The research for new products against pathogens, parasites and infesting species, in both agriculture and medicine, implies huge and increasing scientific, industrial and economic efforts. Traditional approaches are based on random screening procedures searching for bioactive compounds. However, the success of such methodologies in most cases has been strongly limited by side-effects of the potential new drugs, especially toxicity and pharmacological resistance. The use of nucleic acids in drug development has been introduced searching for target-specific effect. In addition, a recent discovery revealed that randomly fragmented extracellular self-DNA may act as highly species-specific inhibitory product for different species, suggesting an unprecedented use of DNA for biological control. On this base, a new scenario of pharmacological applications is discussed.