Seasonal dynamics of spider diversity and rice planthopper abundance in organic farming paddy rice-duck field

To explore the approaches and methods of insect pest management in organic farming paddy fields,a two-year investigation was conducted on the quantitative dynamics of spiders and rice planthoppers in organic farming middle-late rice-duck field in East China across rice growth season,with the conventional paddy fields(Ⅰ and Ⅱ,according to the pesticide application rate) as the control.A total of 9-10 families of spiders were recorded for different farming systems.The spider's species diversity as measured by Shannon index was in the order of conventional paddy field Ⅱ conventional paddy field Ⅰ organic farming rice-duck field,while the dominance index was the highest in organic farming rice-duck field.The spider's abundance in early growth season was lower in organic farming rice-duck field than in conventional paddy fields Ⅰ and Ⅱ,while that in middle and late growth seasons was in reverse.Rice planthopper's abundance in organic farming rice-duck field had a greater seasonal fluctuation, compared with that in conventional paddy fields.The abundance of rice planthoppers was greater in organic farming rice-duck field than in conventional paddy fields,but the abundance of spiders had less difference,resulting in a lower spider/rice planthopper ratio in organic farming rice-duck field than in conventional paddy fields across rice growth season.The results suggest that the pest control in organic farming rice-duck field confronts serious challenge,and it is necessary to explore practical and feasible ecology-based management methods.