Effect of diversified cropping on insect pests and natural enemies in agroecosystems

The history of diversified cropping can be dated back to the era of man’s evolution that followed hunting and gathering, and this form of cropping has stood the test of times to be still as an important farming practice in modern agriculture. In recent years, to control insect pests using diversified cropping has been the focus of agricultural research. Diversified cropping has direct effect on the occurrences, damages and behaviors of insect pests. Many researches have indicated that diversified cropping reduces, to a large extent, the occurrences and damages of insect pests. It has been noted in some cases, however, that diversified cropping systems fail to reduce or even increase insect pest damages to crops. Diversified cropping affects not only natural enemy populations, but also parasitic and predation rates of the populations. Diversified cropping also influences natural enemies by disturbing the orientation, foraging and dispersal behaviors of the enemies. This study summarized the effects of diversified cropping on insect pests and natural enemies in agroecosystems. From a review of domestic and international research reports, the study also highlighted current problems and future researches on diversified cropping systems. Seven hypotheses (physical obstruction, visual camouflage, host plant odor masking, using repellent chemicals, altering host plant odor profiles, enemy hypothesis and resource concentration hypothesis) and one theory (appropriate/inappropriate landing) were introduced regarding the relationship between diversified cropping and insect pests. The hypothesis and theory largely explained the relationship, but none of them was fully elucidated the mechanisms of the effects of diversified cropping on insect pests and natural enemies in agroecosystems.