ROTS. 513 



SOFT ROT OF MUSKMELOM. 

 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 investiga- 

 tion of the cause of the touble 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 follow- 

 ing characteristics: 



A bacillus i.ofj. to 1.7^ by 0.6 fj. to o.gjj. actively motile by 4 to 6 peritrichiate flagella 

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



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

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

 opalescent growth having umbilicate elevation. Gelatin stab, infundibuliform lique- 

 faction in two days. Cooked potato, abundant, spreading, glistening, odor of decay- 

 ing potatoes. Litmus milk, coagulated and reddened in three days, no digestion. 

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

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

 melon, citron, carrot, potato, beefj" and turnip. Giowth and some acid but no gas 

 from lactose, etc. Slight gas production from asparagin broth, abundant in fermen- 

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

 from nutrient broth and potato. Nitrates reduced. Slight indol. Ammonia 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 preventative measure. 



The melons should be supported by some means to keep them from 

 coming in direct contact with the soil, and should be supplied with 

 adequate water during a dry season to keep them from cracking. 



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



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



33 



