[EBOOK] Effect of crop-crop diversity on insert pests-A Meta analysis, M Srinivasa Rao et al., Central Research Institute for Dryland Agriculture (Saidabad P.O., Santoshnagar, Hyderabad - 500 059)

Considering the potential role of crop-crop diversity in managing the insect pest populations, several studies looked into the relationship between crop diversity and incidence of insect pests. In order to consolidate the understanding, several qualitative literature reviews were attempted to draw some generalizations, often based on the vote counting method. The generalizations drawn from such qualitative literature reviews suffer from lack of any statistical validity. This bulletin is an attempt to synthesize the studies on the relationship between the crop-crop diversity and incidence of insect pests through metaanalysis or a quantitative analysis of the results published. The data were taken from thirty-one studies which were related to agro-eco systems and conducted under field conditions and reported results as number of Insects in treatment and control. Taking these data effect size was computed and its statistical significance estimated. It was found that the effect size varied from -29.16 to 14.75 with a mean effect size of -1.5 indicating that the average density of Insect pests on an average was 1.5 standard deviations less in the crop-diverse situation as compared to the monoculture. In a majority of studies the effect size was observed to be negative indicating the reduction in insect pests in the presence of crop-crop diversity. The studies included in the analysis were found to be heterogeneous in terms of crops studied, insect pests and the experimental design. A separate analysis was conducted for lepidopteran and non-lepidopteran insect pests, which showed that the effect size was more in case of lepidopteran insects than in case of non-lepidopteran insect pests. The effect size in case of the natural enemies in crop diverse situations was found to be positive indicating an increase in their number. This finding corroborates the 'natural enemy hypothesis' as one of the pest reducing factors. Finally, attention Is drawn to the limitation of meta analysis as it is, like any other statistical tool, prone to be misued.

[EBOOK] Effect of crop-crop diversity on insert pests-A Meta analysis, M Srinivasa Rao et al., Central Research Institute for Dryland Agriculture (Saidabad P.O., Santoshnagar, Hyderabad - 500 059)

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