Naturwissenschaften (2006) 93:461–465 DOI 10.1007/s00114-006-0132-z

SHORT COMMUNICATION

Iridodial: a powerful attractant for the green lacewing, septempunctata (: )

Qing-He Zhang & Maoling Sheng & Guofa Chen & Jeffrey R. Aldrich & Kamlesh R. Chauhan

Received: 25 January 2006 /Revised: 12 May 2006 /Accepted: 18 May 2006 / Published online: 24 June 2006 # Springer-Verlag 2006

Abstract The lacewing Chrysopa septempunctata Wes- Introduction mael is an important, common predator of several in China, Japan, Russia, and many parts of Europe. Our field The lacewing, Chrysopa septempunctata Wesmael, is an trapping experiments in northeast China showed that males important predator of , mites, and other soft-bodied of this green lacewing are strongly attracted to the lacewing insects in northeast Asia and Europe (Han and Chen 2002). pheromone of Chrysopa oculata Say, (1R,2S,5R,8R)-irido- Green lacewings, especially Chrysopa and Chrysoperla dial. The induced plant volatile, methyl salicylate, was spp., are attracted to various natural products, including unattractive to C. septempunctata by itself at the concen- host-plant (Flint et al. 1979; Hooper et al. 2002; Pai et al. tration tested, but synergistic when combined with iridodial 2004; Suda and Cunningham 1970; Zhu et al. 1999, 2005) where the lacewing population was high. (1R,4aS,7S,7aR)- and herbivore-induced volatiles such as methyl salicylate Nepetalactol and (4aS,7S,7aR)-nepetalactone ( sex (James 2003a,b, 2006; James and Price 2004), as well pheromone components) caught significantly more males as sex pheromone components of aphids [i.e., of C. septempunctata than did blank control traps, but were (1R,4aS,7S,7aR)-nepetalactol and (4aS,7S,7aR)-nepetalac- inferior to iridodial dispensers, which remained strongly tone] (Boo et al. 1998, 2003; Hooper et al. 2002). Recently, attractive to C. septempunctata males for at least Zhang et al. identified a male-produced aggregation 2.5 months. These results indicate that (1R,2S,5R,8R)- pheromone from Chrysopa oculata Say (Zhang et al. iridodial is a powerful attractant for C. septempunctata, 2004) and Chrysopa nigricornis Burmeister (Zhang et al. and may have great potential for enhanced biological 2006). The synthetic pheromone, (1R,2S,5R,8R)-iridodial control of garden, agricultural, and forest pests. (Chauhan et al. 2004), is superior to all other reported attractants for green lacewings in the genus Chrysopa (Zhang et al. 2004). Our goal in this study was to determine the attractiveness Q.-H. Zhang (*) of (1R,2S,5R,8R)-iridodial, methyl salicylate, Sterling International, Inc., (1R,4aS,7S,7aR)-nepetalactol, (4aS,7S,7aR)-nepetalactone, 3808 N. Sullivan Rd, Bldg 16BV, and 2-phenylethanol to C. septempunctata in China. Spokane, WA 99216-1616, USA e-mail: [email protected] : M. Sheng G. Chen Materials and methods General Station of Forest Pest Management, State Forestry Administration, No. 58, Huanghe North Street, Experiments were conducted from June through August of Shengyang 110034, People’s Republic of China 2005 at two locations in northeast China. Traps (Pherocon : VI; Trécé, Adair, Oklahoma, USA) were hung 1.5–2.0 m J. R. Aldrich K. R. Chauhan above the ground on trees about 10 m apart, with ≥ 20 m USDA-ARS Chemicals Affecting Insect Behavior Laboratory, – B-007, BARC-West, between trap lines (sets). Traps (2 3 sets/location), ran- Beltsville, MD 20705, USA domized within a set, were rotated in each set once a 462 Naturwissenschaften (2006) 93:461–465 week (Byers 1991) so that traps appeared at least once per tata males were captured from June 15 through July 20, location. 2005. Traps baited with IRI alone or combined with MS Experiment 1 was conducted at two locations with two caught significantly more C. septempunctata males than did sets of traps at each location to test (1R,2S,5R,8R)-iridodial blank control traps, while MS alone was inactive [Fig. 1b; [IRI, 80%; with ∼20% of (1R,2S,5R,8S)-iridodial as an F=54.44, n=10, P<0.001, ANOVA on log (x+1) trans- impurity; 5 mg in 50 μl of hexane with 1% BHT applied to formed data, followed by REGW multiple-Q test at felt in a 20×50 mm 6-mil polyethylene (PE) bag; release α=0.05]. Addition of MS to IRI had no effect (Fig. 1b). rate not determined, but ≥50% of IRI still left in the In experiment 2, 1,762 C. septempunctata males were dispenser after 2 months exposure in the lab hood at ca. captured from July 12 through