Insecticidal control of Asian citrus psyllid Diaphorina citri (Hemiptera: Psyllidae)

Abstract

The Asian citrus psyllid (ACP) Diaphorina citri vectors the bacterium Candidatus Liberibacter asiaticus, the causal organism of “huanglongbing” (HLB) or citrus greening disease. Therefore, ACP control is critical to management of HLB. Foliar ground applications of newly developed, experimental and commonly used insecticides alone or with adjuvants were evaluated for their effectiveness against ACP control in 13-year-old Citrus sinensis (L.) Osbeck ‘Valencia’ orange trees during the growing season. Signifi cantly more psyllid adults were observed for one month on untreated trees compared to trees treated with phosmet (Imidan® 70 W at 1 and 1.5 lb/acre) alone or with azadirachtin (Azadirect ® 8 oz/acre), GWN 1708 (16, 24, and 30 oz/acre) with 435 Oil, fenpropathrin (Danitol® 2.4 EC 16 oz/acre), and methidathion (Supracide® 2 E at 1 qt/acre). The high rate of phosmet and the medium and high rates of GWN 1708 provided relatively better control compared to the low rates. Azadirachtin alone or with phosmet was not effective. In another study, spinetoram (Delegate WG 4 oz/acre) + Copper Hydroxide with 435 Oil or Induce, a non-ionic surfactant, Danitol 2.4 EC (16 oz/acre), Chlorpyrifos EW (5 pts/acre), and zeta-cypermethrin (Mustang® 1.5 EC 4.3 oz/acre) were all equally effective and reduced psyllid adults for 24 days after treatment (DAT) compared to untreated control whereas spinetoram alone was effective through 17 DAT. Both 435 Oil and Induce, a non-ionic surfactant, appeared to increase the efficacy of Delegate. Treatment effects on adults were more long lasting than those seen on immature ACP. However, these effects were much shorter lived compared to previous studies when foliar sprays were made during the dormant winter period when adult numbers were low and trees were not growing new shoots for psyllid reproduction. Therefore, growers are encouraged to target adult psyllids by making effective foliar applications during winter and prior to anticipated new growth during the growing season based on monitoring.