A Taxonomic Review of the Japanese Trichogramma (Hymenoptera: Trichogrammatidae) with Descriptions of Three New Species
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Appl. Entomol. Zool. 41 (2): 247–267 (2006) http://odokon.org/ A taxonomic review of the Japanese Trichogramma (Hymenoptera: Trichogrammatidae) with descriptions of three new species Jeffrey Y. HONDA,1,2,* Laurel TAYLOR,1 Josephine RODRIGUEZ,1,† Naoya YASHIRO3 and Yoshimi HIROSE2,‡ 1 Department of Biological Sciences, San Jose State University; CA 95192–0100, USA 2 Institute of Biological Control, Faculty of Agriculture, Kyushu University; Fukuoka 812–8581, Japan 3 Naruo Senior High School; Nishinomiya 663–8182, Japan (Received 16 August 2005; Accepted 24 December 2005) Abstract Numerous errors and confusion in the literature concerning the genus Trichogramma in Japan have necessitated a for- mal review of this genus. This review corrects and updates Trichogramma host and distribution records from Hokkaido to the Ryukyu Islands, redescribes and designates a lectotype for T. jezoense Ishii, records two Tri- chogramma species new to Japan (T. ostriniae Pang and Chen and T. lingulatum Pang and Chen) and describes three new species (T. yabui Honda and Taylor, T. okinawae Honda, and T. aomoriense Honda). Additionally a key to the species is provided for the 14 known Japanese species as are ITS-2 DNA sequences and SEM micrographs of male genital capsules for the majority of the species to aid biocontrol workers in Trichogramma identification. Key words: Taxonomy; species description; Japanese Trichogramma; DNA sequence; male genital capsule of Trichogramma japonicum Ashmead precluded it INTRODUCTION from being an effective biological control agent Egg parasitoids of the genus Trichogramma (Iyatomi, 1943; Shibuya and Iyatomi, 1950). More Westwood (Hymenoptera: Trichogrammatidae) recent releases of Trichogramma species against parasitize insect pests in over 32 million hectares the diamond back moth, Plutella xylostella (Lin- of agricultural land and forests yearly (Li, 1994), naeus) (Iga, 1987; Miura et al., 2001; Miura, 2003) and have been utilized as biological control agents and the tobacco budworm, Helicoverpa armigera for more than 100 years (Smith, 1996). Of the ap- Hübner (Kakimoto et al., 1998) have been per- proximately 180 species described worldwide, formed, but their use is still being evaluated. Three about 70 species have been employed in biological other species have been apparently imported into control programs concentrating on various crops Japan. Iwasaki et al. (1998) released Trichogramma (corn, rice, wheat, sorghum, sugarcane, sugar beet, evanescens Westwood imported from France for cotton, and soybean); fruits (apple, plum, citrus, the control of Mamestra brassicae (Linnaeus) in avocado, and vineyards); and forest trees (pines sugar beet fields in Hokkaido in 1997, but it is un- and spruce) (Li, 1994; Pinto, 1999). known if these releases became established. In Japan, Trichogramma were first used against Trichogramma ostriniae Pang and Chen was im- the rice stem borer, Chilo suppressalis (Walker), in ported from Taiwan in Japan in 1987 (Hirashima et paddy fields during 1930–1940 with little success. al., 1990), but it was not released in the field In separate field trials, it was concluded that Tri- (Miura, pers. communication). However, Hirai chogramma chilonis Ishii parasitism rates were too (2004) recorded T. ostriniae as an indigenous natu- low for controlling C. suppressalis (Shibuya and ral enemy of Ostrinia furnacalis (Guenée) and Yamashita, 1936), while high superparasitism rates some tortricids from Japan, but this record was *To whom correspondence should be addressed at: E-mail: [email protected] † Present address: Department of Entomology, 320 Morrill Hall, University of Illinois, 505 S. Goodwin Ave., Urbana, IL 61801, USA ‡ Present address: 349 Asano, Munakata 811–3415, Japan DOI: 10.1303/aez.2006.247 247 248 J. Y. HONDA et al. never verified. Test releases using Hirai’s cultured species such as the dorsal lamina were not ade- material was later used for O. furnacalis control in quately described. Minamikawa (1964) later listed corn fields in 1992–93 (Yoshizawa, 1995). Tri- the following Trichogramma species from Japan: chogramma brassicae Bezdenko, another imported Trichogramma australicum Girault, T. chilonis species of Trichogramma, was used in test releases Ishii, T. dendrolimi Matsumura, T. evanescens for the control of M. brassicae in sugar beet fields Westwood, T. japonicum and T. jezoensis Ishii. A in 1997 (Iwasaki et al., 1998) and for the control of seventh Trichogramma species, T. papilionis Na- P. xylostella in greenhouses in 1999 (Miura et al., garkatti, was added to the Japanese fauna (Na- 2001). Again their establishment has not been con- garkatti, 1974). Since this time the status of Japan- firmed. ese