Arthropod Diversity In Non-Crop Habitats At Margins Of Paddy Fields Of Different Types

To explore ecological management approaches to rice pest control, a survey of arthropods was made across the rice-growing season from weeds, soybean and sesame at field margins of paddy fields under the four management regimes including organic duck-rearing, low-pesticide with duck-rearing, low-pesticide without duck-rearing, and conventional in east China paddy fields. The study was designed to evaluate biodiversity in non-crop habitats in paddy fields under variable pest-management regimes, which would be useful in the assessemnt of potential of biodiversity in pest control practices. The main results are as followed below.1. Arthropod diversity on weeds at paddy field margins of different types in 2009The survey uncovered 192 species in 69 families,11 orders from 2 classes.They included insects of 152 species in 59 families of 10 orders, and arachnids of 40 species in 10 families.The functional groups were consisted of 8 predatory insect species,79 parasitoids,62 phytophagous insects and 3 neutral insect species. The arthropods uncovered from the survey included 147 species (123 insectsand 24 spiders) at organic duck-rearing paddy field margings,140 species (107 insects and 33 spiders) at low-pesticide-duck paddy field margins,114 species (83 insects and 31 spiders) at low-pesticide non-duck paddy field margins, and 83 species (54 insects and 29 spiders) at conventional paddy field margins. Abundances of spider natural enemies obviously increased at rice-duck fieldmargins by 2.12-3.59 times as many as those at no-duck field margins. Species richness and abundance of insects, including phytophagous, parasitoid, and predatory insects, were highest at organic duck-rearing paddy field margins, followed by those at low-pesticide-duck paddy field margins, but spiders and neutral insects was highest in diversity and evenness and lowest in dominance rank at low-pesticide-duck paddy field margins. Species richness of natural enemies at organic duck-rearing paddy field margins was higher than that at conventional paddy field margins.The survey suggested that arthropod biodiversity was better conserved at the margins of paddy fields with organic and low-pesticide application than the conventional paddy fields.2. Arthropod diversity on weeds at paddy field margins of different types in 2010The survey uncovered 167 species from 67 families,11 orders from 2 classes. It included insects of 136 species in 58 families of 10 orders, and arachnids of 31 species in 9 families; the functional groups were consisted of 6 predatory insect species,76 parasitoid insect species,51 phytophagous insect species,3 neutral insect species. The arthropods uncovered from the survey included 126 species (102 insect species,24 spider species) at organic duck-rearing paddy field margings,109 species (81 insect species,28 spider species) at low-pesticide-duck paddy field margins,84 species (65 insect species,19 spider species) at low-pesticide non-duck paddy field margins and 102 species (78 insect species,24 spider species) at conventional paddy field margins. In terms of species richness and abundances of arthropods the organic duck-rearing paddy field margins was followed by low-pesticide-duck paddy field margins, which was followed by low-pesticide non-duck paddy field margins. Organic duck-rearing paddy field margins and low-pesticide-duck paddy field margins were similar in parasitoid wasp abundances, by 1.73 times more than low-pesticide non-duck paddy field margins and by 1.49 times more than conventional paddy field margins. An obvious link in abundances between spiders and planthoppers on organic duck-rearing field margins weeds and low-pesticide-duck paddy field margins, but no such a link was exhibited in the low-pesticide non-duck paddy field margins and conventional field field margins. The survey suggested that the organic field margins in natural enemies species richness obvious greater than the conventional, the affectness of ecology manage pests was apparent. The diversity index and eveness index of insect community on low-pesticide-duck paddy field margins at best most, organic duck-rearing field marginss taken the second place, low-pesticide non-duck paddy field margins was adverse. The results suggested that in terms of insect community stability the low-pesticide-duck paddy field margins was greater than the organic duck-rearing field margins, which was greater than the low-pesticide non-duck paddy field margins.3. Arthropod diversity on sesame and soybean at paddy field margins of different types.The survey uncovered 172 species in 76 families,12 orders from 2 classes. They included 103 natural enemies (33 spider species,6 predatory insect species,64 parasitoid insect species),64 phytophagous insect species. The organic duck-rearing field margins had more spiders and insect natural enemies than the conventional, with spiders by>4.5 times and insect natural enemies by>1.5 times in species richness and abundance on organic duck-rearing field margins greater than on the conventional. As for plants in field margins, soybean in the conventional field margins was greater in insect species richness and abundances than soybean in the organic duck-rearing and sesame in the conventional field margins, while it was similar in diversity indices between soybean and sesame in the organic duck-rearing field margins and between weeds in the organic duck-rearing and conventional field margins. The survey suggested that natural enemies were better conserved in organic duck-rearing field than in conventional field, and growing soybean and sesame in field margins with conventional farming would promote conservation of arthropod community.