Integrated Pest Management (IPM) is an effective, environmentally sound approach to pest management (Kabir and Rainis, 2015). It provides for the protection of beneficial insects, as well as prevention of secondary pest outbreaks, pest resurgence, and the spread of disease. IPM strategies aim to protect air, water, and soil resources while meeting specific production objectives (Mangan and Mangan, 1998; National Pesticides Information Center in USA, 2015¹). IPM combines the use of a variety of pest-control methods in a way that facilitates biological control of pest insects in crops in order to improve economic, public-health, and environmental outcomes. Key components of effective IPM strategies are monitoring of pest populations, recognizing pest-resistant plant varieties, and modifying cultural, mechanical, chemical, and biological controls as needed to achieve production goals (Adams, 1996). Including farmers' traditional agricultural knowledge of insect behavior and life cycles is essential for developing a successful IPM plan (Petit et al., 2003; Roitberg, 2007; Vinatier et al., 2012), as is taking into account their current agricultural practices and experience in a given agro-ecosystem (Rahman, 2012; Craig, 2015).

The focus of IPM is to protect and encourage natural predators of pest insects (Naranjo et al., 2015). Understanding the life cycles and the interactions of pest insects and predators provides the basis for successful design and implementation of an IPM strategy. In addition to taking advantage of predator-prey interactions, IPM often includes the judicious use of pesticides. Organic food systems employ similar methods but limit the use of pesticides produced from “non-natural” or synthetic sources (U.S. Environmental Protection Agency [US-EPA], 2014²). Worldwide, chemical pesticides have played a vital role in providing an abundant and inexpensive food source (US-EPA, 2015³). Despite an increase in food production, however, the persistent overuse of chemicals has resulted in a number of adverse environmental impacts such as, outbreak of secondary pests, decreasing of beneficial insects and the accumulation of toxins in the food webs (Arora et al., 2014). Continued research and development of sustainable and effective agricultural-pest-management techniques is essential if farmers are going to successfully adopt environmentally friendly pest-management strategies (Pretty and Bharucha, 2015).

As a result of the world's unprecedented population growth, food-production systems are being pushed to maximum efficiency (International Institute for Environment and Development [IIED], 2015⁴). Among the widely cultivated food crops, cereals are recognized as an important component of food security. The Food and Agriculture Organization (FAO)⁵ estimates that demand for food will more than double by the year 2050 (2009). To meet this demand, cereal-crop production in developing countries must increase by 40% (Eze and Echezona, 2012). Rice, one of those cereal crops, is a staple food source for more than fifty percent of the world's population (International Rice Research Institute [IRRI], 2006⁶). Rice crops either directly or indirectly sustain 3 billion people (Food and Agriculture Organization Stat. [FAOSTAT], 2012⁷). In 2010, 154 million hectares of rice was cultivated worldwide FAOSTAT, 2012. Asia comprised 137 million hectares, with 48 million hectares harvested in Southeast Asia (FAOSTAT, 2012). In Bangladesh 80 percent of agricultural land is dedicated to rice cultivation (Department of Agriculture Extension in Bangladesh [DAE], 2010⁸).

Two-hundred and sixty-six insect species have been identified in rice ecosystems (DAE, 2011⁹). Of these, 42 species are considered to be pests (Srivastava et al., 2004). Pest insects can be categorized as either minor or major pests. Different pest insects cause severe damage to rice crops at different growth stages. The degree of damage depends on the growing season and environmental conditions (Khaliq et al., 2014). One pest species, Yellow Stem Borer (YSB-Scirpophaga incertulas; Lepidoptera Crambidae), is considered to be a major rice pest (Chatterjee and Mondal, 2014). Rice plants damaged by this insect develop unhealthy tillers and hills, Dead Heart (central leaf drying), and White Head (grain-less panicles), all of which affect the overall yield (Satpathi et al., 2012). According to DAE (2011) YSB populations can be reduced through several IPM methods, including: light trapping (placing a light source inside a funnel-shaped trap), hand picking eggs from rice leaves (Leaves with egg masses are removed from plants by hand during tillering and booting stages), sweeping (using a funnel shaped net to capture insects), perching (installing a branch or pole which serves as a resting place for predatory birds), cultivation of insect resistant rice varieties, using bio-agents [releasing predator insects such as Long horned grasshopper Conocephalus longipennis (Haan)], applying Economic Threshold Level (ETL) based insecticides (The ETL is the point at which the value of the crop destroyed exceeds the cost of controlling the pest). Most rice farmers currently rely on heavy insecticide applications rather than IPM strategies for pest insect control (Mohiuddin et al., 2009).

