256 HARMFUL AGENTS IN SOILS AFFECTING FERTILITY ^ 



spotted cucumber beetle. These worms are slender and yellowish- 

 white with a dark-brown head. They not only feed on the corn 

 roots, but in young corn they bore into the stems and eat the inte- 

 rior, boring out the crown, and killing the bud. Burning over waste 

 places and growing other crops on fields badly infested, thick plant- 

 ing and enriching the soil are suggested remedies. 



Root Maggot. — Some truck crops, such as cabbage, radish and 

 onions, are injured by the maggot (Fig. 161). Other crops are 

 injured by eel worms or nematodes which cause the root-knot 



Fig. 161. — Injurious work of maggot on radish. (Geneva Station, N. Y.) 



disease, as on cabbage and tomato (Fig. 162). The growing of 

 other crops has been found the most effective remedy. 



The aphis (a'fis) is a common insect which injures crops. 

 There are many species, many of which feed on the juices of plant 

 roots.^ The corn root-aphis, or root-louse, is perhaps the best 

 known. Ants are largely responsible for aphis injury to roots, 

 since they carry the eggs of these insects into the soil and care for 

 them in their nests. When the eggs hatch the ants tunnel into 

 the ground and place the helpless aphids first on the roots of cer- 

 tain weeds, such as smart weed, then on the corn roots (Fig. 163). 

 Aphids are often called ''ant cows.^' Since the corn root-aphis 



1 Cotton and asters are also commonly injured by the corn root-aphis. 



