Arthropod Diversity in Rice nurseries in North-Eastern Zone of Tamil Nadu

Abstract

Agricultural systems are often considered by ecologists as disturbed, depauperate, and evolutionarily recent. But tropical rice agro-ecosystem is one exception due to its ecological complexity resulted by the long ecological complexity resulted by the long ecological history and wide geographical distribution. Rice nursery is very similar to natural grassland and offers a wide scope for studying the biodiversity due to the presence of arthropod fauna.

A survey was conducted in five rice nursery fields in the same period in three villages of two districts of the north eastern zone of Tamil Nadu: Budur, Kavarapettai and Narasingapuram of Tiruvallur district, and Kavur and Malaiyambakkam of Kancheepuram district during Sornavari season,2003(April to August). The rice cultivar was uniformly ADT 43, a short duration variety. No chemical pesticide was applied in the nursery fields and the seedlings were of uniform age. Fifty double sweep net samples were taken to study arthropod diversity. The specimens sorted out were grouped into three guilds, viz., pests, entomophages and neutrals, and their relative abundance was worked out. .

The overall observations revealed that a wide range of arthropod fauna were present in the rice nursery fields. The neutrals were the most dominant guilds in four out of five locations. The relative abundance range from 30.22 to 67.13% .This guild was followed by the pests, which ranged from 17.5 to 48.58%. The abundance of entomophages ranged from 13.32 to 24.36%. Among the locations, the maximum relative abundance of pest and entomophage guilds was observed in Narasingapuram. The maximum relative abundance of neutrals was observed in Budur. The green leaf hopper, white flies, white-bat plant hopper, grass hoppers and trips were the major pests. The pre dominant entomophages were the spiders, parasitic hymenoptera and ground beetles. Dipteran flies and hydrophilids were the pre dominant neutrals observed. It may be concluded that rice nursery field supports a wide range of arthropods. The neutrals help in the buildup of carnivorous (entomophages), which ultimately check the pest population.