The spider diversity and plant hopper control potential in the long-term organic paddy fields in sub-tropical area, China

Previous studies showed that organic farming augmented natural enemies and enhanced pest control in the agroecosystem, but the effect may change over time, as long-term application of different cultivation methods would gradually affect the agricultural systems. In this paper, spider diversity and its plant hopper control potential were assessed in paddy fields cultivated organically for 5 (OR5), 10 (OR10) and 15 (OR15) years and in conventional paddy fields (CR). The results showed that the abundance, richness and Pilou evenness of spiders in organic paddy fields were significantly higher than those in conventional paddy fields were, but no significant difference found between OR5, OR10 and OR15. There was no significant difference between Shannon Wiener index (H') of spiders in organic and conventional paddy fields. There was no distinct difference in spider assemblage composition between conventional and organic paddy fields, and a considerable overlap between the organic paddy fields with different organic farming period. Plant hopper was less abundant in organic paddy fields than conventional ones in rice blooming stage, but there was no difference in other rice growth stages. A higher number of the spider species in organic paddy fields had large temporal overlap with plant hopper than that in conventional fields. Adopting organic practices in paddy fields can maintain a high diversity of spiders across rice paddy ecosystems, although there was not significant increase of spider diversity over time after five years since transition.