The effect of water pH on efficiency of spirotetramat and imidacloprid against Agonoscena pistaciae under field conditions

Background and Objectives:

 Water pH is one of the most important factors that affects the inefficiency of insecticides against the common pistachio psyllid, Agonoscena pistaciae Burckardt and Lauterer (Hemiptera: Aphalaridae), as the most important pest in Iran's pistachio orchards.

 Materials and Methods:

 In this study, the effect of insecticides including spirotetramat (Monvento® SC 10%) and imidacloprid (Confidor® SC 35%) and pH reducing agents, such as Rectiphier® and Citral pH®, on the reduction of population density of eggs and nymphs of common pistachio psyllid were investigated under field conditions. The experiment was carried out as randomized complete block design with four replications. The samplings were done one day before and 3, 7, 14, 21 and 28 days after spraying.

 Results:

 The results indicated that adding Rectiphier and Citral pH to the insecticides had no significant effect on increasing the efficacy of spirotetramat and imidacloprid on eggs population of pistachio psyllid, and only on 7 days after spraying, adding of Rectiphier to imidacloprid significantly increased the efficiency of the insecticide, and reduced the amount of oviposition of A. pistaciae (91.58%). The results of the effect of different treatments on nymphs population density of A. pistaciae showed that the effect of insecticides + pH reducing agents was more than application of insecticides alone, but their effect was not significant, and only on 3 and 7 days after spraying, Rectiphier significantly increased the effect of imidacloprid. The reduction of nymphal population densities in imidacloprid + Rectiphier treatment were 90.13% and 93.23%, on those sampling dates, respectively. 

Discussion:

PH reducers (Rectifier and Citral pH) could have the potential to increase the efficacy of spirotetramate and imidacloprid or other insecticides to control A. pistaciae and produce healthy crops, reduce costs, environmental hazards and side-effects on natural enemies and to minimize application of chemical insecticides. However, more research is needed with regard to the effect of different compounds of pH reducer, different concentrations of those compounds and also the effect of these compounds on different water pH.