The introduction of the Green Revolution in the 1940s was a stepping stone in agriculture that led to high agricultural productivity and made several nations self-sufficient in food production. The Rockefeller Foundation spearheaded the revolution, thus making Mexico a self-reliant nation in wheat production by 1956 [1]. The increase in agricultural productivity is quite evident as the population grows. The farm sector has resorted to injudicious farming practices to meet global food demands and achieve higher productivity rates [2]. These include higher dependence on nitrogen fertilizers and intensive cropping practices, resulting in higher pest infestations and crop damage [2]. Insecticides are harmful substances that control insect infestations in crops and crop products. The sole aim of the insecticides has been to maximize crop yields and minimize post-harvest losses [3]. Insecticides play a significant role in safeguarding crops, ensuring sufficient food supply to the growing global population of more than 9 billion people [4]. Most of the insecticides used in agriculture are of chemical origin and contain heavy metals and sulfur. Besides chemical insecticides, organic substances such as plant extracts and metabolites have also been used as an alternative. However, most farmers prefer inorganic chemical pesticides to organic ones because of their low cost and stability, the most important of which are neonicotinoids, organophosphates, and carbamates, which account for almost all insecticidal products [5].

The use of conventional insecticides has resulted in a significant number of deaths among agricultural workers, with estimates ranging from 5000 to 20,000 per year. These pesticides are primarily toxic in nature, which has contributed to the alarming number of fatalities. The ingestion of these pesticides has been linked to several adverse health effects, including renal failure, cardiovascular disease, and respiratory problems [6]. Furthermore, the excessive utilization of these insecticides has resulted in the emergence of insect and pest resistance. The development of resistance can occur via two distinct mechanisms. Exposure to insecticides may sometimes result in the mutation of specific genes, thus leading to the development of insensitivity to the chemicals among the insects. Alternatively, insects can alter the quantity and quality of their detoxifying genes and enzymes, thus creating metabolic resistance [7]. Some insecticides may persist in the environment and accumulate in different parts of the food chain, causing widespread toxicity [8]. There is an urgent need to develop new alternatives to conventional insecticides to prevent the spread of environmental toxicity and counteract the development of insect resistance.

RNA interference (RNAi) technology has emerged as a reasonably sustainable alternative to conventional insecticides, thus balancing agricultural productivity and environmental health. This process induces instability in the messenger RNA (mRNA) and disrupts transcription and translation in specific targeted cells or organisms mediated by microRNAs (miRNAs), Small interfering RNAs (siRNAs), and Argonuate (Ago) family protein complexes. RNAi mechanism leads to disruption of gene functions and a reduction in the levels of gene products, mainly proteins [9]. RNAi has contributed significantly to advancing our insights into insect biology. The importance of RNAi in modern agriculture is clearly demonstrated by the growing number of publications in this field. The top three countries with the highest number of publications in this field are the China, the USA, and India [10]. Several attractive features of RNAi make it an efficient and responsible solution for breeders to induce varietal plant improvement rather than going for more complicated and costly procedures like CRISPR/Cas9 or TALENS. RNAi can achieve a knockdown effect (by blocking or degrading mRNA transcripts) in a gene rather than complete gene knockout. Besides their unique characteristic features of high-spread mobility inside the plant system, they can also be used as a topical formulation, thus making them a highly competitive product in the market [11]. Furthermore, the demand for these products in the agricultural field is increasing due to their sustainable approach, wherein they can induce mortality in specific target insect pests or lead to the loss of a particular function in the organism without killing them [12]. The increase in agricultural productivity has also led to large-scale insect infestations, with these insects accounting for 18%–20% of global crop loss, estimated to be worth 470 billion USD [13]. RNAi represent a potential tool to the control of crop loss and sustainably improve agricultural productivity in such a situation.

Double-stranded RNA plays a significant role in RNAi. Large-scale delivery of dsRNA can specifically target genes in insects responsible for development and overall survival [14]. Particular genes accountable for energy metabolism, digestion, internal cellular activities, chitin production, hormone balance, immunity, and insecticidal resistance can be targeted. Besides, some other target genes, primarily responsible for different molecular processes like replication, transcription, translation, and fertility, can also be considered [15]. Table 1 accounts for different knockdown targets of dsRNA delivery and their impact on insect pests.

