Ecological control service of the predatory natural enemy and its maintaining mechanism in rotation-intercropping ecosystem via wheat-maize-cotton

Ecosystem can offer regulating services to change biodiversity patterns and ecological processes and then affect the prevalence of crop pests. Biological pest control could serve as an environmentally friendly ecological control service to suppress crop pests and decrease pesticide use by maintaining or increasing natural enemies. However, few study focus on the explicit process of natural enemies, pest dynamics, quantitative assessment and maintaining mechanism of ecological control service in multi-crop farmland landscape system for the whole crops growing cycle. Here, an experimental model of rotation-intercropping ecosystem via wheat-maize-cotton was planned for three consecutive years to response above questions. Our result found the rotation-intercropping ecosystem help to increase the abundances of the dominant natural enemy, Propylea japonica adults and then promoted aphid reduction in center cotton plots. In crops growing cycle, many predators maintained in wheat from Mid-April to late May, then the predator moved to inhabit in maize before wheat harvest during early June. During the intercropping period of maize and cotton, the predator would prefer to back and forth inhabit in maize and travel to cotton to actively prey on cotton pests. Quantitative evaluation of pest control based on a new built method of Ecological Control Service Index (ESI) found that crop diversity has highly efficient control function in rotation-intercropping ecosystem. The values of ESI at the peak of cotton aphids on center cotton plots were 0.80 in 2012, 0.31 in 2013 and 0.61 in 2014, respectively. The sustainably available prey resources in multi-crops ecosystem and maize as crop habitat with conditions of relative low temperature (28.5℃) and high humidity (68.3 %) are beneficial to maintain the predator natural enemy and ecological control service. Thus, our results suggest that giving full play to the ecological control service of crop diversity in rotation-intercropping ecosystem is beneficial to decrease crop pests and pesticide use, especially under the aggravating agricultural intensification. These findings support growing efforts from landowner, field manager and policy-makers to promote this ecosystem service via designing crops patterns and adjusting crops growing circle in regional agroecosystem.