RAPID COMMUNICATION Female Goldeneyed Lacewings (Neuroptera: Chrysopidae) Approach but Seldom Enter Traps Baited with the Male-Produced Compound Iridodial 1,2 1 3 1 KAMLESH R. CHAUHAN, VICTOR LEVI, QING-HE ZHANG, AND JEFFREY R. ALDRICH J. Econ. Entomol. 100(6): 1751Ð1755 (2007) ABSTRACT Earlier, we identiÞed (1R,2S,5R,8R)-iridodial as a male-speciÞc compound of the goldeneyed lacewing, Chrysopa oculata Say (Neuroptera: Chrysopidae), but traps baited with this compound caught almost exclusively males. In the present report, we demonstrated by sweep-net sampling and observation in the vicinity of pheromone lures that C. oculata females, and males, are strongly attracted to iridodial. Aggregation activity of C. oculata adults occurred between dusk and dawn. This research demonstrates that iridodial may be useful to induce goldeneyed lacewings to lay eggs in targeted plant patches for biological pest control. KEY WORDS aphids, biocontrol, goldeneyed lacewing, aggregation pheromone In 2004, we identiÞed (1R,2S,5R,8R)-iridodial from iments in 2004 and 2005 to monitor the responses of males of the goldeneyed lacewing, Chrysopa oculata goldeneyed lacewing females to the male-produced Say (Neuroptera: Chrysopidae), and we showed that compound (1R,2S,5R,8R)-iridodial and to its diaste- the synthetic compound (Chauhan et al. 2004; Zhang reomer (1R,2S,5R,8S)-iridodial. et al. 2004) strongly attracted conspeciÞc males in the Þeld. This discovery indicated that the attraction of Materials and Methods lacewings in the genus Chrysopa to the aphid phero- mone components Z,E-nepetalactol and Z,E-nepeta- Three Þeld experiments were carried out from early lactone (Boo et al. 1998, 2003; Hooper et al. 2002) may May through early September of 2004 at two locations be due to impurities of iridodial in synthetic aphid on the Beltsville Agricultural Research Center pheromone formulations. However, in our earlier (BARC), Beltsville, MD, and a follow-up experiment studies on C. oculata and other Chrysopa species was conducted in 2005 from June to August. Isomeric (Zhang et al. 2006a, 2006b), we failed to demonstrate iridodials (Fig. 1) were synthesized as described by attraction of Chrysopa females to iridodial, calling into Chauhan et al. (2004): (1R,2S,5R,8R)-iridodial (IRI-R; question the role of this lacewing semiochemical. 92% with Ϸ8% of 8S isomer), the C. oculata male- Various green lacewings are attracted to host plant produced compound; and the unnatural, but anten- volatiles (Suda and Cunningham 1970, Flint et al. 1979, nally active diastereomer (1R,2S,5R,8S)-iridodial Zhu et al. 1999, Hooper et al. 2002, Pai et al. 2004, Zhu (IRI-S; 88% with Ϸ12% of 8R isomer). Lures were et al. 2005), particularly methyl salicylate (James prepared by applying 5 mg of iridodial per 50 ␮lof 2003a, 2003b; James and Price 2004; James 2006). How- heptane to the well of gray rubber septa (5-mm sleeve- ever, synthetic iridodial is a much more powerful type, The West Co., Lititz, PA). attractant for males of Chrysopa species (Zhang et al. An initial survey experiment was carried out in a 2004, 2006a, 2006b) than are plant-produced attract- meadow at BARC-East and a soybean, Glycine max ants (but see Hyeon et al. 1968). For practical utility, (L.) Merr., Þeld on the BARC North Farm from 9 to and to fully appreciate the complex acoustic and 31 May 2004 to determine which site had the highest pheromonal communication system of green lacew- lacewing population for future experiments. Two pairs ings in general, it is essential to know whether and how of Jackson Delta traps with sticky inserts (Agrisense, Chrysopa females respond to volatiles released by con- Fresno, CA) baited with either lacewing pheromone speciÞc males. Therefore, we conducted Þeld exper- lures or the solvent control septa were deployed at each site. Traps were hung about Ϸ1 m above the Mention of commercial products does not constitute an endorse- ground on metal stakes, Ϸ10 m apart between the ment by USDA. treatment and control traps within a pair, and Ϸ15 m 1 USDAÐARS Invasive Insects Biocontrol & Behavior Laboratory, between sets of pairs. Pheromone lures and sticky B-007, BARC-West, Beltsville, MD 20705. inserts were refreshed, and their trap positions within 2 Corresponding author, e-mail: [email protected]. 