Arthropod Biodiversity In Paddy Fields Under Different Management Regimes

Duck-rearing in paddy fields is one of farming systems in organic rice production. Rice-duck integrated farming, an ecology-based agricultural practice, has been carried out in numerous areas in rice-growing zones. To assess the potential for pest control by enhancing biodiversity in paddy fields, a two-year survey of arthropods was made across growing seasons in different types of paddy fields. The main results were as follows:1. The survey uncovered 167 insect species in 62 families,10 orders in 2009, including insect natural enemy of 96 species,23 families,6 orders, and insect pests of 65 species, 35 families,6 orders. In the organic paddy field insect natural enemies were composed of 68 species,20 families,4 orders, and insect pests of 41 species,26 families,6 orders. In the green paddy-field with duck insect natural enemies consisted of 68 species,19 families,4 orders, and insect pests of 44 species,30 families,6 orders. In the green paddy field without duck insect natural enemies included50 species,22 families,5 orders, and pests of 38 species,23 families,6 orders. In the conventional paddy field, insect natural enemies included 68 species,21 families,5 orders, and pests of 42 species, 26 families,6 orders, similar results were obtained in 2010.2. The main groups of pests collected in the two years were:â…°) Delphacidae, including Sogatella furcifera (Horvah), Laodelphgax striatellus, and Nilaparvata lugens (Stal);â…±) Cicadellidae, including Cicadella viridis, Nephotettix bipunctatus (Fabricius), and Inazuma dorsalis (Motschulsky);â…²) Thripinae, including Chloethrips oryzae(Wil.);â…³) Pyralidae, including Cnaphalocrocis medinalis Guenee) etc. The main insect natural enemies were:i) Coccinellidae, includingStethorus punctillum Weise, P ropy lea japonica Thunberg, and Harmonia axyridis(Pallas);â…±)Chrysopidae, including Chrysopa sinica Tjeder, and Ch. septempunctata Wesmeal),â…²)Braconidae, including Apanteles kariyai Watanabe, and A. cypris Nixon; iv) Ichneumonidae and Dryinidae, including Haplogonatopus japonicus E.et H, and H. atratus E.et H.; andâ…´) Chalcidoidea, including numerous unidentified species.3. The community structure was the most stable (narrow seasonal fluctuation in abundances) in the green rice paddy with duck, followed by the rice-duck field, and then by the green paddy field without duck, and by the conventional paddy field. There were differences in insect community between different types of paddy fields, but the similarity was lower the rice-duck farming and conventional rice paddy fields. The peaks of species richness and abundances were different among different types of paddy fields.4. The survey uncovered the kind of spider 36 species in 10 families, the dominant families were Tetragnathidae, Theridiidae, Linyphiidae, Lycosidae, Salticidae et al., and dominant species were Tetragnatha squamata, Erigonidium graminicolum Sundevall, Tetragnatha nitens, Tetragnatha Praedonia, Tetragnatha shkokiana, Tylorida striata, Theridonn octomacutatum, Erigone prominens, Pardosa astrigena, Pardosa nebulosa, Bianor aenescens, Evarcha albaria, and Marpissa magister etc. There was no difference in seasonal dynamics of spiders in different type of paddy fields, where spider abundances were greater during early, but smaller during the middle and later season, in the organic paddy field than in the conventional paddy field. Planthopper abundances fluctuated widely in the organic paddy field and the green rice paddy with duck, compared to the green rice paddy without duck and conventional fields. The overall abundance of planthoppers was greater in the organic paddy field than in the conventional fields. The two-year survey showed that there was a significant relationship in abundances between spiders and planthoppers in organic paddy field and green rice paddy with duck, but not in green rice paddy without duck and conventional paddy fields. The ratio of spider to planthopper abundances in the organic paddy field and green rice paddy with duck was lower than in the green rice paddy without duck and conventional paddy field.5. The ducks were active all day long and extensive in the paddy field, the foraging time accounted for 33%-46% in the daytime, and 54%-63% in the night, but there was no statistical differences(P>0.05) between foraging and resting time in terms of frequency. The daily rhythm was performed as three actively foraging time 8:00-9:00 and 10:30-11:30 am, and 14:30-16:30 pm during the day, and 2:30-6:00 during the night. The dissection of duck crops showed foliages and insects.