It is now reserved mainly for control of fire blight on pears. The reason for the decreased use is that there is a possibility that the streptomycin might buildup in the human body. The concern was that when streptomycin was needed for medical purposes, the body would have a resistance built up and the medical streptomycin would not be as affective.
In place of the agricultural streptomycin, fixed coppers should be considered.
— Special thanks to Dr Jerral Johnson, Professor Emeritus
Dept Plant Pathology and Microbiology, Texas A&M University