NS-83 is prepared from a kind of the decomposed plant material and is effective in the induction of tolerance to the infection of plant viruses such as TMV, PVY, PVX, CMV, TuMV, and so on. It strongly inactivates and inhibits viruses in vitro, while partially inhibits virus multiplication and spread in vivo. It has been demonstrated that NS-83 induces the increase of activity level of enzymes such as peroxidase and its isoenzymes, phenylalanine ammonia-lyase (PAL) and cytokinins which are usually correlated to some extend with the degree of tolerance of plants to virus infection. Besides, the NS-83-treated plants are also induced to produce pathogenesis-related proteins (PRs). In field tests, NS-83 shows the inducing effect on the decrease of severity of symptom expression, promotion of plant growth as well as improvement of the quality of plant products, therefore, resulting in the increase of yield. It influences the probing habit of aphid vectors and therefore reduces the rate of virus transmission. NS-83 is prepared from a kind of the decomposed plant material and is effective in the induction of tolerance to the infection of plant viruses such as TMV, PVY, PVX, CMV, TuMV, and so on. It strongly inactivates and inhibits viruses in In vitro, while partially inhibits virus multiplication and spread in vivo. It has been demonstrated that NS-83 induces the increase of activity levels of enzymes such as peroxidase and its isoenzymes, phenylalanine ammonia-lyase (PAL) and cytokinins which are usually correlated to some extend with the degree of tolerance of plants to virus infection. Besides, the NS-83-treated plants are also induced to produce pathogenesis-related proteins (PRs). In field tests, NS-83 shows the inducing effect on the decrease of severity of symptom expression, promotion of plant growth as well as improvement of the quality of plant products, therefore, resulting in the increase of yield. It influences the probing habit of aphid vectors and therefore reduces the rate of vi rus transmission.