Trichogramma taxonomy has changed greatly. Despite the considerable international attention Nagarkatti and Nagaraja (1979) concluded that that Trichogramma has received as an important bi- Asian populations originally identified as T. aus- ological control agent, its taxonomy remains inade- tralicum were actually T. chilonis and were subse- quately understood for a number of reasons. For quently synonymized. Pinto et al. (1982) later des- example, the collection and curation of these ignated a lectotype for T. australicum and stated it minute (approximately 0.5 mm) parasitic wasps has remains known only from Girault’s original mate- proven difficult and greatly slowed the accumula- rial collected in Queensland, Australia. Thus, T. tion of study material (Platner et al., 1999). More- australicum should no longer be considered a over, the early disregard of type specimens has species found in Japan. Questions regarding the caused much confusion in the literature. Because a exact identity of T. evanescens were brought to number of type specimens are lost, unusable, or de- light by Sugonyaev (1986) and Pinto (1999). It scribed inadequately, many species names have may be impossible to accurately assign this name been applied incorrectly and inconsistently in the to a specimen since the holotype of this species is a literature (Pinto et al., 1978; Pinto and Stouthamer, damaged female. Although both Ishii (1941) and 1994; Pinto, 1999). Finally, Trichogramma taxon- Nagarkatti and Nagaraja (1971) recorded T. omy also suffered from an absence of consistent evanescens from Japan, their identifications may be distinguishing morphological characters (Pinto, erroneous as is discussed later in this paper. The 1999). This dilemma was partially resolved by Na- status of T. jezoensis has also been questioned. garkatti and Nagaraja (1971) who discovered the Thought to be lost, we have found Ishii’s original importance of the male genitalia as a diagnostic material and designate a lectotype herein. Finally, taxonomic character. DNA sequences have also four new species recently have been described been proposed as an aid to identification and used from Japan: T. yawarae Hirai and Fursov (1998), T. in a number of studies to characterize Trichogramma kurosuae Taylor, Yashiro, Hirose, and Honda (Tay- species (Pinto et al., 1997; Silva et al., 1999; lor et al., 2005), T. cultellus Jose, and T. umerus Stouthamer et al., 1999). Jose (Jose et al., 2005). The history of Trichogramma taxonomy in Japan This paper represents the first revision of Japan- exemplifies many of the taxonomic difficulties ese Trichogramma. Herein we describe three new prevalent in the genus. For example, Nakagawa species and confirm two Trichogramma species (T. (1900) was the first to record Trichogramma from ostriniae Pang and Chen and T. lingulatum Pang Japan by describing in morphological detail, the and Chen) new to Japan. We provide a species key adult of a Trichogramma species parasitic on eggs for all the known species of Japan, in addition to of the rice stem borer. Although it has been sus- photomicrographs, and diagnostic descriptions of pected that this first description may be of T. japon- male genital capsules for most of the previously icum, it can not be confirmed as none of the origi- described Trichogramma species except for T. nal material exists. Much later, Ishii (1941) was the kurosuae, T. cultellus, and T. umerus that were re- first to produce a key to six Japanese Trichogramma cently covered in detail. Additionally, ITS2-DNA species based on male genitalia; however, it proved sequences that may aid workers in properly identi- little value as it lacked quantitative measures to aid fying Trichogramma have been identified, and we in species discrimination. Moreover, morphologi- document reliable host records that we have veri- cally important characters presently used to define fied through examination of preserved Tri- The Trichogramma of Japan 249 chogramma material including some material from raja (1971): 18–20. Ishii’s original collections. Although the literature Diagnosis. This species appears to be common has recorded many hosts of Trichogramma species in disturbed agricultural settings and is most likely from Japan, most of the host records including to be confused with T. evanescens and T. brassicae. those of Ishii (1941) and Minamikawa (1964) may However, as Pinto (1999) points out, there is much be unreliable as their Trichogramma identifications confusion as to what constitutes either species as may have been inaccurate. some researchers consider them conspecific. To We feel such a treatment is necessary at this time further confuse matters, both Ishii (1941) and not only because many new species are being de- Nagarkatti and Nagaraja (1971) reported that T. scribed in Japan, but also because of the apparent evanescens occurs