HAN).
• To assess the impact of HAN as a diluent on mosquito mortality rates.
• To compare the efficacy of Cythion/HAN mixtures against Cythion alone and untreated controls.

Main Methods:

• Field tests using ground ULV application of Cythion at 0.45 oz AI/acre.
• Comparison of treatments including Cythion diluted 1:4 with HAN, Cythion alone, HAN alone, and an untreated area.
• Caged adult Aedes taeniorhynchus were placed at 150 ft and 300 ft downwind from application sites.
• Tests were repeated over four nights with reversed plots; data were pooled for analysis.

Main Results:

• Cythion diluted with HAN resulted in 96% mortality at 150 ft and 49% at 300 ft.
• Cythion alone achieved 33% mortality at 150 ft and 21% at 300 ft.
• HAN alone caused 8% mortality at 150 ft, and the untreated area showed 6% mortality.
• Statistical analysis confirmed a significant increase in malathion's toxicity with the addition of HAN.

Conclusions:

• Heavy aromatic naphtha (HAN) significantly enhances the insecticidal activity of malathion against Aedes taeniorhynchus.
• The use of HAN as a diluent in ULV applications can improve mosquito control efficacy.
• Formulation with HAN is a viable strategy to increase the effectiveness of malathion-based mosquito control programs.