514 MICROBIAL DISEASES OF PLANTS. 



SOFT ROT or THE SUGAR BEET. 

 Bacterium teutlium Metcalf. 



HISTORY. A soft rot of the sugar beet, occurring in Nebraska, has 

 been described by Metcalf and Hedgcock.* 



SYMPTOMS. Beets affected with the rot show the lower half badly 

 decayed and honeycombed with "pockets" or cavities filled with a slimy, 

 stringy fluid, colorless, sour- smelling, and alive with bacteria. The 

 vascular bundles remain intact, while the tissue surrounding them is 

 usually consumed. Above ground the beets appear normal. 



METHOD or INFECTION. The germs gain entrance to the beet through 

 wounds and abrasions in the skin, and there is good reason for believing 

 that nematodes are responsible for many of the inoculations. 



CAUSAL ORGANISM. Bacterium teutlium, according to Metcalf, possesses the fol- 

 lowing characteristics: 



It is a short, non-motile rod, rounded ends, 1.5^ by 0.8/4; neither capsules nor endo- 

 spores have been observed; the organism stains readily with the aqueous stain. Gram- 

 positive. 



On nutrient agar, slow, scant, translucent, porcelain white, non-viscid, and pene- 

 trates the agar. On cane-sugar agar growth more rapid, viscid, watery, vitreous to 

 translucent, colorless. Gelatin stab, scant, filiform to beaded, dirty white, no lique- 

 faction. Cane sugar gelatin characteristic cumulus cloud appearance in stab, no 

 liquefaction. Nutrient broth slight clouding and sediment, acid produced. No 

 evidence of growth in milk. No visible growth on potato. On carrot, clear, viscid 

 and acid. On sugar beet, viscid, clear, spreading, copious, acid, parenchyma destroyed 

 leaving vascular tissue. No growth in Uschinsky's, Fermi's, Pasteur's, Fraenkel's or 

 Dunham's solution. No gas from dextrose, saccharose, etc. Facultative anaerobe. 

 No growth at 37. Optimum temperature, 17. Thermal death-point, 45. 



CONTROL. The rot is less apt to be serious if the beets are grown on 

 relatively dry soil and if rotation of crops is practiced. The selection 

 of resistant varieties seems to be the most practical solution of the problem. 



* Metcalf and Hedgcock, " A Soft Rot of the Sugar Beet," i?th Annual Report, Nebraska 

 Agr. Exp. Sta., p. 69-112, 1904. 



