316 Diseases of Truck Crops 



Germination of the spore balls may be effected in 

 two ways: (i) the spore walls of the entire spore balls 

 break down, liberating as many amoebae as there were 

 cells within; (2) the amoebae may escape through 

 openings in the wall of the spore ball and move about 

 by means of pseudopodia. 



Control. Infected soils should never be limed, 

 since the application of lime favors the disease. 

 Rotation of crops is suggested. The land should be 

 given a rest from potatoes, or tomatoes, for at least 

 five years. Since infection of the tubers takes place 

 late, early harvesting and the growing of early 

 maturing varieties is advisable. Since the disease 

 is carried with infected seed tubers, the latter should 

 be disinfected. The use of mercuric chloride or 

 formaldehyde, or both, is recommended. (See also 

 p. 336.) No soil treatment will cure the trouble, but 

 sulphur applied at the rate of nine hundred pounds 

 per acre will reduce the amount of infection. 



Blackleg 

 Caused by Bacillus phytopthorus Appel. 



Blackleg is a dangerous disease which may readily 

 be introduced into new localities with the seed. The 

 trouble has been well described by Morse. 1 



Symptoms. Blackleg does not manifest itself until 

 the plants are about 7 to 10 inches high. Diseased 

 plants are unthrifty, undersized, with the branches 



1 Morse, W. J., Maine Agr. Expt. Sta. Bui. 174: 307-328, 1909. 



