Registered and Experimental Insecticides for Control of Asian Citrus Psyllid and Citrus Leafminer on Mature Orange Trees

Abstract

The Asian citrus psyllid (ACP) Diaphorina citrivectors CandidatusLiberibacter asiaticus, a bacterium which causes Asian form of “huanglongbing” (HLB) or citrus greening disease. Feeding damage by larvae of citrus leafminer (CLM) Phyllocnistis citrellapredisposes foliage to Xanthomonas axonopodispv. citri, a bacterium that causes citrus canker disease. Insecticides are critical component for developing integrated management strategies to reduce the incidence of ACP and CLM and associated diseases. Foliar sprays of registered and experimental insecticides with or without adjuvants were evaluated on 16-year-old Citrus sinensis(L.) Osbeck ‘Valencia’ orange trees pruned to produce new growth attractive to both ACP and CLM for oviposition and development of immatures. During June–July, experimental insecticides sulfoxaflor (Closer® 240 SC, 4.28 or 5.7 oz/acre) and flupyradifurone (Sivanto® 200 SL, 10.5, 12, or 14 oz/acre) and registered insecticides fenpropathrin (Danitol® 24 EC, 16 oz/acre) and spinetoram (Delegate® 25 WG, 4 oz/acre), all applied with 435 Oil (horticultural spray oil, 2–3%), reduced ACP compared to the untreated control for about 3 weeks after treatment. Effectiveness of Closer 240 SC was enhanced with the addition of 435 Oil and of Sivanto 200 SL with both 435 Oil and Induce. During August–September, treatments of fenpropathrin (Danitol® 24 EC, 16 oz/acre), thiamethoxam (Actara 25 WG, 5.5 oz/acre), abamectin + thiamethoxam (Agri-Flex® 8.5 oz/acre) and naled (Dibrom® 8 E, 16 oz/acre) all applied with 435 Oil (2%); thiamethoxam + chlorantraniliprole (Voliam Flexi®, 7.5 oz/ acre) and fenpyroximate (Portal® 0.4 EC, 32 oz/ acre) applied alone; Mpede + AdditTM (Soap 2% + Vegetable oil 0.50%); and treatments of the bioinsecticides Chromobacterium substugaeapplied with the adjuvant Hyper-Active (0.125%) reduced ACP compared to the untreated control for about 4 weeks after treatment. New insecticides effective against ACP will broaden the range of products available to control ACP. However, 3–4 week suppression of ACP observed here is still less than 6 months seen following foliar sprays of broad-spectrum insecticides made during dormant winter period when most mature trees are not producing new growth and beneficial insects are scarce. Therefore, growers are encouraged to suppress psyllids during the dormant winter period and rely on pest monitoring results and rotation of relatively selective chemistries to treat groves during the growing season. Only Agri-Flex® + 435 Oil, Voliam Flexi® and Delegate® 25 WG + 435 Oil reduced CLM compared to untreated control for 10–12 DAT, suggesting need of insecticides to target CLM for longer duration.