Characterization and insecticidal activity of two natural formulation types against the scale insect (Parlatoria ziziphi) and their biochemical effects on Citrus aurantium

Abstract

The scale insect, Parlatoria ziziphi (Lucas) (Diaspididae: Hemiptera), is one of the most serious insects in citrus orchards in Egypt. The efficiency of two different formulation types (emulsifiable concentrates (EC) and nanoemulsions) based on the essential oils Artemisia herba-alba (Asso.) (Asterales: Asteraceae) and Laurus nobilis (L.) (Laurales: Lauraceae) at two concentrations of 3 and 5\%, compared with the commercial mineral oil, Active Cable, was examined against P. ziziphi. The green formulations were named Artemisia and Laury relative to A. herba-alba and L. nobilis, respectively. The physicochemical properties of the tested formulations have been studied. All the EC formulations of the essential oils (EOs) as well as the nanoemulsions with ratios of EOs to Tween 1:1.5 (Artemisia) and 1:2 (Laury) passed all the tested characteristics. The droplet sizes of the successful nanoemulsions’ formulations by the ultrasonic emulsification were 153.7, 113.4 nm for Artemisia and 139.3, 89.4 nm for Laury at 3 and 5\% concentrations, respectively. Laury EC caused average reductions of 92.79 and 94.94\% (nymphs and females) when applied at 3 and 5\%, respectively, while the same oil prepared as nanoemulsions caused average reductions of 50.02 and 55.32\% at the same concentrations, compared with 91.74\% reduction resulted from spraying Active Cable. Moreover, Artemisia caused reduction percentages of 74.97, 91.52 for EC and 43.7, 54.01 for nanoemulsions, sprayed at 3 and 5\%, respectively. Although EC emulsions were more effective in reducing insect populations than nanoemulsion formulations, the efficiency of nanoemulsions gradually increased with time elapsed. The antioxidant activities of superoxide dismutase, catalase, and polyphenol oxidase enzymes were researched. It is recognized that insect infestations increase plant enzyme activity to defend them against insect attack. The results revealed a significant reduction of all the examined enzymes which were more obvious for EC emulsions than nanoemulsions. The EC formulations originated from the EOs, especially Laury 3\% EC and Artemisia 5\% EC, could be an alternative to the traditional insecticides for controlling the scale insect, P. ziziphi.