One of the most significant crops in the world, rice (Oryza sativa L.), is a staple food for nearly half of the world's population (FAO, 2004) and for 2.7 billion people in developing Asian nations. With a yield of 483 million tons, rice is grown on around 148 million hectares of land worldwide, with Asia accounting for nearly 90% of the total area. Approximately one-fifth of the world's cropland used for cereal production is dedicated to rice cultivation.
Rice is highly susceptible to a variety of abiotic and biotic stresses which significantly affect its yield and quality. Abiotic stresses such as drought, salinity, heat, and flooding adversely impact rice growth, development, and grain productivity. Drought stress reduces photosynthesis and disrupts metabolic functions, while salinity leads to ion toxicity and osmotic imbalance, causing reduced seed germination and stunted growth (Munns and Tester, 2008). High temperatures during the reproductive stage lead to pollen sterility, poor grain filling, and yield loss (Jadadish et al., 2010), while submergence stress affects root respiration and nutrient uptake. Biotic stresses, on the other hand, include attacks by insect pests and diseases caused by fungi, bacteria, and viruses (Horgan et al., 2021). More than 300 insect pests are known to devastate rice fields in the tropics. Still, the majority of them do not cause sufficient economic harm to necessitate management measures, as the rice plants' robust compensatory mechanisms enable them to recover from such damage while in the vegetative stage. Nonetheless, particular insect pest species can destroy crops, and they often impact output and jeopardize food security when they are present in significant quantities.
One of the most significant pests that can cause significant damage in Puducherry in general and in the state's endemic areas in particular is the gall midge (Orseolia oryzae Wood-Mason) and it was noted as a regular pest in the Cauvery Delta region where rice is grown as the main crop during the kharif and rabi seasons each year. The rice gall midge maggots are producing galls in the rice's central leaf sheath, which leads to the development of silver shoots that are subsequently unable to produce panicles. In favourable agroclimatic conditions, the pest may reduce yield in the state of Puducherry by 10–25%. The rice case worm (Parapoynx stagnalis Zeller) utilizes its gills to breathe and is in its complete aquatic larval stage. It uses oxygen that has been dissolved in a drop of water that it carries in the rice-leaf casing to breathe. Rice in the seedling stage is susceptible to pest attacks, and this susceptability is more prevalent in fields with standing water (Nilamudeen et al., 2024). It creates cases and cuts rice leaves at a sharp right angle, which leads to a reduction in photosynthetic area, and accordingly, a reduction in yield. The primary sucking pests that cause significant financial losses in rice are hoppers, including the brown planthopper, Nilaparvata lugens (Stal.), and the green leafhopper, Nephotettix virescens (Distant). This insect's nymphs and adults both drain the plant's sap, which causes the rice plant to become chlorotic, wilt, and dry out. This feeding damage is often known as ‘hopper burn’, and up to 60% yield loss is common in sensitive rice cultivars attacked by the brown plant hopper. N. lugens also transmits the grassy stunt disease (Prasannakumar et al., 2015).
Chemical pest control, primarily through the use of synthetic insecticides, is a common practice in rice cultivation to mitigate pest infestations and ensure higher yields. Insecticides such as organophosphates (e.g., chlorpyrifos), carbamates, and pyrethroids are widely applied to control key pests, including rice stem borers, brown planthoppers, and leaf folders. Although these chemicals provide immediate pest suppression, their indiscriminate and prolonged use often leads to pesticide resistance, resurgence of secondary pests and environmental pollution. Moreover, residues of these chemicals accumulate in soil and water, posing severe health hazards to humans and non-target organisms. Chronic exposure to pesticide residues in rice has been linked to adverse health effects including neurotoxicity, carcinogenicity, and endocrine disruption in humans (Aktar et al., 2009). Organochlorine compounds, though banned in many countries, persist in the environment and bioaccumulate in the food chain, posing long-term health risks (Singh et al., 2018; Rajashekhar et al., 2021). Additionally, pesticide runoff contaminates water bodies, leading to the destruction of aquatic ecosystems and the loss of biodiversity. To mitigate these consequences, promoting botanical insecticides and reducing reliance on chemical pesticides is essential for ensuring sustainable rice production and safeguarding human health and the environment.
Insecticide use can have adverse effects on the ecosystem, eliminate beneficial insects, and leave residues in harvested produce. Botanical insecticides have long been marketed as appealing substitutes for synthetic chemical insecticides in pest management (Isman, 2006). Given the significance of environmentally friendly methods for managing pests, the experiment was designed to ascertain the effect of botanical extracts against the main pests of rice. Plant-based insecticides derived from a combination of five leaf extracts Azadirachta indica (neem), Vitex negundo (Indian privet), Lantana camara (lantana), Annona squamosa (custard apple), and Clerodendrum inerme (wild jasmine) have shown promising results in controlling major rice pests such as the rice stem borer, rice leaf folder and brown planthopper. These extracts possess a variety of bioactive compounds, including alkaloids, flavonoids, and terpenoids, which exhibit insecticidal, antifeedant, and growth-regulating effects on pests (SenthilNathan et al., 2006). The synergistic effect of these leaf extracts enhances pest control by disrupting the pest's physiological processes and reducing feeding and oviposition. Studies have demonstrated that foliar applications of these extracts significantly reduce pest infestation and improve rice yield without harming to beneficial insects. Garlic (Allium sativum) and chilli (Capsicum frutescens) extracts have demonstrated significant bioefficacy against major rice pests. Garlic extract, rich in organosulfur compounds such as allicin, exhibits insecticidal, antifeedant, and repellent properties that disrupt the metabolic activities of pests, leading to reduced feeding and growth inhibition (Dougoud et al., 2019). Similarly, chilli extract contains capsaicinoids, which exhibit neurotoxic and antifeedant effects, impairing pest behavior and reducing insect proliferation in rice fields (Baidoo and Mochiah, 2016). The combined application of garlic and chilli extracts enhances their insecticidal properties through synergistic effects, resulting in higher pest mortality and decreased pest infestation. Field trials have shown that foliar application of these extracts reduces pest incidence by up to 60%, improving overall rice yield and minimizing environmental contamination (Tuan et al., 2014).
Taking into account the significance of the efficacy of mixtures of plant extracts and eco-friendly approaches to pest management in the rice ecosystem, the goal of the current inquiry was to examine the effect of plant extracts on the key pest of rice.