August 25, 2005. IRI, 20°C according the GC-MS analysis of the extracted (1R,4aS,7S,7aR)-nepetalactol, and (4aS,7S,7aR)-nepetalac- dispensers], methyl salicylate (MS: 99%, Aldrich Chemical; tone were all attractive to males of C. septempunctata, 1.5 g/PE bag; ca. 50 mg/day release) (James 2003a, 2006; while 2-phenylethanol was inactive [Fig. 3; F=91.47, n=18, James and Price 2004), and IRI+MS in a PE-bag. Location P<0.0001, ANOVA on log (x+1) transformed data, fol- 1 was a mixed stand of Padus racemosa Schneid. and lowed by REGW multiple-Q test at α=0.05]. Traps baited Pinus tabulaeformis Carr., Beiling Park, Shenyang, China; with IRI caught significantly more C. septempunctata than location 2 was a forest of Larix gmelinii (Rupr.) Rupr. and did the traps baited with either nepetalactol or nepetalac- Betula platyphylla Sukachev., Daxinggou, Jilin (900 km tone, and the former was significantly more attractive than northeast of location 1). the latter compound (Fig. 3). Experiment 2, including three trap sets (50 m from location 1, exp. 1), tested IRI plus three other reported kairomone attractants: (1R,4aS,7S,7aR)-nepetalactol (90% with ∼2% impurity of iridodial), (4aS,7S,7aR)-nepetalac- Discussion tone (98%) (Zhang et al. 2004), and 2-phenylethanol (99%; Aldrich Chemical). Five milligram of IRI, nepetalactol or (1R,2S,5R,8R)-Iridodial is a powerful attractant for nepetalactone (each in 50 μl of hexane with 1% BHT) were C. septempunctata males in northeast China. Golden-eyed loaded in separate PE-bags as above; 2-phenylethanol (2 g) lacewing (C. oculata) males evidently produce pheromone was loaded in a 3-mil, 40×50-mm PE-bag (release rate of in elliptical glands abundantly distributed on the 3rd–8th 5 mg/day). abdominal sternites (Zhang et al. 2004), whereas in C. nigricornis, the pheromone likely comes from thoracic glands in males (Zhang et al. 2006). Further tests at Results Beltsville, Maryland showed that iridodial does, in fact, attract C. oculata females (Chauhan et al., unpublished No female green lacewings were captured in either data). However, unlike males, the females do not approach experiment. In experiment 1, location 1, a total of 2822 close enough to be caught in traps, possibly because they C. septempunctata males were caught from June 7 through call males acoustically at close range or need the male- August 30, 2005. Traps baited with IRI alone or combined produced species-specific acoustical signals for close range with MS caught significantly more C. septempunctata communication (Henry 1982). (1R,2S,5R,8R)-Iridodial also males than did control traps, while MS alone was inactive attracted males of Chrysopa quadripunctata (Zhang et al. (Fig. 1a; F=334.8, n=22, P<0.0001, ANOVA on log (x+1) 2004) and Chrysopa coloradensis (Zhang et al. 2006), transformed data, followed by REGW multiple-Q test at although it is not certain that these species or C. septempunc- α=0.05). Addition of MS to IRI showed a synergistic effect tata actually produce (1R,2S,5R,8R)-iridodial; chemical at location 1 (Fig. 1a). In addition to lacewings, a total of analyses are needed for these species. However, as with 41 hoverflies (Diptera: Syrphidae; common predators of C. oculata, there are >10,000 elliptical glands on the aphids) were captured during the first 3 weeks in traps abdomen of C. septempunctata males (Principi 1949). baited with IRI alone (18), MS alone (11), and their binary Similar abdominal glands occur in males of Chrysopa blend (12), while control traps caught none [F=2.61, n=6, virdana Schneider (Principi 1954a) and Chrysopa perla P=0.08, ANOVA on log (x+1) transformed data, followed (L.) (Principi 1954b), and on the thorax of Pseudomallda by REGW multiple-Q test at α=0.05]. Two flight peaks of flavifrons (Brauer) and Pseudomallda ventralis (Curtis) C. septempunctata males were detected at this location (Principi 1954b). Sex-specific epidermal glands are appar- during the trapping period (Fig. 2), indicating there might ently absent from Chrysoperla lacewings, such as Chryso- be two generations per year in this region. Dispensers of perla rufilabris (Brumeister) (Zhang et al. 2004)and IRI and IRI + MS remained strongly attractive after Chrysoperla plorabunda (Fitch) (Zhang et al. 2006), and 2.5 months in the field. At location 2, 235 C. septempunc- individuals of these species are not attracted to iridodial. Naturwissenschaften (2006) 93:461–465 463

