ARTHROPOD BIOLOGY Biology of the Armored Scale Rhizaspidiotus donacis (Hemiptera: Diaspididae), a Candidate Agent for Biological Control of Giant Reed 1 1 PATRICK J. MORAN AND JOHN A. GOOLSBY United States Department of Agriculture, Agricultural Research Service, BeneÞcial Insects Research Unit, 2413 E. Highway 83, Weslaco, TX 78596 Ann. Entomol. Soc. Am. 103(2): 252Ð263 (2010); DOI: 10.1603/AN09124 ABSTRACT The development, survival, and reproductive output of the armored scale Rhizaspidio- tus donacis Leonardi (Hemiptera: Diaspididae) were determined as part of an evaluation of this scale for biological control of giant reed, Arundo donax L. Scale crawlers produced by females collected in southern France and Spain lived for less than two d in the absence of a host. On A. donax shoots held under a diurnally variable temperature regime (15Ð26ЊC), crawlers settled on leaf collars and axillary stem bases and completed the Þrst instar within 14 d. Winged adult males emerged within six wk and lived 1.7 d in vials. Immobile adult females were observed 75 d after crawler release. Development time to adult was reduced 15% in males and 28% in females when scales were reared at a constant temperature of 26ЊC. Survival from crawler to adult was 20Ð25%. The generation time for laboratory- reared females was 170 d and their average life span was 203 d. Females from Þeld collections produced an average of 85 live crawlers, 2.7-fold more than did colony-reared females. Across 31 Þeld collections, female size was correlated to the percentage of scales that were reproductive. However, among eight collections from two Spanish sites, size varied but was not correlated to reproductive success. Peak reproduction from Þeld collections occurred between November and March, and the scale completed two generations per year. Biological information about R. donacis will aid production, release, and Þeld evaluation of this scale for biological control of invasive A. donax in North America. KEY WORDS armored scale, biology, biological control, non-native invasive grass, giant reed The armored scale family Diaspididae has Ͼ2,400 grass genera (Ben-Dov 2009). All of the 38 members members worldwide (Ben-Dov 2009), of which at of the tribe Diaspidini that feed on bamboos (grass least 200 species are pests (Miller and Davidson 1990). subfamily Bambusoideae) are restricted to bamboos Armored scales damage plants by puncturing meso- (Ben-Dov 1990), and one of three pest species on phyll and parenchyma cells and sometimes vascular sugarcane, Saccharum officinarum L., is restricted to tissues in leaves, stems, woody tissues, roots, and fruit this plant genus (Williams and Greathead 1990). Ar- with their maxillaryÐmandibular stylets. Probing and mored scales may thus have unrealized potential for nutrient removal by scales reduces and deforms plant biological control of invasive perennial grasses. growth, and in some cases causes necrotic reactions to Giant reed, Arundo donax L. (Poaceae), is a peren- saliva (McClure 1990a). Many pest species alter the nial rhizomatous grass native to Mediterranean Eu- quality of fruit or other agricultural products. Al- rope, North Africa, the Middle East, the Persian Gulf though the majority of armored scale species in North region and India. Giant reed was introduced to North America and Europe are polyphagous, with plant hosts America for erosion control, as a roof thatch, for pro- in more than one family (Balachowsky 1951, Mc- duction of woodwind instruments, and as a source of Daniel 1970, Dekle 1976, Martin-Mateo 1983, Koszt- cellulose (Perdue 1958), beginning perhaps 500 yr ago arab and Koza´r 1988, McClure 1990a, Kosztarab 1996), (Dunmire 2004). It is now known from at least 14 U.S. oligophagy may be common among armored scales states and has invaded Ͼ600 river-miles along the Rio that feed on the grass family Poaceae. For example, the Grande in Texas (Everitt et al. 2005), and 30,000 ha genus Haliaspis consists entirely of grass feeders, and throughout the Lower Rio Grande Basin (LRGB), each species is typically known from only one or two which includes Þve Mexican states (March-Mifsut and Martõ´nez-Jime´nez 2008, Yang et al. 2009). Damaging, Mention of trade names or commercial products in this article is invasive populations also occur in California (Bell solely for the purpose of providing speciÞc information and does not 1997, DiTomaso and Healy 2003, Spencer et al. 2006). imply recommendation or endorsement by the U.S. Department of Agriculture. Giant reed colonizes riparian habitats and ßoodplains, 1 Corresponding author, e-mail: [email protected]. forming large thickets characterized by high shoot March 2010 MORAN AND GOOLSBY:BIOLOGY OF R. donacis 253 Fig. 1. R. donacis life stages. (A) Crawler, dorsal (top) and ventral (bottom) views, bar ϭ 0.25 mm, 80ϫ. (B) Adult female with scale covering, ventral (top) and dorsal (bottom) views, bar ϭ 1 mm, 10ϫ. (C) Second-instar male with scale covering, ventral (top) and dorsal (bottom) views, bar ϭ 1 mm, 32ϫ. (D) Reproductively immature (right) and mature (left) adult female, bar ϭ 1 mm, 12.5ϫ. (E) Lateral node on A. donax showing “witches broom” deformity caused by heavy infestation by R. donacis. density (Bell 1997) and rapid growth (Thornby et al. scale is restricted to the genus Arundo according to 2007) fueled by high photosynthetic rates (Rossa et al. both the taxonomic literature (Balachowsky 1951, 1998) and supported by dense mats of rhizomes able Martin-Mateo 1983) and our own laboratory and Þeld to tolerate a wide range of soil, moisture and nutrient host range tests involving 40 grass species and addi- conditions (Rossa et al. 1998; Decruyenaere and Holt tional plants outside the Poaceae (Goolsby et al. 2009). 