The effect of different pH levels of deionized and standard water on the efficacy of three insecticides on Bemisia tabaci .

Water acidity is an important property that can influence the performance of pesticides Acidic or alkaline water pH can negatively influence the solubility, uptake, biological activity and hydrolysis of the pesticide molecule. The effect of water pH on the efficacy of insecticides on second instar nymph of Bemisia tabaci was determined by leaf dip method. The experiment was conducted with deionized and standard water at 4 pH levels 4, 6, 7, 9 and three insecticides as malathion, acetamiprid and spiromesifen. Based on LC50 values, there was a significant difference between the toxicity of insecticides at different pH levels. All pesticides were less effective at pH 9 compared to other pH levels. The lethal dose ratio LC50 of standard to deionized water for malathion at pH 6, acetamiprid and spiromesifen at pH 7 was statistically different. The toxicity of insecticides was affected by water type at the mentioned pH levels. Malathion performance in deionized water at pH 6 was 2.82 times higher than standard at the same pH. For acetamiprid was observed that toxicity in deionized water at pH 7 was 2.55 fold more than standard. The results also revealed that spiromesifen in deionized water with pH 7 and 6 has exhibited 2.1 and 1.85 times better efficacy compared to the same pH levels in standard D. Overall, this study showed that experimental insecticides in a specific pH have a relevant effect on Bemisia tabaci.