EUROPEAN JOURNAL OF ENTOMOLOGYENTOMOLOGY ISSN (online): 1802-8829 Eur. J. Entomol. 115: 364–371, 2018 http://www.eje.cz doi: 10.14411/eje.2018.036 ORIGINAL ARTICLE Flora surrounding rice fi elds as a source of alternative prey for coccinellids feeding on the pests of rice CHITRA SHANKER 1, LYDIA CHINTAGUNTA 1, SAMPATHKUMAR MUTHUSAMY 2, SUNIL VAILLA 1, AMUDHAN SRINIVASAN 1 and GURURAJ KATTI 1 1 ICAR – Indian Institute of Rice Research, Rajendranagar, Hyderabad 500030, Telangana, India; e-mails: [email protected], [email protected], [email protected], [email protected], [email protected] 2 ICAR – National Bureau of Agricultural Insect Resources, Bengaluru 560024, Karnataka, India; e-mail: [email protected] Key words. Coleoptera, Coccinellidae, conservation, biological control, generalist predators, gut-content analysis, prey spectrum, planthoppers, aphids, rice Abstract. Coccinellids are effective predators and a key component of the predator guild in rice ecosystems. In order to enhance their effi cacy, a study was undertaken to assess the seasonal movement of coccinellids into rice fi elds and the role of the sur- rounding fl ora on their colonization. The seasonal abundance of coccinellids and their prey was recorded on the rice crop and the surrounding fl ora at fortnightly intervals from 2012 to 2015. Coccinellid prey range was assessed using PAGE electrophoresis. The herbivorous insects associated with weeds were Aphis gossypii Glover, Aphis craccivora (Koch), Cicadulina bipunctata (Meli- char), Schizaphis graminum (Rondani), Sitobion sp., Thaia oryzivora Ghauri and Zygina maculifrons Matsumura. Of the species of coccinellids recorded in rice fi elds, Harmonia octomaculata (Fabricius), Micraspis discolor (F.), Propylea dissecta (Mulsant), Coccinella transversalis Fabricius, Cheilomenes sexmaculata (Fabricius), Scymnus nubilus Mulsant and Brumoides suturalis (Fabricius) were also recorded on weeds. The esterase profi les indicated that the leafhoppers and aphids on the weeds were the prey of the coccinellids before they colonized the rice fi elds. The coccinellids recorded on the weeds showed bands correspond- ing to the insects present on the weeds. Beetles collected from rice fi elds had different bands, some of which corresponded to the green leafhopper (GLH) Nephotettix virescens Distant, the brown planthopper (BPH) Nilaparvata lugens Stal and white backed planthopper (WBPH) Sogatella furcifera Hovarth infesting rice. In addition, some bands corresponded to hoppers and aphids that were present on the surrounding fl ora. The results indicate the importance of surrounding fl ora in the conservation and coloniza- tion of rice fi elds by coccinellids. INTRODUCTION enhance natural control and prevent pest outbreaks. Con- Generalist predators play an important role in regulat- servation of native natural enemies also reduces pesticide ing insect pests in agricultural ecosystems (Joon & Seung, use and their detrimental effects on the environment (Bo- 2001). Although their ecological role in pest management reau de Roincé et al., 2012). Among generalist predators, was underestimated in the past, recently, the importance some species of coccinellids are widely reported occurring of generalist predators has been reconsidered (Symondson in rice fi elds, where they mostly feed on aphids (Rekha et et al., 2002). In particular, the development of molecular al., 2009; Shanker et al., 2013a). techniques for detecting the presence of prey in the guts Many weeds are also known to harbour coccinellids of the predators has enhanced our understanding of the (Schmid, 1992; Kranz et al., 2002) on which they ovi- trophic links in agricultural ecosystems (Pompanon et al., posit and feed on pollen/nectar and alternate prey. Some 2012). By manipulating the abundance and assemblage of plants, in particular those belonging to the aromatic fam- generalist predators it is possible to signifi cantly affect the ily Apiaceae, are more attractive than others (Schaller & abundance of pests (Symondson et al., 2002). For example, Nentwig, 2000; Lixa et al., 2010). As a conservation bio- a recent meta-analysis of small-scale fi eld studies reveal logical control measure, these species of weeds can be used that an increase in plant diversity, realized by a minimal to increase the abundance of coccinellids in or within the control of weeds, fosters the activity of generalist preda- borders of fi eld crops (Wäckers & van Rijn, 2012). In this tors in suppressing herbivorous pests (Dassou & Tixier, respect, it is of primary importance to investigate the prey 2016). Generalist predators can thus be a key component spectrum of coccinellids and their seasonal movement into of conservation biological control. Simple techniques for and from the rice fi eld. In particular, knowledge of coc- conservation of indigenous natural enemy diversity can cinellid trophic relationships would provide a better under- Final formatted article © Institute of Entomology, Biology Centre, Czech Academy of Sciences, České Budějovice. An Open Access article distributed under the Creative Commons (CC-BY) license (http://creativecommons.org/licenses/by/4.0/). 