Plasma-activated water as a potential synergist to enhance the insecticidal activity of imidacloprid and flonicamid against cotton aphids

BACKGROUND: Over-reliance on and excessive use of pesticides for pest management have led to various side effects, including the rapid development of pesticide resistance. The abundant reactive species present in plasma-activated water (PAW) make it a potential alternative to pesticides for controlling crop pests. Whether PAW can truly replace pesticides or significantly reduce their usage depends on its efficacy when applied in the same manner as pesticides. RESULTS: A foliar spray bioassay that simulates the field application of pesticides was established to estimate the direct toxicity of PAW to two insecticide-susceptible and two resistant strains of cotton aphids in the presence and absence of imidacloprid or flonicamid. Spraying PAW alone only caused mortality of about 20–30% against the four cotton aphid strains, significantly lower than the effects of imidacloprid LC₂₅ dose and flonicamid LC₂₅ dose to the four strains. Spraying a mixture of PAW and imidacloprid at LC₂₅ dose or flonicamid at LC₂₅ dose resulted in significantly higher mortality rates against the four strains compared to the two insecticides diluted with pure water. Relative to pure water control, PAW and its mixtures with imidacloprid LC₂₅ dose or flonicamid LC₂₅ dose displayed no adverse effects on chlorophyll content and the photosynthetic parameters of cotton seedlings. CONCLUSION: The data obtained indicate that PAW has the potential to serve as a plant-safe synergist for enhancing the insecticidal efficacy of imidacloprid and flonicamid against both insecticide-susceptible and -resistant cotton aphids.