In this research, the involvement of salicylic acid (SA) as a plant growth regulator and a disease protector was investigated. SA at 9 concentrations was tested for their phytotoxicity, then 4 concentrations were selected for evaluating the effect of SA on root quantity and length as well as to study its inhibitory efficacy on mycelial growth and spore germination of Colletotrichum gloeosporioides, cassava anthracnose. The results showed that four low concentrations from 50–500mg L−1 had no burns on leaf tissues. The SA at concentrations of 200mg L−1 had high root number and length as well as effectively inhibited mycelial growth and spore germination of Colletotrichum. Subsequently, SA at 200mg L−1 was tested under field conditions for two crop seasons. The plant height of SA treated-cassava was 178.36±9.65 cm in the first crop season, and the height in the second crop season at 151.41±5.55 cm, all effective when compared to the water control. For the anthracnose severity assessment, at 9months old, plants treated with SA had lower disease severity.