Physiological effect of pyriproxyfen for controlling Asian citrus psyllid in sweet orange
The aim of this study was to evaluate the efficiency of pyriproxyfen insecticide, in several doses, applied on eggs, nymphs and adults of the Asian citrus psyllid, Diaphorina citri, for the management of huanglongbing (HLB or greening) on Pêra sweet orange [Citrus sinensis (L.) Osbeck]. The treatments and concentrations were consisted of: pyriproxyfen at 0.625; 1.25; 2.50 and 3.75 g ai 100 L-1 of water, acetamiprid was used as standard at 2.00 g ai 100 L-1 and a control (without insecticide). For the laboratory bioassay, eggs of D. citri in new branches were quantified under a stereomicroscope and distributed evenly among six treatments and six replications in a completely randomized design. The evaluation of nymphs density was carried out at 1, 2, 3 and 5 days after application. In two field trials, nine new branches (three per plant) were selected for the quantification of adults, eggs and nymphs of D. citri. The statistical design was conducted in randomized blocks with four replications. The trial of 11/21/2008 tested the insecticide effects on nymphs and adults, and the trial of 11/25/2008 evaluated the effects on eggs and nymphs. Based on the results for the trials conditions, it was concluded that: 1) pyriproxyfen affected the viability of the psyllid eggs; 2) the residue of pyriproxyfen on treated branches was effective for controlling emerged nymphs; 3) the efficiency of pyriproxyfen on the inhibition of adults and nymphs emergence was above 85% at concentrations of 1.25; 2.50 and 3.75 g ai 100 L-1.