192 Noack et al.: Efficacy of Imidacloprid in the Control of T. peregrinus Arboriculture & Urban Forestry 2009. 35(4): 192–196 Efficacy of Imidacloprid in the Control of Thaumastocoris peregrinus on Eucalyptus scoparia in Sydney, Australia Ann E. Noack, Jyri Kaapro, Kathryn Bartimote-Aufflick, Sarah Mansfield, and Harley A. Rose Abstract. Thaumastocoris peregrinus, an Australian native, is a new and serious pest of urban eucalypts planted in Sydney and commercial centers of Australia. In recent years, it has spread to and attained pest status in South Afri- can Eucalyptus plantations and, more recently, has been discovered in Argentina and Uruguay. Mature Eucalyptus scopar- ia street trees, growing in a southern Sydney suburb, were microinjected with imidacloprid at three concentrations and mon- itored for three years. The abundance of T. peregrinus on treated eucalypts declined significantly compared to untreated trees over this time. Further, at the lowest concentration of chemical this insect was effectively controlled for two years. Im- idacloprid (SilvaShield® ; Bayer Environmental Science) has been registered in Australia for the control of T. peregrinus. Key Words. Eucalypt Pest; Imidacloprid; Systemic Insecticide; Thaumastocoris peregrinus; Thaumastocoridae. Thaumastocoris peregrinus is a small sap-feeding insect in the family Thaumastocoridae (Hemiptera: Heteroptera). The family contains three subfamilies with disjunct distributions. Thaicorinae is known only from Thailand; its hosts are un- known. Xylastodorinae from South America lives exclusively on palms (Cassis et al. 1999) and following its introduction to Florida in 1920, became a significant pest on royal palms (Roystonea regia) (Reinert 1975). Thaumastocorinae is dis- tributed throughout Australia (with a single specimen known from India) and its host plants are predominantly dicotyledons. Until recently, the Australian group, Thaumastocorinae, was considered rare (Cassis et al. 1999). However, during the past eight years T. peregrinus has rapidly established as a pest of some Eucalyptus species throughout metropolitan Sydney and regional towns of New South Wales, Australia. It has also be- come a significant and rapidly spreading pest of eucalypt planta- tions in South Africa (Wingfield 2007) and urban plantings of eucalypts in Pretoria (pers. comm. Simon Lawson). More re- cently, it has become established on urban eucalypts growing in Buenos Aires, Argentina (Carpintero and Dellapé 2006). Some commercial plantations of the Entre Rios Province (Argentina) and Uruguay are also infested (pers. comm. Carlos Coviella). Within Sydney, two Eucalyptus species—E. scoparia and E. nicholii—have been seriously impacted by T. peregrinus infes- tation. These trees are very common as street and garden trees within the metropolitan area and are valued for their compact stature and fast growth (Noack and Rose 2007). When heavily infested these trees display a reddening of leaves, and as the in- festation progresses, the entire canopy turns reddish yellow and the tree drops its leaves (pers. obs. A. Noack). Significant num- bers of eucalypts have been removed from the Sydney basin by local councils due to such infestations (pers. obs. A. Noack). Two mymarid wasps have been confirmed attacking the eggs of T. peregrinus in Sydney; Cleruchoides noackae and St- ©2009 International Society of Arboriculture ethynium sp. (Lin et al. 2007). Although mymarids are recogn- ised as exerting significant natural control over a large number of taxa, only a few species have been used in deliberate control programs (Huber 1986; Lin et al. 2007). Research to determine the efficacy of these wasps in controlling T. peregrinus is in its infancy but until long-term sustainable management of this pest is achieved intervention with insecticides is one solution. Imidacloprid is a chloronicotinyl insecticide that acts on the nicotinic acetylcholine receptor of invertebrates (Bai et al. 1991). It was released in the early 1990s and is regularly used to con- trol insects in a variety of situations (Smith and Smith 2000; Webb et al. 2003; Ahern et al. 2005; Poland et al. 2006; Frank et al. 2007). The impact on nontarget insects by imidacloprid has been assessed as significantly less than many other insecti- cides (Albajes et al. 2003; Kilpatrick et al. 2005) and, although research in the mid 1990s implicated imidacloprid as associated with colony collapse in the honey bee (Apis mellifera), more recent research conflicts and advances numerous other causal factors (reviewed in Devine and Furlong 2007; Oldroyd 2007). When used as a systemic, imidacloprid disperses evenly in young growing plants (Nauen et al. 1999) and trees (Lawson and Dahlsten 2003; Castle et al. 2005; Cowles et al. 2006) making it a popular and effective chemical against many hemipteran pests (Ahern et al. 2005) such as psyllids, adelgids, lace bugs, flatids, and aphids (Nauen 1995; Smith and Smith 2000; Young 2002; Szc- zepaniec and Raupp 2007). Imidacloprid has been used to control Thaumastocoridae. Howard and Stopek (1998) administered imi- dacloprid systemically, via a root drench, to control outbreak pop- ulations of royal palm bug (Xylastodoris luteolus) on royal palms in Florida and report at least three months of effective control. Environmental concerns render the systemic use of pesticides more desirable than foliar application, particularly in urban set- tings where pesticide drift is an additional problem (Lawson and Dahlsten 2003). The inaccessibility of canopies of large trees com-
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