Fig. 1 Captures of male 7 6 (S) CHO Chrysopa septempunctata in 2 (R) 100 1 C traps baited with (1R,2S,5R,8R)- 3 A 5 CHO iridodial (IRI), methyl salicylate 4 (R) 8 (R) (MS), and their binary blend. 80 a Location 1: Beiling Park, B Shenyang, China, N=22, June 60 7–August 30, 2005; b Location 2: Daxinggou, Jilin, China, O N=10, June 15–July 20, 2005. 40 Bars with different letters are OCH3 significantly different (P<0.05), ANOVA on log (x+1) trans- 20 OH formed data, followed by A A REGW multiple-Q test 0 20 B B 16 B

Lacewings/trap/week +SE 12

8

4 A A 0 Blank Iridodial Methyl salicylate IRI+MS (IRI) (MS)

Methyl salicylate is reportedly an attractant for both numbers were low. C. oculata (Zhang et al. 2004) and sexes of C. nigricornis and C. oculata (James 2003a, 2006) C. nigricornis (Zhang et al. 2006) were also variable in along with several other beneficial insects (James and Price response to methyl salicylate or to its binary blend with 2004; Zhu and Park 2005). However, in the current study (1R,2S,5R,8R)-iridodial. The disparity between the activi- methyl salicylate was unattractive by itself to C. septem- ties of methyl salicylate among various studies might be punctata at the concentration tested (ca. 50 mg/day release), due to differences in its release rate or presence/absence of but showed a synergistic effect at location 1 when the powerful pheromone component, iridodial, or both. combined with iridodial where the lacewing population 2-Phenylethanol is a common plant volatile that is reportedly was high, but had no effect at location 2 where lacewing a kairomonal attractant for C. carnea (Say) (whose adults

140

120 IRI MS IR+MS 100

80

60

40 Lacewings/trap/week

20

0

4 1 8 2 9 3 0 /1 /2 /2 /5 1 /1 /2 /9 2 /3 6 6 6 7 7/ 7 7/26 8 8 8/16 8/ 8 Date Fig. 2 Weekly captures of male Chrysopa septempunctata in traps baited with (1R,2S,5R,8R)-iridodial (IRI), methyl salicylate (MS), and their binary blend at location 1 (data taken from experiment 1, location 1) 464 Naturwissenschaften (2006) 93:461–465