3 Sterling International Inc. 3808 N. Sullivan Road, Building 16BV, the pairs were shifted every week. Based on this pilot Spokane, WA 99216. survey, subsequent experiments were carried out in 1752 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 100, no. 6 50 A ally around traps. Eight pairs of pheromone or blank 45 rubber septa dispensers were deployed on metal SE Males; Σ=1227; N=24 ± 40 Females; Σ=28; N=24 stakes for the sweep netting experiment, but instead of sampling with a net, the soybean plants in a 5-m radius 35 around the dispensers were gently shaken using a CHO 30 CHO yardstick in the early morning. The numbers and sex / trap week 25 CHO CHO of the lacewings that ßew were counted and identi- 20 Þed. A lacewing was identiÞed as female if its abdomen IRI-R IRI-S 15 was swollen upon observation after it landed. Lacew- C. oculata ings that ßew far away or were not found after they 10 # of B alighted could not be determined, and they were only 5 a bbC counted. 0 Due to heterogeneity of variances among treat- IRI-R IRI-S Blank ments, trap catch data were analyzed using the non- Fig. 1. Captures of C. oculata adults in traps baited with parametric KruskalÐWallis analysis of variance the lacewing pheromone IRI-R, its unnatural isomer IRI-S, or (ANOVA) on rank test, followed by the StudentÐ solvent only (14 JuneÐ6 August 2004, Beltsville, MD). Bars NewmanÐKuels all pairwise comparison to separate with the same letter for each sex are not signiÞcantly differ- means (Zar 1984). Data from the net sweeping and ent (P Ͼ 0.05) by KruskalÐWallis ANOVA on ranks, followed by the StudentÐNewmanÐKeuls all pairwise comparison. visual check experiments were analyzed by paired t-tests at ␣ ϭ 0.05 level. soybean Þelds on the BARC North Farm. No herbicide Results or pesticide treatments were applied in these Þelds. For the test comparing isomeric iridodials, trans- In the initial survey experiment, 132 C. oculata males parent bucket traps (Aldrich et al. 1984) with lures in total were caught in sticky traps, but no females placed in the bottom of traps were deployed from 11 were captured during this entire test. The number of June to 6 August 2004. This experiment consisted of C. oculata males per visit per trap baited with IRI-R four sets of traps (a set is one line of three traps) hung (mean Ϯ SE ϭ 7.69 Ϯ 0.94; N ϭ 16) was signiÞcantly Ϸ15 m apart from stakes as described above, with Ϸ30 greater than that for the blank control traps (mean Ϯ m between trap lines. Initially, the positions of treat- SE ϭ 0.56 Ϯ 0.16; N ϭ 16). More than twice as many ments within a set of traps were allocated randomly, goldeneyed lacewings were captured at the BARC and then the treatments (IRI-R, IRI-S, and blank) North Farm soybean Þeld (⌺ϭ91) than the BARC- were systematically rotated among trap positions East meadow (⌺ϭ41); therefore, future experiments within a set after each replicate so that treatments were conducted at the BARC North Farm. were placed at least once per location (Latin-square In total, 1,227 C. oculata males and 28 females were design; Byers 1991). The traps were visited on every captured during the experiment comparing isomeric Monday, Wednesday, and Friday during the testing iridodials. Traps baited with the synthetic lacewing period; thus, each replicate lasted 2Ð3 d. Captured pheromone IRI-R captured signiÞcantly more males lacewings were taken to the laboratory for species and and females of C. oculata adults than did the traps gender determination, and counting. Dispensers were treated with the unnatural enantiomer IRI-S or blank refreshed every second week. control traps (Fig. 1). The IRI-SÐbaited traps also In experiments run from 10 July to 9 September 2004 caught signiÞcantly more males than did the control and 11 June to 26 August 2005, lacewings in the vicinity traps, but the number of females caught was not sig- of heptane-treated control and IRI-R pheromone dis- niÞcant from that for control traps (Fig. 1). The num- pensers (rubber septa inserted in open 1-ml plastic ber of females caught in traps baited with IRI-R was centrifuge vials) were monitored by sweep netting 40 times less than that of the males, but it was still around dispensers in soybean Þelds. Four pairs of signiÞcantly greater than the number of females IRI-R pheromone and heptane control dispensers caught in IRI-SÐbaited or blank control traps (Fig. 1). were hung from metal stakes as described above, with Also, four males of Chrysopa quadripunctata Burmeis- Ϸ20 m between dispenser pairs and Ϸ30 m between ter were captured in traps baited with IRI-R, and three sets of pairs. Sweep samples (Ϸ10 sweeps) were col- male and one female Chrysoperla rufilabris (Burmeis- lected twice per week between 6:00 and 8:00 a.m. in a ter) were caught in control traps. 5-m radius around the stakes baited with either pher- Impressive numbers of female lacewings were cap- omone lures or blank controls. The positions of pher- tured by sweep netting around pheromone-treated omone lure and blank control within a pair were dispensers. In the 2004 experiment, in total 661 males shifted after each sampling, and captured lacewings and 226 females of C.