Streptomycin used for plant treatment is only partially purified, but 

 it appears to be more effective for this use than the highly purified strepto- 

 mycin of hunaan medicine. At the present time only 4 known commercial 

 streptomycin plant preparations --each containing different amounts of the 

 antibiotic--are available. They are: Acco Streptomycin, Agristrep, Agri- 

 mycin 100, all of which are dusts, and Phytomycin, which is a liquid.^ 

 Acco Streptomycin contains 45 percent streptomycin; Agristrep contains 

 37 percent; Agri-mycin 100 contains 15 percent; and Phytomycin contains 

 ZO percent. Agri-mycin 100 contains, in addition, 1.5 percent of oxytetra- 

 cycline (Terramycin) to prevent or retard the development of streptomycin- 

 resistant strains of bacteria. 



Reported here are the results of experiments in which streptomycin- - 

 in a pure form as well as in these commercial formulations --was success- 

 ful in the control of specific vegetable diseases. No attenapt is made to 

 report all of the work done with this antibiotic on these diseases, but rather 

 to present some typical results. Treatment and concentrations are not 

 presented as recomnnendations but simply to provide infornnation for those 

 interested in the potential of antibiotics for the treatment of vegetable crop 

 diseases. 



Concentrations are referred to as parts per million (p. p.m.) rather 

 than pounds per gallon, since only minute announts of the antibiotics are 

 required. A concentration of 100 p. p.m. refers to 100 parts of the active 

 antibiotic in 1 million parts of water. This is the equivalent of 38 grams 

 (about 1.34 ounces) dissolved in 100 gallons of water. Since the commer- 

 cial formulations contain inert ingredients, a greater amount of these 

 would have to be mixed with 100 gallons to obtain a concentration of 100 

 parts of the active antibiotic per million parts of water. 



DISEASES OF BEANS 



Halo Blight 



Halo blight appears wherever rain falls frequently during the growing 

 season. Only a few small areas of the Far West are free from the disease. 

 When it is widespread it can cause serious losses. 



During periods of high rainfall the causal bacterium, Pseudomonas 

 phaseolicola , causes water-soaked spots to show on the leaves, stems 

 and pods. Halo blight makes a halo-like zone of greenish-yellow tissue 

 aro\ind each water-soaked spot during cool weather. Leaves of newly 

 infected plants are yellow. As the infection advances, leaves turn brown 

 and fall off. 



Seed treatment is of doubtful value in the control of halo blight. Spray- 

 ing or dusting the plants with fungicides has not proved to be a practical 

 control measure. 



Researchers at the United States Department of Agriculture's Agri- 

 cultural Research Center, Beltsville, Md., not only controlled halo blight 

 with the antibiotic streptomycin but largely eradicated it from the treated 

 plants. It was the first time the use of an antibiotic controlled a bacterial 

 disease in a field test. 



1 Mention of these products does not constitute an endorsement by the U.S. Department of Agriculture over 

 other products or a guaranty or warranty of the standard of these products. 