We believe the wide-scale adoption of IPM in rice agro-ecosystems could provide a net benefit to farmers. The IPM program used in this study is from the “Farmer Field School” (FFS) model. Continuing farmer education and training play a vital role in advancing IPM practices, and this innovative IPM-education program provides training for the identification of beneficial and pest insect species, as well as the recognition of associated impacts on crop yields (Craig, 2015).

For this study our IPM strategy consisted of egg-mass collection, perching, sweeping, and ETL-based insecticide application. Non-IPM treatments consisted of egg-mass collection, perching and sweeping without insecticide application, prophylactic insecticide application only, and current pest-management practices. We studied the effects of IPM and non-IPM strategies on rice-yield components. Our working hypothesis was that fields in which we used IPM strategies would have less crop damage and higher rice yields compared with fields treated with non-IPM strategies.

Rice has been cultivated by humans for 5000 years. Through those millennia farmers developed increasingly efficient systems of coping with environmental factors, including pest insects that threatened yields. When modern pesticides became available, they were marketed to farmers as a panacea for eradicating pests, saving labor, and increasing yields. Pesticides, however, came with a cost: environmental degradation and decreased crop resilience. To mitigate some of these negative impacts, IPM was developed as a pest-management strategy designed to blend traditional, knowledge-based pest-control methods and judicious use of pesticides. The goal is to improve yields, increase crop resilience, and end damage to environmental systems associated with overuse of pesticides.

When properly implemented, a pest-management strategy enriches ecosystem services and provides a sustainable food source for a range of beneficial insects (Hillocks and Cooper, 2012). Healthy rice agro-ecosystems support a diverse insect community by maintaining a complex food web (Redfern et al., 2015). The insects participating in this food web can help maintain ecosystem function as long as predator species (insects and others) continue to flourish (Allara et al., 2012). Two hundred and sixty-six insect species have been documented in rice agro-ecosystems (DAE, 2011). Predator insect species account for 64.74% of all insects, with the remainder classified as pest species (Lou et al., 2013). Since pesticides have become available, the number of predator species and populations within surviving predator species have declined. Current non-IPM pest-management strategies often involve over application of pesticides (Table 1), which has, in turn, resulted in decreased populations of beneficial insects and increased pest damage to a number of critical crop-yield components (Abrol, 2013). In this study, rice yield was typically higher in the IPM-treated plots as compared with plots treated with pesticides only (Tables 3, 6).

Rice tillers, hills, leaves, panicles, and grains are the most important yield components of rice crops. Reduction in the number of tillers, drying of central leaves (Dead Heart), and damage to the panicles (White Head) are indications of stem-borer infestation often visible in rice fields (Paul, 2007). When stem-borer damage becomes apparent, farmers often apply inappropriately large quantities of pesticides (Table 1). IPM and pesticide-only control methods both have a significant effect on rice-yield indicators. We found the incidence of Dead Heart and White Head were lower than 5% in the IPM treated plots (Tables 2, 6), which, in fact, is lower than established critical limits (5%). Egg masses were 2/m² or 1 moth/ m² from mid-tillering to booting stage.

As part of the IPM treatment, we applied ETL-based insecticides strategically, which minimized the pest population in IPM-treated plots. As a result rice yield was 7.5 ton/ha in the IPM-treated plots. These yields were significantly higher than the other treatments (Table 3). Singh et al. (2014) conducted similar research on the effectiveness of IPM for YSB in rice- and wheat-cropping systems. They found similar incidence of Dead Heart and White Head (<5%) in their IPM treatments. Other studies have shown that a well-designed IPM program can control pest insects in an ecological manner (Bux et al., 2013; Ehi-Eromosele et al., 2013). By reducing the incidence of Dead Heart and White Head in YSB-infested rice fields, IPM improves rice yields (Bux et al., 2013). It has also been demonstrated by DAE (2011) that IPM approaches minimize pest damage while maximizing yields and improving overall environmental quality (U.S-EPA, 2015).

According to Abrol (2013), IPM strategies that use appropriate ETL-based insecticide applications can be an effective method for managing pest insects. Rodrigo et al. (2013) demonstrated that appropriate pesticides used at application rates compatible with IPM strategies are beneficial for the control of rice pests during germination, vegetative stage, and flowering stage. In our study insecticides were applied at the tillering and booting stages in the IPM-treated plots (T₂) across all locations (Table 1). We found that higher than recommended rates of Cartap (0.15 g/m², recommended 0.14 g/m²) were frequently applied in farmers' fields (Table 1). To mirror conventional practices, our study included treatments with three and four insecticide applications (T₃ and T₄, Table 1). We determined that IPM-treated plots (T₂) provided significantly higher yields and that conventional practices might have a negative impact on rice production. This result agrees with earlier studies, which found that pest-management systems that fail to use IPM strategies have lower average rice yields (Sattar et al., 2004; Alam, 2013).

