dsRNA and RNAi
  RNA interference(RNAi) is a novel method of sequence-specifically blocking gene function that works by introducing into cells with short sequences of RNA that match part of a target organism's gene sequence.
  RNA interference works in the cytoplasm of the cell; thus it does not genetically modify the organism. It can block an organism's production of an essential protein, suppress or modify various genetic traits in an organism without changing the genetic make-up of the organism. It has been well known that long dsRNA (200-800bp) can initiate RNAi in plant, worms, insect, and even shrimp. Thus, dsRNA may be a new raw material for herbicide, insecticide, anti-fungal and anti-viral applications for agricultural as well as environmental applications. Because of its sequence specificity, it can also be designed to have no toxicity to unintended organisms.
  An RNA approach, especially when using long dsRNAs, can also minimize the development of insecticidal or herbicidal resistance, and be a key objective in the development of agricultural control agents.

  In contrast to the difficulty of delivering RNA in humans and animals, an RNAi gene silencing effect by dsRNA has been shown in plants, insects, worms, and crustaceans by a simple spray, injection, or feeding.
Even just spraying crude extracts of bacterially expressed dsRNA or in vitro transcribed dsRNA can be used to protect plants against several viral infections.
  Also a dsRNA corresponding to an essential insect gene is sprayed on a crop. As the insect is feeding on the crop, it takes up the dsRNA which in turn eliminates or reduces an essential protein in the insect leading to the death of the insect and protection of the crop plant. Another approach might be to make a dsRNA corresponding to a herbicide-resistance gene in weeds thus rendering the weed susceptible to the herbicide. dsRNAs have thus emerged as an innovative pest and weed control reagent.