2001; Spencer et al. 2006, 2008; Thornby et al. 2007). The wide distribution of R. donacis within the Medi- Giant reed consumes economically signiÞcant vol- terranean native range of giant reed (Kirk et al. 2003), umes of water (Seawright et al. 2009) and causes and its negative effects on plant growth and vigor (A. environmental damage in riparian ecosystems (re- Kirk and J.A.G., unpublished data; Fig. 1E), also fa- viewed in Goolsby and Moran 2009 and Moran and vored its candidacy for release to control A donax in Goolsby 2009). Mechanical and chemical control North America. The broad geographic range of R. methods are available but are not feasible considering donacis suggests that it can develop and survive under the large area invaded by giant reed in the arid south- both cool-warm and constant warm rearing condi- western United States. Biological control of A. donax tions. Temperature is a key factor regulating armored in the LRGB has been initiated with a host-speciÞc scale development (McClure 1990b). The genus Rhi- stem-galling wasp, Tetramesa romana Walker (Hyme- zaspidiotus MacGillivray (Tribe Aspidiotini) includes noptera: Eurytomidae) (Goolsby and Moran 2009), 13 members (Ferris 1943) of which only the polyph- but additional agents may be needed to increase bi- agous type species, R. dearnessi Cockerell, is native to ological control impacts via attack on multiple plant the Nearctic (McDaniel 1970, Dekle 1976, Kosztarab parts (Denoth et al. 2002, Blossey and Hunt-Joshi 1996). Virtually no information is available on the 2003). biology of the (at least) six grass-feeding members of One of the agents selected for evaluation against Rhizaspidiotus (Goolsby et al. 2009), or in general for giant reed is the leaf-, stem-, and rhizome-feeding Diaspididae that feed on noncrop perennial grasses. armored scale Rhizaspidiotus donacis Leonardi The objective of this study was to characterize the (Hemiptera: Diaspididae). The Þeld host range of this immature development, survival, generation time, and 254 ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA Vol. 103, no. 2 reproductive capacity of R. donacis, to support mass tus Rosen & DeBach (Hymenoptera: Aphelinidae) rearing, Þeld release and evaluation for biological con- averaged 4.8% (95% conÞdence intervals, 1.8Ð7.9%). trol of giant reed. Samples of crawlers and immature scales (from lab- oratory colonies), females with scale covers removed (from colonies and Þeld collections), and winged Materials and Methods adult males (from colonies) were measured under an Insects. Taxonomic descriptions and illustrations of MZ16 dissecting microscope (Leica Microsystems, R. donacis are available in Ferris (1943), Balachowsky Inc., New York, NY) with a digital micrometer and (1951) and Lupo (1957). IdentiÞcations were pro- Application Suite software version 2.7.1) (Leica Mi- vided by Jean-Francois Germain (Laboratoire Na- crosystems, Inc.) at 12.5Ð80ϫ magniÞcation. tional de la Protection des Vegetaux, Unite´ Plants. A. donax rhizomes were collected from sites dÕEntomologie, UFR DÕEcologie Animale et de Zo- along the Rio Grande in San Juan (Hidalgo County) ologie Agricole, Montpellier, France). Voucher spec- and Laredo (Webb County), TX, planted in 4-liter imens have been deposited in the Entomological Col- pots by using 80% peat moss soil with perlite (ÔSun- lection (U.S. National Museum of Natural History, shine Mix No. 1Ј, Sun-Gro Horticulture, Bellevue, Smithsonian Institution, USDAÐARS Systematic En- WA) and maintained as described in Moran and tomology Laboratory, Washington, DC). Figure 1 Goolsby (2009) until they were 1 mo old. At that time, shows crawlers, the adult male and female with scale the top three to four nodes of the shoot were cut to covers, and reproductively immature and mature induce lateral shoot formation, and pots were fertil- adult females with covers removed. We hypothesized ized with2gofslow-release pellets (20Ð10-5, NÐPÐK) that R. donacis would follow a generalized lifecycle for (Osmocote, Scotts-Sierra, Marysville, OH) and2gof bisexual, viviparous Diaspididae (Koteja 1990a), micronutrient pellets (Micromax, Scotts-Sierra). Af- which begins with wandering Þrst-instar crawlers, ter 2Ð4 additional wk, when plants had 2Ð7 lateral which then settle and feed to complete the Þrst-instar shoots (10Ð30 cm in length), plants were moved to a stage, and continue feeding as second instars.