Pest-control strategies that include appropriate pesticide use have consistently been shown to increase rice production (Arora et al., 2014; Muck, 2015). Jacobsen and Hjelmso (2014) report that heavy pesticide use often has a higher cost-to-yield ratio than IPM methods. Our IPM-treated plots had lower pesticide costs than non-IPM treatments. Net economic losses for non-IPM techniques have been documented in an annual revenue report (Consultative Group for International Agricultural Research¹¹ [CGIAR]), 2010; Farrar et al., 2015). Measures of productivity and sustainability are frequently higher in IPM-managed farms than non-IPM farms (Côte et al., 2009; Ortiz et al., 2009; Sharma et al., 2015). These studies conclude that IPM techniques are yield efficient, environmentally friendly, and can be the foundation of sustainable cropping systems (Hall et al., 2013). An over-reliance on pesticides has proven to be unsustainable, less cost effective, and less efficient for pest control (Berg and Tam, 2012; Rasmussen et al., 2012; Alam, 2013; Rodrigo et al., 2013).

Farmers often over-apply pesticides or spray at inappropriate times because they lack knowledge of the negative impacts associated with these practices (Jepson et al., 2014). Contributing to this is a lack of understanding about how insect life cycles correspond to the life stages of rice plants and at what stages pesticides are most effective. Additional education and training is needed to better inform farmers of responsible pest-management techniques and appropriate pesticide-application techniques (Parveen, 2010). Increasing the number of IPM-trained farmers will result in smaller quantities of pesticides being released into rice agro-ecosystems, increased rice yield, and improved human health and environmental quality (WHO, 2010¹²; Berg and Tam, 2012; Andersson et al., 2014; Nerilo et al., 2014; Sharma et al., 2015).

In the search for higher yields, the excessive use of pesticides might be the catalyst for current and future ecological crises. Potential problems include pesticide resistance, resurgence of insect pests, pesticide poisoning, environmental toxicity, elimination of predator species, negative outcomes for other non-target organisms, disruption in the food web, increased prevalence of pesticide residues in food, and reduced rice yields (Aktar et al., 2009; Sharma et al., 2015). These problems could be avoided by implementation of well-designed IPM strategies (Mohd Fuad et al., 2012; Srinivasan, 2012; Sharma et al., 2015). Despite several IPM techniques specifically designed for rice production, however, adoption remains low because of the perception that “chemical-free” strategies are less effective than heavy insecticide application.

IPM practices can be used for effective pest control in rice agro-ecosystems. The principle advantage of this technique is that rice yields increase as the resilience of the cropping system increases. Our study demonstrates that a well-designed IPM strategy can have a positive effect on yield components. In our study, rice variety BRRI Dhan 29 yielded 7.3–7.5 ton/ha in the IPM-treated plots. According to BRRI¹³ (2015), the cultivar BRRI Dhan 29 is capable of yields from 6 to 8 ton/ha in Bangladesh agro-climatic zones. Despite the demonstrated advantages, adoption of IPM strategies might not happen quickly. It will be necessary to educate farmers about the environmental impacts associated with improper pesticide use and the consequences of those impacts on human communities and future food production. Further, in developing appropriate IPM strategies, it will be necessary to examine current pest-management practices and build on farmers' current and traditional knowledge. Additional research is needed to develop an understanding of farmers' traditional pest-management knowledge base, identify insect-resistant rice varieties, analyze the patterns of pesticide use, investigate constraints to controlling rice pests, examine farmers' awareness of environmental pollution caused by pesticide applications, and explore additional alternatives to pesticide use.

MA served as research team leader and was responsible for the study design, data collection, analysis and interpretation, and manuscript preparation. AC helped with manuscript preparation, edited the manuscript, and provided feedback on study design and data analysis. MH contributed to data analysis and interpretation. MI optimized the BRRI recommended agronomic practices utilized in this study. EH provided labor, hospitality, and administrative support. SaBH was responsible for data collection, tabulation, and provided an economic analysis of the yield data. ShBH helped with data collection. MH provided administrative assistance, aided in data collection, and provided information on relevant public health issues.