Abstract
Pesticides are commonly used in food crop production systems to control crop pests and diseases and ensure maximum yield with high market value. However, the accumulation of these chemical inputs in crop fields increases risks to biodiversity and human health. In addition, people are increasingly seeking foods in which pesticide residues are low or absent and that have been produced in a sustainable fashion. More than half of the world’s human population is dependent on rice as a staple food and chemical pesticides to control pests is the dominant paradigm in rice production. In contrast, the use of natural enemies to suppress crop pests has the potential to reduce chemical pesticide inputs in rice production systems. Currently, predators and parasitoids often do not persist in rice production landscapes due to the absence of shelter or nutritional sources. In this study, we modified the existing rice landscape through an eco-engineering technique that aims to increase natural biocontrol agents for crop protection. In this system, planting nectar-rich flowering plants on rice bunds provides food and shelter to enhance biocontrol agent activity and reduce pest numbers, while maintaining grain yield. The abundance of predators and parasitoids and parasitism rates increased significantly in the eco-engineering plots compared to the insecticide-treated and control plots. Moreover, a significantly lower number of principal insect pests and damage symptoms were found in treatments where flowering plants were grown on bunds than in plots where such plants were not grown. This study indicates that manipulating habitat for natural enemies in rice landscapes enhances pest suppression and maintains equal yields while reducing the need for insecticide use in crop fields.
Highlights
Rice (Oryza sativa) is the most important staple food for a large part of the world’s human population, especially in East and South Asia, the Middle East, Latin America, and the West Indies[1].Globally, rice provides more than one-fifth of the calories consumed by humans
The results show that the highest number of grasshoppers (GHs) and yellow stem borers (YSBs) were found in T3 during Boro 2015–16 (Fig. 2A)
We show that modification of existing rice landscapes via ecological engineering techniques in which nectar-rich flowering plants are grown on rice bunds surrounding rice fields promotes biocontrol agents, reduces pests and maintains crop yields
Summary
Rice (Oryza sativa) is the most important staple food for a large part of the world’s human population, especially in East and South Asia, the Middle East, Latin America, and the West Indies[1].Globally, rice provides more than one-fifth of the calories consumed by humans. Rice yield losses increased due to widespread outbreaks of the brown plant hopper (Nilaparvata lugens)[2,3], rice leaffolder (Cnaphalocrocis medinalis Güenée)[4], small brown planthopper (Laodelphax striatellus Fallen), rice hispa (Dicladispa armigera Oliver), yellow stem borer (Scirpophaga incertulas L.) and white-backed planthopper (Sogatella furcifera Horvath) These pests cause hundreds of millions of dollars of losses every year and threaten food security in regions where rice is the staple food[5]. Under eco-agricultural management, bunds are enriched with nectar producing plants and non-rice habitats used to grow perennial plants to provide additional food and shelter for natural enemies[43,44] These improved habitat-characteristics can greatly influence natural enemy longevity, fecundity and behavior and lead to reduced pest abundance[42,45,46,47,48]. We contrasted three treatments; growing nectar-rich plants (marigold, cosmos, sunflower and sesame) on bunds (Fig. 1) coupled with no insecticides on rice (hereafter T1), compared to fallow bunds with (T2), and without prophylactic insecticide use on rice (T3)
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