HORTICULTURAL ENTOMOLOGY Comparison of Exclusion and Imidacloprid for Reduction of Oviposition Damage to Young Trees by Periodical Cicadas (Hemiptera: Cicadidae) ROBERT G. AHERN, STEVEN D. FRANK, AND MICHAEL J. RAUPP Department of Entomology, University of Maryland, 4112 Plant Science Building, College Park, MD 20742 J. Econ. Entomol. 98(6): 2133Ð2136 (2005) ABSTRACT Insecticides are traditionally used to control periodical cicadas (Homoptera: Cicadi- dae) and to reduce associated injury caused by oviposition. However, research has shown that conventional insecticides have low or variable season-long efÞcacy in reducing injury caused by cicadas. New systemic neonicotinoid insecticides provide excellent levels of control against a variety of sucking insects. We compared the efÞcacy of a neonicotinoid insecticide, imidacloprid, and a nonchemical control measure, netting, to reduce cicada injury. Netted trees sustained very little injury, whereas unprotected trees were heavily damaged. Fewer eggnests, scars, and ßags were observed on trees treated with imidacloprid compared with unprotected trees; however, the hatching of cicada eggs was unaffected by imidacloprid. KEY WORDS Magicicada, imidacloprid, oviposition, scarring, ßagging PERIODICAL CICADAS, Magicicada spp., occur throughout the eastern United States and are characterized by a prolonged subterranean developmental period that lasts either 13 or 17 yr (Marlatt 1907, Williams and Simon 1995). Periodical cicada nymphs emerge from holes in the soil beneath trees in early spring. Female cicadas injure many different species of trees by goug- ing slits 10 Ð20 cm in length in bark into which they lay eggs (Smith and Linderman 1974; White 1980, 1981; Miller and Crowley 1998). Several dozen eggs are usually laid in these eggnests, and female cicadas are capable of laying several hundred eggs during their lifetime (Forsythe 1976, White 1980, Williams and Simon 1995). Injury caused by cicada oviposition is often inconsequential to large trees and generally re- sults in pruning of branch ends and ßagging. A ßag is deÞned as a hanging, broken branch on which the leaves are dead (Smith and Linderman 1974, Miller and Crowley 1998). Young trees may be severely in- jured by female cicadas, and this injury may persist many years (Williams and Simon 1995, Miller 1997). Young trees are especially susceptible to injury by periodical cicadas because a large proportion of their branches are within the range of widths preferred by female cicadas for oviposition. Flags and scars are often more pronounced and noticeable on younger trees, increasing the need to minimize injury when- ever possible. Landscape managers and nursery per- sonnel are especially affected by emergence of peri- odical cicadas because they must protect valuable ornamental plants that are susceptible to serious in- jury (Miller 1997, Miller and Crowley 1998). Insecticides are the most common tactic used to reduce injury caused by periodical cicadas, and most investigations of insecticide efÞcacy have been con- ducted in orchard systems (Forsythe 1975, Weires and Straub 1980, Hogmire et al. 1990). These studies dem- onstrated that several classes of insecticides, including organophosphates, carbamates, and pyrethroids, pro- vided quick knockdown and some residual toxicity to adult cicadas. However, relatively few studies have examined the efÞcacy of insecticides or nonchemical approaches in reducing injury caused by ovipositing adults. A notable exception is the study by Hogmire et al. (1990) who found that only esfenvalerate provided signiÞcant protection to apple branches compared with oxamyl, methomyl, and oxythioquinox. It is note- worthy that Hogmire et al. (1990) found that netting provided the best protection from ovipositing cicadas. In landscape settings, few studies have evaluated the efÞcacy of tactics to mitigate injury caused by cicadas. In a recent study, Miller (1997) found no reduction in the number of wounds per branch of mountain ash, Sorbus spp., when trees were untreated or sprayed with bifenthrin, cyßuthrin, carbaryl, chlor- pyrifos, or ßuvalinate. Imidacloprid was the Þrst neonicotinoid insecticide to be introduced to the landscape plant market, and it is still one of the most popular materials applied in landscapes owing to its range of activity against key Hemiptera, including lacebugs, aphids, scales, psyllids, and adelgids (Sclar and Cranshaw 1996, Gill et al. 1999, Young 2002, Webb et al. 2003). Although systemic products have been used against a variety of insect pests, there are no published accounts of the efÞcacy 0022-0493/05/2133Ð2136$04.00/0  2005 Entomological Society of America