Toxicity of Organosilicone Adjuvants and Selected Pesticides to the Asian Citrus Psyllid (Hemiptera: Psyllidae) and Its Parasitoid Tamarixia Radiata (Hymenoptera: Eulophidae) (Report‪)‬

The Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is the vector of citrus greening disease (also known as huanglongbing or HLB) caused by the bacterium Candidatus Liberibacter asiaticus. Greening disease is one of the most important citrus diseases in the world (Bove 2006), causing mottling and leaf chlorosis, twig dieback, reduced production, and eventual death of the trees in 5-8 years. Infected trees produce misshapen, poorly colored, and bitter-tasting fruits, not usable for consumption (Halbert & Manjunath 2004). Diaphorina citri was first found in Florida in Jun 1998 (Hoy & Nguyen 1998) and is now established in Florida and Texas (French et al. 2001). Although the Asian citrus psyllid causes direct feeding damage to citrus (Mead 1976), its economic importance is due to transmission of the bacterium. Citrus greening was detected in Florida during 2005 and is now found in 30 counties (Florida Department of Agriculture and Consumer Services 2008). An eradication program for citrus greening disease was not developed because of its wide distribution when detected. Current management measures for greening disease in Florida citrus groves include soil application of systemic insecticides (imidacloprid and aldicarb) and multiple applications (up to 8-18) of broad-spectrum foliar insecticides (including fenpropathrin, imidacloprid, abamectin, dimethoate, carbaryl, and chlorpyrifos). Insecticides are applied during the dormant foliar season, when new flushes required for psyllid female oviposition and nymphal development are rare, with the goal of reducing adult psyllid populations prior to the first flush cycle and during the flushing season (Rogers 2008; University of Florida-IFAS Extension 2008). Trees are visually inspected and removed if infected. These approaches to managing greening disease have increased the costs of citrus production, may lead to development of insecticide resistance in D. citri, and are likely to be disruptive to natural enemies of psyllids (and other citrus pests), such as ladybeetles, lacewings, spiders (Michaud 2004), and parasitic wasps including the specialist parasitoid of the Asian citrus psyllid, Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae) (Hoy & Nguyen 1998; Hoy et al. 1999). Repeated sprays of these broad-spectrum insecticides over several years could cause secondary outbreaks of whiteflies, aphids, armored scales, and mealybugs previously held below damage thresholds by a complex of beneficial insects (University of Florida-IFAS Extension 2008). Tamarixia radiata was imported as a part of a classical biological control program and is now established in Florida (Hoy et al. 1999; Skelley & Hoy 2004).