Diseases of Vegetables L323 



For best results in spraying at least 100 pounds pressure must 

 be used. It is usually impossible to obtain over <T>0 pounds pres- 

 sure with hand sprayers. By expending much time and labor 

 satisfactory spraying- can be done on small areas with hand spray- 

 ers, but they are out of the-question for field work. Use a horse- 

 drawn sprayer which derives power from the wheel or a gasoline 

 engine. 



GENERAL DISEASES 



Damping Off. Seedlings and weak soft plants are subject to 

 rotting off at the surface of the soil and consequent toppling over. 

 Damping off is most injurious to plants grown indoors or under 

 crowded conditions. The disease results from the attack of any 

 one of several species of fungi. 



Injury can often be largely avoided by so regulating moisture, 

 temperature, ventilation and spacing of plants as to produce as 

 stocky, vigorous plants as possible. High temperatures and an 

 excess of moisture favor the growth of the causal fungi and should 

 be avoided. Where trouble with damping off has been experi- 

 enced it may be expected that the same soil will continue to give 

 more or less trouble. This can be overcome to a large extent by 

 using new soil or by sterilizing, for which see soil sterilization. 



Root Knot or Nematode Galls. Root galls (Fig. 381), varying 

 in diameter from one-thirty-second to one-half inch, occur on a 

 great variety of plants, resulting in diminished vigor and de- 

 creased yields. They are due to the entrance into the roots from 

 the soil of microscopic worms. In this climate injury usually 

 occurs only in greenhouses, for outside the worms are largely 

 killed by the cold of winter. In badly infested houses lettuce 

 and radishes arc not appreciably injured, but the yield from 

 tomatoes is noticeably lowered and cucumbers are almost a failure. 

 Thorough steam sterilization of the soil is the only remedy that 

 can be relied on to eradicate the disease. 



ASPARAGUS 



Bust (Puccinia asparagi DC), Fig. 382. Rust is the most 

 common disease of asparagus and very destructive in some sec- 

 tions. Disease lesions do not occur on shoots cut for market but 

 older bushy tops become covered with reddish or black pustules. 