7 6 (S) CHO 2 (R) 1 3 5 OH 4 (R) 8 CHO D (R) 7 1 60 7a 2 O 6 4a 3 5 4 50 O C

40 1 7 7a 2 O 6 4a 3 30 5 4

B 20 OH

10 Lacewings/trap/week +SE A A 0 Blank Iridodial Nepetalactone Nepetalactol 2-Phenylethanol Fig. 3 Captures of male Chrysopa septempunctata in traps baited with Shenyang, China, N=18, July 12–August 25, 2005. Bars with different the lacewing pheromone, (1R,2S,5R,8R)-iridodial, and three other letters are significantly different (P<0.05), ANOVA on log (x+1) reported kairomonal attractants: (1R,4aS,7S,7aR)-nepetalactol, transformed data, followed by REGW multiple-Q test (4aS,7S,7aR)-nepetalactone and 2-phenylethanol, at Beiling Park, feed on flowers) (Zhu et al. 1999, 2005), but was aphid sex pheromones and structurally similar compounds unattractive to Chrysopa spp. (whose adults are carnivo- is unclear. Hooper et al. (2002) challenged an earlier rous) (Zhang et al. 2006). hypothesis that Chrysopa species are attracted to aphid (1R,4aS,7S,7aR)-Nepetalactol and (4aS,7S,7aR)-nepeta- sex pheromones to seek aphids for food based on the fact lactone are sex pheromone components for many aphids that the seasonal and diel timing of aphid pheromone (Birkett and Pickett 2003) and were found to be attractive release does not match the timing of lacewing adult feeding to several Chrysopa spp., including Chrysopa congnata [see also Boo et al. (2003) for details]. Our discoveries of (McLachlan), Chrysopa formosa (Brauer) and Chrysopa C. oculata (Zhang et al. 2004)andC. nigricornis (Zhang et phyllochroma (Wesmael) (Boo et al. 2003; Hooper et al. al. 2006) pheromones support their challenge to the 2002), C. oculata (Zhang et al. 2004; Zhu et al. 2005), and kairomonal role of the aphid sex pheromone components. C. nigricornis (Zhang et al. 2006); the lactol was more Instead, we suggest that the attraction of lacewings to aphid attractive than the lactone. In our study, these two pheromone components may be due to their structural compounds significantly attracted C. septempunctata similarity to the lacewing pheromone, (1R,2S,5R,8R)- males, the former again being more attractive than the iridodial, and to the inevitable presence of iridodial isomers latter. The significant attraction of the green lacewing males as impurities of (1R,4aS,7S,7aR)-nepetalactol (Zhang et al. to (1R,4aS,7S,7aR)-nepetalactol might be due to attraction 2004). to the lactol itself or to an ∼2% impurity of (1R,2S,5R,8R)- In the current study, the PE-bag dispensers loaded with iridodial in the synthetic lactol (Chauhan et al. 2004), or iridodial or iridodial plus methyl salicylate remained strongly both. attractive to C. septempunctata for at least 2.5 months during Several other natural products are reportedly attractive to the summer. Moreover, (1R,2S,5R,8R)-iridodial, methyl sa- lacewings, among which methyl eugenol attracts both licylate, or their combination also attract many other Chrysopa basalis Walker (Suda and Cunningham 1970) beneficial insects, such as hoverflies, lady beetles, and and Ankylopteryx exquisite (Nakahara) (Pai et al. 2004). predatory bugs (James and Price 2004; Zhang et al. 2006; Dihydronepetalactol isomers (neomatatabiol and isomatata- and this paper). A pheromone-based lacewing attractant is biol) isolated from a Japanese vine (Actinidia polygama now being developed at Sterling International, for manipu- Miq) were attractive to males of C. septempunctata and lating natural or artificially augmented populations of lace- Chrysopa japana Okomoto (Hyeon et al. 1968; Sakan et al. wings and other beneficial insects for enhanced biological 1970). These compounds are stereochemically similar to control of garden, agricultural, and forest insect pests. (1R,4aS,7S,7aR)-nepetalactol, and the synthetics attracted males of C. congnata in Korea, and Nineta vittata Acknowledgements We thank D. Hoover, K. Young, D. O. (Wesmael) and Peyerimhoffina grancilis in the UK (Hooper Welshons, and A. Margaryan for lab assistance and Rod Schneidmiller, et al. 2002). The rationale behind attraction of chrysopids to the president of Sterling International, for general support. Naturwissenschaften (2006) 93:461–465 465

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