Flora surrounding rice fields as a source of alternative prey for coccinellids feeding on the pests of rice

Chitra Shanker,Sampathkumar Muthusamy,Gururaj Katti,Lydia Chintagunta,Amudhan Srinivasan,Sunil Vailla

doi:10.14411/eje.2018.036

Chitra Shanker, Sampathkumar Muthusamy + Show 4 more

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https://doi.org/10.14411/eje.2018.036

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Abstract

Coccinellids are effective predators and a key component of the predator guild in rice ecosystems. In order to enhance their efficacy, a study was undertaken to assess the seasonal movement of coccinellids into rice fields and the role of the surrounding flora on their colonization. The seasonal abundance of coccinellids and their prey was recorded on the rice crop and the surrounding flora 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 (Melichar), Schizaphis graminum (Rondani), Sitobion sp., Thaia oryzivora Ghauri and Zygina maculifrons Matsumura. Of the species of coccinellids recorded in rice fields, 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 profiles indicated that the leafhoppers and aphids on the weeds were the prey of the coccinellids before they colonized the rice fields. The coccinellids recorded on the weeds showed bands corresponding to the insects present on the weeds. Beetles collected from rice fields 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 flora. The results indicate the importance of surrounding flora in the conservation and colonization of rice fields by coccinellids.

Highlights

Generalist predators play an important role in regulating insect pests in agricultural ecosystems (Joon & Seung, 2001)
The phytophagous insects associated with weeds included A. gossypii, A. craccivora, Schizaphis graminum and Sitobion sp.; C. bipunctata, T. oryzivora, Z. maculifrons (Hemiptera: Cicadellidae) and all stages of Altica cyanea (Weber) (Coleoptera: Chrysomelidae)
Many adults of M. discolor and H. octomaculata were recorded on Acmella uliginosa (Sw.) Cass., Ageratum conyzoides, Caesularia axillaris Roxb., L. and Eclipta alba (L.) Hassk. (Family: Asteraceae) and Echinocloa colona (L.), (Family: Poaceae), when the rice crop was near the harvesting stage and the hopper population had started diminishing in the field

Summary

Introduction

Generalist predators play an important role in regulating insect pests in agricultural ecosystems (Joon & Seung, 2001). Their ecological role in pest management was underestimated in the past, recently, the importance of generalist predators has been reconsidered (Symondson et al, 2002). A recent meta-analysis of small-scale field studies reveal that an increase in plant diversity, realized by a minimal control of weeds, fosters the activity of generalist predators in suppressing herbivorous pests (Dassou & Tixier, 2016). Generalist predators can be a key component of conservation biological control. Simple techniques for conservation of indigenous natural enemy diversity can enhance natural control and prevent pest outbreaks. Some species of coccinellids are widely reported occurring in rice fields, where they mostly feed on aphids (Rekha et al, 2009; Shanker et al, 2013a)

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