Flora surrounding rice fi elds as a source of alternative prey for coccinellids feeding on the pests of 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 surrounding 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 (Melichar), 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 corresponding 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 colonization of rice fi elds by coccinellids.