986 MICROBIAL DISEASES OF PLANTS 



SOFT ROT or MUSKMELON 



Bacillus melonis Giddings 



HISTORY. Toward the close of the season of 1907 the muskmelons 

 in certain sections of Vermont were attacked by a soft rot. An 

 investigation of the cause of the trouble by Giddings* showed it to be 

 due to a microorganism which he has called B. melonis. 



SYMPTOMS. The decay usually begins on that part of the melon 

 next to the soil as shown by the shrunken but generally unbroken skin 

 over the soft diseased area. There is a complete collapse of the melons 

 accompanied by some frothing and a disagreeable odor in the last stages. 

 A microscopic examination of the diseased tissue, both fresh and killed, 

 shows that the bacterial invasion is purely intercellular, and the patho- 

 logical condition of the tissue manifested as a soft rot is due to the 

 solution of the middle lamellae. 



Infection in the field appears to take place through wounds in the 

 skin, and especially through cracks in the skin and flesh. 



CAUSAL ORGANISM. According to Giddings, Bacillus melonis possesses the 

 following characteristics: 



A bacillus i.o/x to i.jjj. by o.6ju to o.gn, actively motile by 4 to 6 peritrichate 

 flagella. Endospores not produced. Gram-negative. Stains readily with aqueous 

 stains. 



In nutrient broth, strong clouding twenty-four hours, neither pellicle nor ring k 

 slight sediment. Agar stroke, abundant, contoured, shiny, glistening, without color, 

 opalescent growth having umbilicate elevation. Gelatin stab, infundibuliform 

 liquefaction in two days. Cooked potato, abundant, spreading, glistening, odor of 

 decaying potatoes. Litmus milk, coagulated and reddened in three days, no di- 

 gestion. No growth in Cohn's solution. Abundant growth in Uschinsky's solution, 

 ring, pellicle and heavy sediment, odor of hydrogen sulphide. Vegetables rotted 

 muskmelon, citron, carrot, potato, beetf and turnip. Growth and some acid but 

 no gas from lactose, etc. Slight gas production from asparagin broth, abundant in 

 fermentation tubes of milk, this gas being 99 per cent carbon dioxide. Hydrogen 

 sulphide from nutrient broth and potato. Nitrates reduced. Slight indol. Am- 

 monia from asparagin broth; none from broth, gelatin, milk or urea. Thermal 

 death-point, 49 to 50. Optimum temperature, 30. 



CONTROL. Spraying with Bordeaux mixture or other fungicides is 

 recommended as a preventive measure. 



* Giddings, Bull. 148, Vermont Exp. Station. 1910. 



f B. carotovorus, Jones, associated with several soft rots, does not rot the beet. 