The mechanism of RNAi in insect pests can be categorized into two main phases (Fig. 1). The first phase involves the uptake of the dsRNA by the insect cells, which is then processed by the core RNAi system. It has been demonstrated that insect cells are capable of efficiently uptaking dsRNA through clathrin-mediated endocytosis [42]. Additionally, specific proteins, such as SID-1 like proteins, RNA binding proteins (RBP), or extracellular vesicles may also facilitate the uptake process by fusing the dsRNA molecules through the plasma membrane. These molecules are also thought to play a significant role during the transfer of the silencing signal from one cell to another cell of an insect pest, thereby conferring systemic silencing [2]. Three SID1-related genes were studied in Spodoptera litura by Gong et al. [43]. Analysis using qPCR found homologoues of the SID1-like genes to be involved in the transfer of dsRNA into the cell of S. litura. In another study, qPCR analysis revealed the expression of SID1 genes in various tissues of Aphis glycines, thus implicating its important role in RNAi-based gene knockdown in the species [44]. In insects like Apis mellifera, the expression levels of the SIL gene increased upon exposure to dsRNA, thus confirming its role in RNAi. Knockdown of the SIL mRNA in Leptinotarsa decemlineata resulted in reduced RNAi efficiencies [42]. However, in certain other insects, the SID1 proteins are found to have no particular role in the process of RNAi. In a study, the silencing of three orthologs of SID1 in Tribolium castaneum had no effect on RNAi efficiency [45]. Similarly, SID1 proteins or their homologs have not been found to play any role in RNAi [46]. This suggests variable roles of the protein or its homologs in different insects. In certain insects, it may facilitate the uptake of dsRNA, while in some other insects, it may not. Once inside the cell, the dsRNA is cleaved into sRNA with the aid of the enzyme DICER. Subsequently, the sRNA is then further loaded onto specific proteins of the AGO (Argonaute) family, forming the RNA-induced silencing complex (RISC). The sRNA’s guide strand facilitates the attachment of the RISC complex to the target RNA, which results in the degradation or inhibition of translation of the target mRNA and, consequently, causes post-transcriptional gene silencing. The process primarily occurs in the cytoplasm of the insect cell.; however, it can also occur by modifying chromatin within the nucleus [47,48].

The RNAi process can be broadly classified into two types—Cell Autonomous RNAi (CAR) and Non-Cell Autonomous RNAi (NCAR) (Fig. 2). In CAR, the silencing effect of the dsRNA is limited to a single cell where it is applied [49]. In NCAR, the silencing can be further divided into environmental RNAi and systemic RNAi. Environmental RNAi involves the uptake of exogenously supplied dsRNA by cells from the environment. This can affect those particular cells that uptake it. Sometimes, the silencing effect can also pass from the primary cells that have taken up the dsRNA to secondary cells and tissues [50]. Environmental RNAi is primarily achieved in insects by feeding them the dsRNA or soaking them in a dsRNA solution. Systemic RNAi involves the delivery of dsRNA to a single healthy cell from where the silencing signal can further be spread to other cells and tissues [49]. In certain insects like red flour beetle, extracellular vesicles have been found to transport dsRNA from one cell to another, thus causing a silencing effect [51]. REXD-1, TBC-3, and SID-5 genes in C. elegans help promote systemic RNAi by transporting dsRNA intracellularly [52].

Several methods achieve delivery of dsRNA, including microinjection, ingestion, topical application, and nanoparticle delivery. Microinjection can directly apply the dsRNA to the target insect tissues or hemolymph [53]. This ensures the safe passage of the dsRNA and prevents its degradation from the harsh gut environment of the insect. However, the microinjection technique is too laborious and requires experienced personnel. It is also impossible to use the technique in the field [54].

Ingestion is one of the simplest methods for delivering dsRNA into insects and is a feasible method for field application [55]. The midgut cells can take up the dsRNA and be transported to other tissues [56]. The delivery agent is basically a liquid formulation that can be applied to the foliar parts of the plant by soaking or mixing with insect diets to facilitate their ingestion by the target insects. The dsRNA for the purpose is mostly synthesized in vitro or by certain microbes [57]. The development of transgenic plants with the ability to continuously produce dsRNA has been instrumental in inducing RNAi in insects feeding upon the plant parts. Plant chloroplasts lack RNAi machinery, thus allowing the production and accumulation of stable dsRNA [58]. Non-transgenic delivery options are less time-consuming, and cheaper as compared to the transgenic approaches. Transgenic plant development reduces the need for pesticides but faces the problem of practical application in different plants and low public acceptance [59].

Topical applications, also referred to as spray-based formulations, penetrate the cuticle of insects to cause mortality [60]. Topical applications are quite easy to use but face the drawbacks of low silencing efficiency in insects with thicker cuticles, limiting the dsRNA’s penetration [29].

Nanoparticles have been found to act as an efficient delivery vehicle for promoting the efficient uptake and stability of the dsRNA. Chitosan nanoparticles, liposomes, and cationic dendrimers have been found to prevent the degradation of dsRNA in the environment as well as inside the insect’s gut epithelium and further help in the translocation into different cells. Nanoparticles are no doubt one of the best options for the safe and efficient delivery of dsRNA, but they are too costly and may pose certain risks [61].

