Effects of some conventional insecticides and insect growth regulators on different phenological stages of the white wax scale, Ceroplastes destructor Newstead (Hemiptera: Coccidae), and its primary parasitoid, Aprostocetus ceroplastae (Girault) (Hymenoptera: Eulophidae)

Abstract

The toxicity of two juvenile hormone analogues, pyriproxyfen (Nemesis®) and fenoxycarb (Insegar®), and two contact insecticides, methomyl (Lannate) and methidathion (Ultracide), was evaluated against immature stages (LI, LII, LIII) of Ceroplastes destructor Newstead in the field. The effects of these chemicals and one moulting inhibitor, triflumuron (Alsystin®), and three insecticides: methyl-parathion (Penncap-M), profenofos (Selecron) and prothiofos (Tokuthion), on Aprostocetus (= Tetrastichus) ceroplastae (Girault) were assessed in the laboratory. Development of the first and second instar nymphs of C. destructor was completely arrested by the chemicals. Less than 1% of scales sprayed with pyriproxyfen at LII stage survived to adult female. Survival to the adult stage varied significantly between chemical treatments, and between chemicals and untreated controls for scales sprayed at the LIII stage. Female fecundity, fertility and body sizes of survivors of treatments applied at the LIII stage were not significantly affected by any of the chemicals. All the chemicals exhibited high toxicity to A. ceroplastae. Only triflumuron was slightly harmful, while methomyl was the most toxic (harmful), causing 100% mortality in the first 30 min after treatment. Although all the chemicals evaluated had effectively arrested the first and second instars of C. destructor, none of them exhibited sufficient selectivity to A. ceroplastae to warrant recommendation for integrated management of C. destructor in citrus orchards in South Africa, where A. ceroplastae plays an important role.