E. atroseptica also causes blackleg of potato plants which is prevalent 

 during wet seasons. When the plants show rigid, rolled leaves that yellow, 

 wilt, and die, blackleg can be suspected. If tubers are produced they show 

 a soft rot which may involve the entire potato or cause a black, rotted 

 center. In either case salability is innpaired or destroyed. 



The Maine Agricultural Experiment Station found that an instant dip 

 of potato seed pieces in an Agri-mycin solution containing 100 p.p.nn. of 

 streptomycin practically eliminated seed-piece decay. On the other hand, 

 80 to 100 percent of the untreated seed pieces decayed. Treatment in- 

 creased emergence in the field, reduced the percentage of blackleg, im- 

 proved the color, size, and vigor of the plants, and increased yield by 19 

 to 72 bushels an acre. 



When cut seed pieces were treated in Phytomycin solutions containing 

 50 to 100 p.p.nn. of streptomycin, seed-piece decay was reduced and plant 

 height, number of stenns per hill, number of flower clusters per plant, and 

 yield rate were all increased. 



DISEASES OF CELERY 



Bacterial Blight 



Bacterial blight of celery, caused by Pseudomonas apii , is an im- 

 portant disease in celery seedbeds in the Everglades section of Florida. 

 The bacterium causes small, irregularly shaped spots on the leaflets which 

 change froni yellow to brown and materially lower celery grade. 



A high degree of control can be obtained with 5 applications of copper 

 A (4 pounds in 100 gallons of water), but the disease shows a tendency to 

 build up. 



The Florida Agricultural Experiment Station has reported that the 

 same number of treatments with Agri-mycin, at concentrations ranging 

 from 300 to 600 p. p.m. of streptomycin, was more effective than copper 

 A, because the severity of the disease diminished. A combination of the 

 two materials gave better control than either one separately, but not 

 significantly better than Agri-mycin. 



NEW ANTIBIOTICS 



Research is continuing to isolate new antibiotics, such as Oligomycin, 

 Griseofulvin, Filipin, Anisomycin, Mycostatin, Rimocydin,' and F-17. 

 None of these are commercially available. 



The first six of these seven antibiotics have recently been tested by 

 Agricultural Research Service scientists to determine their effectiveness 

 against fungi causing rust and anthracnose of snap and dry beans and those 

 causing downy mildew and stem anthracnose of linaa beans. Bean plants 

 were sprayed w^ith water solutions or suspensions of the six antibiotics, 

 and 24 hours later were inoculated with spore suspensions of the disease- 

 causing fungi. They were then placed in a fog chamber to provide humidity 

 favorable to infection. After 24 hours the plants were rennoved and held in 

 an open greenhouse for observation. 



2 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. 



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