Evaluation of Systemic Insecticides for Potato Leafhopper Control in Field-Grown Red Maple1

Systemic insecticides and application methods were evaluated in two trials that began in 2005 and 2006 for control of potato leafhopper (Empoasca fabae [Harris]) on four red maple (Acer rubrum L.) cultivars and rated annually through 2007. Treatments evaluated in this study included surface drenches of imidacloprid plus cyfl uthrin (Discus) or imidacloprid plus bifenthrin (Allectus SC), clothianidin (Arena 50WDG), dinotefuran (Safari 20SG), or thiamethoxam (Flagship 25WG); soil inserted treatments of imidacloprid formulated as an experimental tablet or as an experimental gel; or a plant root dip of Discus + Terra-Sorb hydrogel. In the 2005 trial, a one-time drench of Discus or two imidacloprid tablets signifi cantly reduced leafhopper damage to red maple for a 3-year period. In the 2006 trial, a one-time drench of Allectus, Discus, Arena, Flagship, and Safari signifi cantly reduced leafhopper damage for 2 years. In most cases, the Discus drench and root dip treatments were initially more effective than the imidacloprid tablets or the gel treatment. However, in general, the effi cacy of imidacloprid tablet or gel treatments increased in subsequent years. Two imidacloprid tablets were more effective than one. Likewise, higher imidacloprid drench rates were more effective than lower rates. Most insecticide treatments signifi cantly increased red maple trunk diameter, although this effect varied with cultivar and time. Allectus and Discus drench treatments signifi cantly increased the branch and internode length of ‘Franksred’ maple in the 2005 trial. Results of this study indicate long-term potato leafhopper control with systemic insecticides and enhanced growth in red maple. Index words: leafhopper, Empoasca fabae, Acer rubrum, neonicotinoid, insecticide, tree growth. Species used in this study: red maple (Acer rubrum L.) cultivars ‘Autumn Flame’, ‘Fairview Flame’, ‘Franksred’, and ‘October Glory’. Chemicals used in this study: experimental imidacloprid tablet formulation (currently marketed as CoreTect); experimental imidacloprid gel formulation; imidacloprid + cyfl uthrin (Discus); imidacloprid + bifenthrin (Allectus SC); clothianidin (Arena); dinotefuran (Safari); thiamethoxam (Flagship); potassium polyacrylamide acrylate copolymer (Terra-Sorb Fine Hydrogel). 1Received for publication April 4, 2008; in revised form July 29, 2008. Supported in part by The Horticultural Research Institute, 1000 Vermont Ave., NW, Suite 300, Washington DC 20005 and USDA-CSREES Evans-Allen funding. We thank the following companies for providing insecticides: Bayer Environmental Science; OHP, Inc.; Syngenta Crop Protection, Inc.; FMC Corporation; Valent USA Corporation; Arysta LifeScience Corporation; and Dow AgroSciences LLC. We also thank Arysta, Bayer, FMC, OHP, Syngenta, and Valent for providing unrestricted gifts to support research projects. 2Research Associate Professor of Entomology, Tennessee State University.