Biological efficacy of two organophosphate insecticides against California red scale (Aonidiella aurantii Maskell) related to deposition parameters under laboratory conditions

Abstract

California red scale (Aonidiella aurantii Maskell) is a major economic pest of citrus in many countries. It is mostly controlled by organophosphate insecticides. The present work is aimed at adjusting an optimal dosage of two insecticides, in order to reduce the presence of residues on the fruit while assuring their efficacy. The paper establishes, under laboratory conditions, the relationship between the deposition characteristics of these insecticides and their efficacy. It takes into account the influence of the development stage of the scale to build curves of expected mortality against the amount of active ingredient deposition. The results demonstrate the importance of applying the insecticides in the early stages of the pest and shows that the amount of active ingredient has to be doubled or even quadruplicated when treating the adult phases (pre-pupae, young female, adult female) with respect to the amounts required for the young ones (L1 and L2).