**1. Crop protection and RNAi**

The beginning of human civilization can be traced back to the ability of cultivating crops. This has allowed that a higher number of people could be supported in the same environment; however, it also brought several crop protection challenges that mankind has been facing continuously. To ensure sufficient food production, since the earliest days of agriculture, farmers

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have had a history of using agrochemicals to protect their crops against yield loss from a vast range of organisms including pest insects, mites, fungi, weeds, and others.

The modern era of synthetic pesticides began in the 1930s, and with insects, fungal pathogens, and weeds, destroying each one more than 13% before harvest and about 10% in postharvest [1], the pesticide use has become fundamental to modern crop protection technology. The increasing resistance [2] of weeds, pest insects, and fungi to established agrochemical compound classes, stringent regulatory environment rules, and market growth has stimulated demand for more selective, safer, and cost-effective pest control methods. Crop protection scientists have allocated a great deal of intellectual energy into seeking of more refined strategies to reduce crop losses such as transgenic crops expressing *Bacillus thuringiensis* (Bt) [3] toxins and more recently gene silencing through RNAi (RNA interference) [4, 5].

RNAi is a natural process present in eukaryotic cells for gene regulation and antiviral defense. Although, from a crop protection perspective, RNAi refers to double-stranded RNA (dsRNA) mediated gene silencing that involves the blocking of the expression of specific target genes by- destroying the corresponding mRNA molecules affecting only the translation process. Due to- its sequence-dependent mode of action, the RNAi technology, as referred nowadays by industry, has a vast range of potential crop protection application, including genetic studies and pest control research in insects [6–12], mites [13–15] and ticks [16], plant pathogens [17–23], termites, nematodes, and weeds [2, 24, 25] in a range of crops. These RNAi practical applications have been pursuing over the last decade for the development of novel crop protection methods.

The application of this technology did not go unnoticed in agriculture; hence, since the discovery of RNAi and its regulatory potentials, it has become evident that RNAi has immense potential in opening a new vista for crop protection. Nevertheless, one of the biggest challenges for the RNAi technology is to make possible that target organisms (i.e., pest insects, plant pathogens, nematodes, viruses) uptake intact and active molecules that will trigger an RNAi pathway. Delivery of dsRNA to a target organism is the easiest through transformative RNAi approach (i.e., transgenic plants) [26, 27], but it is not practical to every target and crop. Therefore, the development of nontransformative approach (i.e., sprayable dsRNA) [9, 11, 28] for RNAi delivery will boost up its use in the field.-
