Journal of Insect Science: Vol. 13 | Article 94 Shrestha and Enkegaard The green lacewing, Chrysoperla carnea: Preference between lettuce aphids, Nasonovia ribisnigri, and western flower thrips, Frankliniella occidentalis Govinda Shresthaa and Annie Enkegaardb Department of Agroecology, Science and Technology, Aarhus University, Research Centre Flakkebjerg, Forsøgsvej 1, DK-4200 Slagelse, Denmark Downloaded from Abstract This study investigated the prey preference of 3rd instar green lacewing, Chrysoperla carnea Stephens (Neuroptera: Chrysopidae), between western flower thrips, Frankliniella occidentalis http://jinsectscience.oxfordjournals.org/ (Pergande) (Thysanoptera: Thripidae), and lettuce aphids, Nasonovia ribisnigri (Mosley) (Hemiptera: Aphididae) in laboratory experiments at 25 ± 1º C and 70 ± 5% RH with five prey ratios (10 aphids:80 thrips, 25 aphids:65 thrips, 45 aphids:45 thrips, 65 aphids:25 thrips, and 80 aphids:10 thrips). Third instar C. carnea larvae readily preyed upon both thrips and aphids, with thrips mortality varying between 40 and 90%, and aphid mortality between 52 and 98%. Chrysoperla carnea had a significant preference for N. ribisnigri at two ratios (10 aphids:80 thrips, 65 aphids:25 thrips), but no preference for either prey at the other ratios. There was no by guest on November 16, 2015 significant linear relationship between preference index and prey ratio, but a significant intercept of the linear regression indicated an overall preference of C. carnea for aphids with a value of 0.651 ± 0.054. The possible implications of these findings for control of N. ribisnigri and F. occidentalis by C. carnea are discussed. Keywords: Aphididae, biological control, Chrysopidae, prey ratios, Thripidae Correspondence: a [email protected], b [email protected] Editor: Tugrul Giray was editor of this paper. Received: 14 February 2012 Accepted: 15 March 2013 Published 30 September 2013 Copyright: This is an open access paper. We use the Creative Commons Attribution 3.0 license that permits unrestricted use, pro- vided that the paper is properly attributed. ISSN: 1536-2442 | Vol. 13, Number 94 Cite this paper as: Shrestha G, Enkegaard A. 2013. The green lacewing, Chrysoperla carnea: Preference between lettuce aphids, Nasonovia ribisnigri, and western flower thrips, Frankliniella occidentalis. Journal of Insect Science 13:94. Available online: http://www.insectscience.org/13.94 Journal of Insect Science | http://www.insectscience.org 1 Journal of Insect Science: Vol. 13 | Article 94 Shrestha and Enkegaard Introduction Chrysoperla carnea occurs naturally in a wide range of agroecosystems and is commercially The western flower thrips, Frankliniella occi- available in Europe and North America dentalis (Pergande) (Thysanoptera: (Wang and Nordlund 1994; Tauber et al. Thripidae), and the lettuce aphid, Nasonovia 2000). It has primarily been used through ribisnigri (Mosley) (Hemiptera: Aphididae), augmentative release to control various aphid are two economically important pests of let- species in greenhouses and outdoor crops tuce (Blackman and Eastop 1984; Palumbo (Scopes 1969; Tulisalo and Tuovinen 1975; 1998; Natwick et al. 2007). Both pests are Turquet et al. 2009). However, this species is categorized as r-selected species with high a generalist predator, and is also known to reproductive capacity, parthenogenesis, and predate on other soft-bodied arthropods, in- short generation time (Mound and Teulon cluding scale insects, leafhoppers, whiteflies, 1995; Tatchell 2000; Diaz et al. 2010). Frank- psyllids, thrips, lepidopterans, and mites liniella occidentalis damages lettuce plants by (Principi and Canard 1984). In field studies, Downloaded from scarring edible leaves and causing rib discol- satisfactory results were reported for C. car- oration, while N. ribisnigri causes leaf nea control of citrus thrips, Scirtothrips citri distortion and reduces seedling vigor (Pa- (Khan and Morse 1999a), leafhoppers, Ery- lumbo 1998). Their cryptic feeding and ability throneura variabillis (Daane et al. 1996), and http://jinsectscience.oxfordjournals.org/ to act as major vectors for viral diseases are tobacco budworms, Heliothis virescens other negative attributes of these pests (Ridgway and Jones 1968). (Blackman and Eastop 1984; Yudin et al. 1987; Yudin et al. 1988). Finally, both pests The predation capacity of C. carnea towards are considered cosmetic pests (Palumbo 2000; the lettuce aphid has recently been examined Kift et al. 2004) because their presence in har- (Shrestha 2011), but no information is availa- vested products reduces the market value of ble about the prey preferences of C. carnea the products. towards N. ribisnigri and F. occidentalis, by guest on November 16, 2015 which appear simultaneously in lettuce fields. The feeding preferences of N. ribisnigri for The prey preference of a predator directly af- heart leaves and the cryptic behavior of F. oc- fects the control efficiency of its various prey cidentalis make them difficult to control with (Xu and Enkegaard 2009); thus, knowledge on insecticides (Seaton et al. 1997; Parker et al. preference is important to determine the po- 2002; Stufkens and Teulon 2003). Using bio- tential of predators in situations in which logical control would be an alternative control several pest species are present in the crop of strategy for these pests. Several beneficial interest (Enkegaard et al. 2001). Consequent- species have been studied for their potential to ly, the primary objective of this study was to control either aphids or thrips, and many are evaluate the prey preference of C. carnea be- commercially available and applied in practice tween N. ribisnigri and F. occidentalis. (Powell and Pell 2007; Cloyd 2009). Among the more polyphagous species that might have Materials and Methods a potential for contributing to control of both aphids and thrips is the green lacewing, Plants and insects Chrysoperla carnea Stephens (Neuroptera: Iceberg lettuce, Lactuca sativa L. (Asterales: Chrysopidae). Asteraceae) var. ‘Mirette RZ’ was grown in plastic pots filled with a mix of perlite and Journal of Insect Science | http://www.insectscience.org 2 Journal of Insect Science: Vol. 13 | Article 94 Shrestha and Enkegaard vermiculite and maintained in a controlled cm diameter) lined with a thin layer of solidi- environment glasshouse (15–20º C, 55–70% fied agar solution (10%). The edge of the leaf RH, 16:8 L:D) at Research Centre disc was sealed with agar to prevent thrips Flakkebjerg, Aarhus University, Denmark. larvae and aphid nymphs from hiding beneath the leaf. N. ribisnigri nymphs (3rd and 4th im- Nasonovia ribisnigri and F. occidentalis were mature stages) and F. occidentalis larvae (1st reared separately on plants of lettuce and and 2nd instars) were gently transferred with a bean, Phaseolus vulgaris L. (Fabales: Fabace- fine camel hair brush from the rearings to the ae) var. “Montano”, respectively, in nylon net Petri dish. Aphid nymphs were introduced cages (68 × 75 × 82 cm) and maintained in a first and allowed to settle for 0.5–1 hr prior to controlled environment glasshouse compart- introduction of thrips larvae to the dish. Sub- ment (20 ± 1º C or 25 ± 1º C, respectively, sequently, one starved C. carnea larva was 16:8 L:D, 55–70% RH). Nasonovia ribisnigri placed in a Petri dish, which was then sealed was originally supplied from Dr. Beatriz M. with parafilm. The Petri dishes were placed in Downloaded from Diaz (Department of Plant Protection, a plexiglass box (30.5 × 22.0 × 5.5 cm), the CCMA-CSIC, Madrid, Spain). Frankliniella bottom of which was covered with a saturated occidentalis had been reared at Research Cen- salt water solution to maintain70 ± 5% RH. tre Flakkebjerg, Aarhus University, Denmark, The experiment was carried out in a climate http://jinsectscience.oxfordjournals.org/ for 10 years. cabinet at 25 ± 1º C, 70 ± 5% RH, and 3 hr light conditions. After 3 hr, the numbers of One- to two-day-old 2nd instar C. carnea lar- live aphid nymphs and thrips larvae were vae as well as eggs of the flour moth, Ephestia counted under a stereomicroscope. Based on a kuehniella Zeller (Lepidoptera: Pyralidae), preliminary experiment five prey ratios (10 were obtained from EWH Bio Production aphids:80 thrips, 25 aphids:65 thrips, 45 (www.bioproduction.dk). The C. carnea lar- aphids:45 thrips, 65 aphids:25 thrips and 80 rd vae were reared individually to the 3 instar aphids:10 thrips) were selected, and each was by guest on November 16, 2015 on E. kuehniella eggs in Petri dishes (diame- tested in 10–15 replicates. Control treatments ter: 5.5 cm) in a climate cabinet at 25 ± 1° C, without C. carnea (8–10 replicates/ratio) were 70 ± 5% RH, and 16:8 L:D. The larvae were also carried out. transferred to new Petri dishes with an excess of E. kuehniella eggs at two-day intervals. The Data analysis 3rd instar larval stage was ascertained on the After correction of the observed mortalities basis of morphology and developmental time with the respective control mortality (Abbott (Scopes 1969; Butler and Ritchie 1970; 1925), Manly’s preference index (Manly Tauber 1974; Gepp 1984). One day before the 1974) was calculated for each ratio of offered experiment, 3rd instar larvae were starved for prey: 24 hr by keeping them individually in Petri ⎛ e1 + 0.001⎞ dishes in a climate cabinet at the same condi- log⎜ ⎟ ⎝ A1 ⎠ tions as above. β 1 = ⎛ e1 + 0.001⎞ ⎛ e2 + 0.001⎞ log⎜ ⎟ + log⎜ ⎟ Prey preference experiment ⎝ A1 ⎠ ⎝ A2 ⎠ A circular lettuce leaf disc (diameter: 5 cm) was placed at the bottom of a Petri dish (8.5 Journal of Insect Science | http://www.insectscience.org 3 Journal of Insect Science: Vol. 13 | Article 94 Shrestha and Enkegaard Table 1. Mean mortality (± SE) inflicted by 3rd instar larvae of Chrysoperla carnea on nymphs of Nasonovia ribisnigri and larvae of Frankliniel- la occidentalis when offered at different ratios, as well as the corresponding preferences indices (β) (± SE). Means followed by a different letter in the same column are significantly different (Tukey test; p = 0.05). Results The predation rates of C. carnea on the two prey species is shown in Figure 1.