Alcohol ethoxylates significantly synergize pesticides than alkylphenol ethoxylates considering bioactivity against three pests and joint toxicity to Daphnia magna

Highlights: • AEOs had higher synergistic effects on pesticides than APEOs. • Additive index, toxicity unit, V value and isobologram methods were integrated. • Synergistic ratios and toxicities of AEOs and APEOs decreased with the EO numbers. • AEOs may be potential alternatives for APEOs in agricultural production system. Seeking alternatives for alkylphenol ethoxylates (APEOs) have been a heavily researched topic in the surfactant industry and agricultural systems. In this study, the combined effects of different ethoxylates and pesticides on the bioactivity against three pests and toxicological risks to Daphnia magna were investigated. Results showed that alcohol ethoxylates (AEOs) had higher synergistic effects on the bioactivity of pesticides against Spodoptera exigua, Agrotis ipsilon and Aphis citricola than did APEOs. In terms of the joint toxicity of the ethoxylates and pesticides to D. magna, additive index method, toxicity unit method, V value method and isobologram method were used in the tests. All of these methods indicated that the joint effects of APEOs + acetamiprid and APEOs + indoxacarb upon D. magna turned from synergism to antagonism with the increasing EO (ethylene oxide) numbers. Those of AEOs exhibited similar trends. Overall, AEOs may be potential alternatives for APEOs in agriculture as they synergize pesticides against three pests significantly more than do APEOs. However, further research should investigate the compounds' environmental risks to aquatic organisms because the AEOs were highly toxic to D. magna.