Effects of Winter Cover Crops on Rice Pests, Natural Enemies, and Grain Yield in a Rice Rotation System

Rotations that include winter cover crops are widely used in agricultural systems and can provide numerous agroecological and economic benefits. However, the effects of winter cover crops on arthropod diversity, specifically rice pests and related natural enemies in rice rotation systems, are still largely unknown. We compared the effects of three winter cover crops, rapeseed, Brassica napus L. (Brassicales: Brassicaceae), Chinese milkvetch, Astragalus sinicus L. (Fabales: Fabaceae), and garlic, Allium sativum L. (Asparagales: Amaryllidaceae), on arthropods species diversity and evenness, densities of populations of major rice pests and major natural enemies, and grain yield in an experimental double cropping rotational rice field in Jiangxi Province, China. We did not observe any effects of cover crops on arthropod species diversity and evenness. The presence of prior cover crops also had no effect on the number of plants infested by the two major rice pests, Chilo suppressalis Walker (Lepidoptera: Pyralidae) and Cnaphalocrocis medinalis (Guenee) (Lepidoptera: Pyralidae). Our study did not show any effects of rapeseed and Chinese milkvetch on grain yield. However, grain yield was increased in the garlic treatment. Our results suggest that although the winter cover crops we tested in our study do not affect the number of rice plants infected by major rice pests, they do not negatively affect the arthropod community and grain yields in rice rotation systems. Therefore, planting of winter cover crops may increase agricultural land utilization and have an overall economic benefit in rice rotational systems.