Abstract
The study on terrestrial arthropod communities in rice agro-ecosystems was conducted in Bathalagoda, Sri Lanka. A total of 342 arthropod species was documented comprising 282 species of insects in 90 families and 17 orders and 60 species of arachnids in 14 families. Eight taxa new to Sri Lanka are reported. Majority of the insects documented were hymenopterans, dominated by bees and ants. Based on feeding habits, majority of the arthropods recorded were predators (149 species), dominated by spiders. However, in the rice field proper, abundance of phytophagous rice pests was higher than that of predators. Density fluctuations of predators and parasitoids were positively correlated. Species richness and diversity of terrestrial arthropods increased gradually with crop age, but declined following application of pesticides. Species diversity (H') of terrestrial arthropods during vegetative, reproductive and grain ripening stages and the fallow period were significantly different. Diversity of terrestrial arthropods in the field proper positively correlated with crop age and height of the rice plant, and in field bunds with the weed cover. Findings indicate that a stable relationship could be maintained between rice insect pests and their arthropod natural enemies through minimal biocide applications and manipulation of weed cover in the rice agroecosystem. Key Words: Rice fields, arthropods, diversity, species richness, pests, natural enemies doi: 10.4038/cjsbs.v37i1.494 Cey. J. Sci. (Bio. Sci.) 37 (1): 23-48, 2008
Highlights
Origin and history of rice agro-ecosystems Rice cultivation is thought to be the oldest form of intensive agriculture by man (Fernando, 1977)
282 species of insects in 90 families and 17 Orders; 60 species of arachnids in 14 families constituting a total of 342 arthropod species were recorded from the rice field during the study
This study highlights the richness of the terrestrial arthropod fauna associated with an irrigated rice field ecosystem in Sri Lanka
Summary
Origin and history of rice agro-ecosystems Rice cultivation is thought to be the oldest form of intensive agriculture by man (Fernando, 1977). Cultivation of the crop probably dates back to the earliest age of man and, long before the era for which there is historical evidence, rice was a staple food and the first cultivated crop in Asia (Grist, 1965). Rice has been grown in Sri Lanka from time immemorial. It is generally believed that rice cultivation in Sri Lanka was started by IndoAryan immigrants before about 540 B.C where it was probably grown as a dryland crop (Grist, 1965; Perera, 1980). Based on the water regime, rice fields in Sri Lanka fall into three major categories; those under major irrigation schemes (41%), minor irrigation schemes (25%) and rainfed ricelands (34%)
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