There have been multiple research studies to formulate different dsRNA-based insecticides specifically targeting insect pests in crops. The subsequent sub-sections deal with these insecticides’ commercial, R&D, and regulatory aspects.

Despite many uncertainties, dsRNA-based insecticides offer a number of advantages over their conventional ones (Fig. 3). Conventional insecticides are mostly inorganic in composition and can easily get transferred into the food chain as a consequence of their non-biodegradable nature and prolonger persistence in the environment. However, in this case, dsRNA-based insecticides are mostly biodegradable and non-toxic. This is due to the fact that these molecules are developed with the specific intention of targeting particular genes, thereby being specific to a particular insect pest. In comparison to their toxic inorganic counterparts, biodegradable dsRNA-based insecticides are less harmful to the environment. Inorganic insecticides poison a wide range of insects and disrupt soil ecology and fertility [89]. In contrast, dsRNA-based pesticides are natural products that can control insect infestations in crops by acting as a sustainable tool. They can be easily included under integrated pest management (IPM) strategies to confer resistance in plants or eradicate specific insect pests without harming the beneficial ones.

The RNAi technology via delivery of dsRNA faces several challenges and limitations. The stability of the dsRNA is questionable in the environment. Several environmental factors like temperature, photodegradation due to exposure to UV, microbial degradation, and wash-off due to rain may affect the stability of the molecules [90–93]. Off-target effects are another limitation of dsRNA-based insecticides. Although these insecticides are specifically designed to target a specific gene in a particular insect, sometimes, any other organism with the same sequence identity as that of the dsRNA will be affected [94–97]. In a study conducted by Pan et al. [98], dsRNA designed to target the V-ATPase gene in D. virgifera was found to induce RNAi in four other species that shared several 21 nucleotides continuous matches with the dsRNA sequence. One of the major bottlenecks in dsRNA-based insecticides is the development of resistance among the insects. Insects can bring about mutations to the target genes or to the genes involved in core RNAi machinery, thus leading to degradation of the dsRNA. Insects have been thought to bring about alterations in critical genes involved in RNAi mechanisms, thereby developing resistance that is quite impossible to mitigate. Recent studies found that D. v. virgifera and L. decemlineata developed resistance against Snf7 dsRNA and IAP dsRNA without any mutations to the dsRNA target site [99,100]. This confirms that the mutation of genes involved in the uptake and transport of dsRNA in both organisms is a potential reason behind the development of resistance. The production of dsRNA, which involves acquiring trained researchers, chemicals, and equipment, increases the cost. Increased production costs lead to increased market prices, a significant reason behind the non-acceptance of the product among marginal farmers. There is a fear amongst the common masses regarding the acceptability of dsRNA-based products similar to that of genetically modified ones. Moreover, certain industrial insecticide producers feel the onset of these next-generation bioinsecticides is a looming threat to their existing business.

The increasing global population is well substantiated by a corresponding increase in agricultural production. Large-scale use of fertilizers and deviation from proper agricultural practices have led to a rise in the population of insect pests in crops. These insects destroy crops and their products, thus accounting for substantial annual losses. Conventional insecticides have been successful to some extent in controlling these infestations. However, there has been an upsurge in resistance development in pests. Conventional chemical pesticides are also responsible for causing large-scale environmental pollution and negatively impacting certain beneficial organisms. The development of novel bioinsecticides has led to using dsRNA molecules as bioinsecticides to induce lethality among pests through the RNAi mechanism. The dsRNA-based bioinsecticides are characterized by their non-toxic, biodegradable nature and specificity. These modern-day bioinsecticides are being widely explored for sustainable pest management in agriculture. These molecules can induce mortality and target specific functions like mobility, reproduction, fertility, replication, and many other insect factors. The dsRNA molecule is sensitive to several biotic and abiotic stresses and prone to easy degradation. Several research and advancements in the field have led to the development of different methods for safely delivering these molecules and their efficient uptake within insect cells. Using dsRNA as an RNAi agent is also associated with several drawbacks related to its stability, efficiency, dosage, resistance, and off-target effects. Several research projects are being run to overcome these limitations. Few dsRNA products have been commercialized in the global market. The market penetration of such products and their acceptance is relatively slow due to the high costs involved, the need for a skilled workforce, and the fear of using genetically modified products. The stringent regulatory compliances of different countries and regions towards dsRNA-based insecticidal products hinder their commercialization. The paper advocates in favor of dsRNA-based insecticides as a sustainable tool for use in integrated pest management and highlights future research directions. Moreover, the authors emphasize the need for collaboration among industries, academics, and government bodies for efficient commercialization and acceptance of these products.