Range Expansion and Adult Flight Activity of Agrilus subrobustus (Coleoptera: Buprestidae) in Tennessee

Several Agrilus species have been introduced to the United States, presumably through trans port of infested wood packaging material associ ated with international trade (Jendek & Greben nikov 2009; Haack 2006). The most problematic exotic Agrilus in the U.S. currently is the emer ald ash borer (Agrilus planipennis Fairmaire), now found in 14 eastern U.S. states as of 2009 (Michigan State University et al. 2010). Lesser known is the arrival of A. subrobustus Saunders, which was first reported in the U.S. after collec tion of 3 specimens on purple sticky traps in northern Georgia (Westcott 2007). This exotic species is listed by United State Department of Agriculture Animal and Plant Health Inspection Service (USDA-APHIS) as "quarantine signifi cant", meaning it could require mitigative action if it is determined to have a high risk of repro ducing and subsequently spreading (Joseph F. Cavey, Branch Chief, USDA-APHIS, personal communication). Agrilus subrobustus may be limited in host plant range to its only known plant resource in Asia, the silk tree (Albizia ju librissin Durazz) (Jendek & Grebennikov 2009; Westcott 2007). However, as of the publication of this note A. subrobustus has yet to be reared from its Asian host in North America. Whether or not A. subrobustus is capable of exploiting na tive plant species as larval hosts remains unde termined. This note reports further northward extension of the known geographical range of A. subrobustus in the U.S. and gives the first sea sonal adult flight records for trap catches of this beetle in North America. Mimosa, or silk tree, was introduced to the U.S. in the 18th century by Andr? Michaux as part of a nursery established in Charleston, South Caro lina (Cothran 2004). Because Michaux cultivated mimosa from seeds, it is doubtful the plants could have been the original source of A. subrobustus in North America. Early establishment of mimosa across eastern North America, originally as a pop ular ornamental plant, then as a non-native, freely reproducing exotic plant may have en hanced the likelihood of later establishment by A. subrobustus in the United States. Though timing of its arrival is not known, it is likely to have ar rived from Asian ports in wood packaging mate rial much like Asian emerald ash borer beetle (Haack 2006). Alternatively, it may have arrived in prized ornamental mimosa trees shipped from Asia, as one hemipteran pest of the silk tree is thought to have done (Wheeler & Hoebeke 2009). In 2009, four purple panel traps were deployed along the Foothills Parkway in Blount County Tennessee as part of a broader survey of bupres tid fauna in the Great Smoky Mountains Na tional Park. Traps were 1.2 m 0.7 m purple cor rugated plastic. Two traps were positioned 10 m apart at ground level in direct sun under a row of mimosa trees, which are plentiful in the sur rounding area. The other 2 traps were placed in direct sun along a closed road next to a wooded area and about 30 m away from any mimosa trees. One of the traps was placed at ground level and the other was suspended 7 m above the first. Each trap was checked biweekly from Apr to the e d of Aug and terminated 4 weeks after the last specimen was removed. Identification of A. subrobustus adults was confirmed by Richard L. Westcott (Entomologist Emeritus, Oregon Department of Agriculture) and Henry A. Hespenheide (Professor Emeritus, University of California-Los Angeles). Voucher specimens were deposited at the Great Smoky Mountains National Park collection in Gatlin burg, TN, as well as the Otis L. Floyd Nursery Crops Research Station in McMinnville, Tennes see.