ROOT CROP PROJECTS 



193 



13. Combating insects and diseases. — Root crops are injured 

 by insects that suck the leaf juices, eat the foliage, or mine the 

 leaves or roots. Radishes destroyed by root maggots and flea 

 beetles, or carrots injured by the carrot rust fly, are interesting 

 examples. The spinach louse (spinach aphis) is a very common 

 pest of truck crops, 

 feeding generally on a 

 number of different 

 plants in the field, or 

 in the greenhouses 

 where it may pass the 

 winter. The pinkish 

 or pale yellow soft- 

 bodied lice multiply 

 very rapidly, sucking 

 the plant juices, and 

 when abundant caus- 

 ing the leaves to curl 

 and dwarfing the 

 roots. This insect is easily destroyed by spraying with a con- 

 tact insecticide. On those crops where the leaves grow close to 

 the ground some difficulty may be experienced in applying the 

 spray. A spray boom devised for this purpose is very satisfactory 

 in field practice. 



Swarms of beet leaf hoppers often appear in fields of beets 

 through large areas of many of the western states. Beet roots 

 are subject to a disease known as curly top, which is trans- 

 mitted by these insects as they migrate from one field to 

 another. Ciu-iously enough the hoppers which travel from a 

 great distance are the most to be feared, as those which hibernate 

 in near-by fields seldom do much damage. Injuries from the 

 pests are apt to be periodical as they seem to avoid working in 

 fields which were infested during the previous season. The insect 



Fio. 51. — Swiss chard, botanically a bpet which is 

 most excellent for greens. 



