ARBORICULTURE ARBORICULTU & CONTENTS URBAN FORESTRY Volume 35, Issue 4, July 2009 Formerly the Journal of Arboriculture, 1975 – 2005 (Volumes 1 – 31) www.isa-arbor.com Joseph J. Doccola, Sheri L. Smith, Brian L. Strom, Arthur C. Medeiros, and Erica von Allmen Systemically Applied Insecticides for Treatment of Erythrina Gall Wasp, Quadrastichus erythrinae Kim (Hymenoptera: Eulophidae) .................................................................................. 173 Abstract. The erythrina gall wasp (EGW), believed native to Africa, is a recently described species and now serious invasive pest of Ery- thrina (coral trees) in tropical and subtropical locales. Erythrina are favored ornamental and landscape trees, as well as native members of threatened ecosystems. The EGW is a tiny, highly mobile, highly invasive wasp that deforms (galls) host trees causing severe defoliation and tree death. The first detection of EGW in the United States was in O´ahu, Hawai´i in April 2005. It quickly spread through the Hawai`ian island chain (U.S.) killing ornamental and native Erythrina in as little as two years. At risk are endemic populations of Erythrina as well as ornamental landscape species in the same genus, the latter of which have already been killed and removed from O´ahu at a cost of more than USD $1 million. Because EGW are so small and spread so quickly, host injury is usually detected before adult wasps are observed, making prophylactic treatments less likely than therapeutic ones. This study evaluates two stem-injected insecticides, imidacloprid (IMA- jet®) and emamectin benzoate, delivered through Arborjet Tree I.V.® equipment, for their ability to affect E. sandwicensis (wiliwili) canopy demise under severe EGW exposure. IMA-jet, applied at a rate of 0.16 g AI/cm basal diameter (0.4 g AI/in. dia.), was the only effective treatment for maintaining canopy condition of wiliwili trees. Emamectin benzoate, applied at a rate of ~0.1 g AI/cm basal diameter (~0.25 g AI/in. dia.), was not effective in this application, although it was intermediate in effect between IMA-jet and untreated trees. The rela- tively high concentrations of imidacloprid in leaves, and its durability for at least 13 months in native wiliwili growing on a natural, dry- land site, suggest that treatment applications against EGW can impact canopy recovery even under suboptimal site and tree conditions. Key Words: Coral Trees; Emamectin Benzoate; Erythrina sandwicensis; Imidacloprid; Tree Injection; Wiliwili. Susan D. Day, Gary Watson, P. Eric Wiseman, and J. Roger Harris Causes and Consequences of Deep Structural Roots in Urban Trees: From Nursery Production to Landscape Establishment ............................................................... 182 Abstract. Recent research has improved our understanding of how structural roots of landscape trees respond to being located abnormally deep in the soil profile. This condition is widespread among landscape trees and may originate during nursery production, at transplanting into the landscape, or when construction fill or sediment deposits bury root systems of established trees. Deep structural roots sometimes hinder successful establishment of trees, occasionally enhance establishment, and oſten have little or no effect on growth or survival. When trees respond to deep structural roots, effects are sometimes observed when root collars are as little as 7.5 cm (3 in) deep. In some cases, deep structural roots are implicated in girdling root formation, but research in this area is quite limited. This review describes scientific progress in our understanding of deep structural roots and encompasses their history, causes, and significance, as well as interdisciplinary efforts to address deep planting and tree response during establishment to deep structural roots. A theoretical model of short-term tree response to deep structural roots is presented that helps explain these conflicting outcomes and provides a decision framework for practitioners evaluating trees with deep structural roots. Key Words. Buried Roots; Deep Planting; Girdling Roots; Propagation; Root Architecture; Root Morphology; Urban Forestry. Ann E. Noack, Jyri Kaapro, Kathryn Bartimote-Aufflick, Sarah Mansfield, and Harley A. Rose Efficacy of Imidacloprid in the Control of Thaumastocoris peregrinus on Eucalyptus scoparia in Sydney, Australia ...................................................................................................................... 192 Abstract. Thaumastocoris peregrinus, an Australian native, is a new and serious pest of urban eucalypts planted in Syd- ney and commercial centers of Australia. In recent years, it has spread to and attained pest status in South African Euca- lyptus plantations and, more recently, has been discovered in Argentina and Uruguay. Mature Eucalyptus scoparia street trees, growing in a southern Sydney time. Further, at tored for three years. The abundance of T. peregrinus on treated eucalypts declined significantly compared to untreated trees over this the lowest concentration of chemical suburb, were microinjected with imidacloprid this insect was effectively controlled for two years. at three concentrations and moni- Imi- dacloprid (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. ©2009 | International Society of Arboriculture | ISSN:1935-5297
July 2009
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