364 Shanker et al., Eur. J. Entomol. 115: 364–371, 2018 doi: 10.14411/eje.2018.036 standing of terrestrial food webs and the alternative food abundance was averaged for the fi ve locations in order to reveal items that enhance the survival of these predators during the overall seasonal trend. periods when their main prey is scarce. Electrophoretic assessment of the prey of the The natural food of coccinellids can be ascertained in coccinellids several ways (Harwood & Obrycki, 2005; Weber & Lund- A polyacrylamide gel electrophoresis (native PAGE) method, gren, 2009; Hodek & Evans, 2012). Most studies are based modifi ed from Murray & Solomon (1978) and Giller (1982, 1984 on the dissection of their gut contents. Other techniques and 1986) was used to characterize banding patterns for different such as radio-labelling of prey, microscopic examination species of prey and predator. Esterases were studied because they of faecal samples, electrophoresis, stable isotope analysis are ubiquitous enzymes in organisms and as they have species and ELISA using antibodies have been used in fi eld stud- specifi c patterns they can be used to discriminate between the dif- ferent species of prey (Murray & Solomon, 1978). ies with varying degrees of success (reviewed by Michaud Two coccinellid species, Harmonia octomaculata (Fabricius) & Harwood, 2012). Recent advances in molecular biology and Micraspis discolor (F.) and three hopper species, the green have resulted in the development of group-specifi c or spe- leaf hopper (GLH) Nephotettix virescens Distant, the brown cies-specifi c DNA primers, which can be used in standard plant hopper (BPH) Nilaparvata lugens Stal and the white backed or multiplex PCR to identify the prey in a predators’ gut planthopper (WBPH) Sogatella furcifera Hovarth, were used to (Michaud & Harwood, 2012). While this method is the confi rm the unique banding patterns for coccinellids and their most accurate for detecting a given type of prey it is expen- prey. Adults of each species were released individually into 100 × sive when screening a large number of predators for sev- 41 mm polystyrene Petri dishes with a 4-cm diameter ventilation eral types of prey. In addition, the development of an ap- hole in the lid covered with a 0.05 mm fabric mesh (SPL Life Sci- ences Inc., Korea). Five third-instar nymphs of each of the three propriate primer is rather time-consuming. In fact, primer species of planthopper from glasshouse cultures were placed in design based on sequenced individuals, evaluation of prey the Petri dishes. There were fi ve replicates of each combination specifi city using a set of non-target organisms, primer sen- of predator and prey, totalling 15 adults per taxa. Beetles were re- sitivity and laboratory feeding trials to estimate the DNA moved for analysis after they were observed to fed on one hopper. half-detectability time should be done before undertaking In order to assess the feeding behaviour of coccinellids collected a fi eld study (Harwood & Obrycki, 2005; Hodek & Evans, from fi eld, the insects were analyzed in the following categories: 2012). Considering the small size and cryptic nature of their Adult beetles of H. octomaculata, M. discolor, Propylea dis- prey, an analysis of the prey-specifi c enzymes in the gut of secta (Mulsant), Coccinella transversalis Fabricius, Cheilomenes generalist predators, such as coccinellids, could be used to sexmaculata (Fabricius), Scymnus nubilus Mulsant and Bru- moides suturalis (Fabricius) were collected in the fi eld between more rapidly identify their prey and defi ne their feeding 8:00 and 9:00, placed in a refrigerator below 4°C within 1 h of patterns. In this study, we used an electrophoretic approach collecting and then quickly analyzed in order to preserve their rather than PCR-based methods. Our approach proved to prey content. be useful in a fi rst assessment of the predators’ food. In par- All possible homopteran prey viz., Aphis gossypii Glover, ticular, when the prey and predator enzyme banding pat- Aphis craccivora (Koch), Schizaphis graminum (Rondani), Ci- terns are distinct, electrophoresis can be a cheap and quick cadulina bipunctata (Melichar), Thaia oryzivora Ghauri and Zy- tool for the detection of prey items in fi eld-caught preda- gina maculifrons (Matsumura) were collected from weeds and tors (Solomon et al., 1996). It has already been shown that preserved