In field tests, lima bean plots sprayed v/ith Agri-mycin containing 

 50 p. p.m. of streptomycin and the same amount of copper showed only 

 about 6 percent of the pods infected, connpared with 30 percent in the un- 

 treated plots. ARS scientists believe that a slightly higher antibiotic con- 

 centration and better plant coverage would have resulted in even less in- 

 fection in the treated plots. 



DISEASES OF TOMATOES 



Late Blight 



Late blight of tonnatoes is caused by the fungus , Phytophthora infestans , 

 which also causes late blight in potatoes. Prevalent during wet weather, it 

 may appear in nnost of the comnnercial tonnato-growing sections of the 

 United States. Increased use of fungicides in recent years has greatly re- 

 duced loss from this tomato blight. 



Agristrep, Agri-mycin, and Phytomycin sprays effectively protected 

 tomato seedlings from late blight in greenhouse tests at the Agricultural 

 Research Center. Eight-inch tomato seedlings sprayed with any of these 

 commercial formulations at concentrations of 100 p. p.m. of streptomycin 

 and inoculated with the tomato blight organisms 24 hours later remained 

 almost totally free of the disease. Untreated plants were severely in- 

 fected. Later inoculations without further treatment might well have in- 

 fected the plants. 



Bacterial Spot 



One of the common diseases of tomatoes is bacterial spot, caused by 

 the bacterium, Xanthomonas vesicatoria . It is most prevalent in the Middle 

 Atlantic, South Atlantic, and Central States. The disease attacks both 

 leaves and fruit, and results in substantial yield reductions. Various 

 fungicides are used to combat it. 



Control of bacterial spot with streptomycin in tomato plant beds and 

 in connmercial fields has been reported by the Florida Agricultural Experi- 

 ment Station. In beds treated with an Agri-mycin spray containing 200 

 p. p.m. of streptomycin, 95 percent of the plants were suitable for trans- 

 planting as compared with only 27 percent of those in the untreated beds. 

 Five sprays were applied at intervals of 2 to 4 days. 



In tests with mature infected plants, which were sprayed when they 

 were setting fruit, treated plots gave 42 percent greater yield, 28 percent 

 greater average fruit size, and 11 percent greater number of fruits than 

 untreated plots. Other tests, which included 7 applications, at 4 to 5 day 

 intervals, of Agri-mycin at a concentration of 200 p. p.m. of streptomycin, 

 and begun when the plants were 4 inches high, resulted in fewer infected 

 plants and increased yield over untreated plots. 



DISEASES OF PEPPERS 



Bacterial Spot 



Peppers are attacked by the same organisnn causing bacterial spot of 

 tonnatoes. At the Delaware Agricultural Experiment Station, 3 spray ap- 

 plications of streptomycin at a concentration of 500 p. p.m. eradicated the 



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