96 FIELD CROP PRODUCTION 



corn plant, first on the small roots, then burrowing into the larger 

 ones. The root system is seriously injured if the worms are 

 plentiful, and a rain with some wind will cause the corn to blow 

 over. The worms are about one-half inch in length with a red 

 or brown head. In late summer they enter the pupa stage and 

 soon come out as adult beetles. The adult beetles are about 

 one-fourth of an inch long. The adult of the Northern corn 

 root-worm is a plain grass-green in color, while that of the South- 

 ern corn root-worm is yellowish green with twelve black spots on 

 the back. The larvae of the two species are very similar. The 

 adults feed on the corn silks in the fall, and the farmer often 

 thinks they are seriously affecting the corn, but they have done 

 all the damage they can do, except to lay their eggs which will 

 hatch the following spring. The Southern corn root-worm is not 

 common in the Northern States. The Northern corn root-worm 

 is more common and often it does considerable damage. The 

 latter is easily controlled because the larvas feed on no other 

 roots except those of the corn, so a simple rotation will starve 

 them out. In the case of the Southern corn root-worm the 

 rotation of crops will not control the insect to so great an extent, 

 because the larvffi of this species feed on the roots of other plants. 

 78. Fungous diseases. — Wherever corn is grown, corn smut 

 is found. This fungus attacks the ear, tassel, leaves, or the stalk 

 of the plant, developing at maturity into a large mass flUed with 

 small, powdery black spores. The fungus may attack the plant 

 any time after it is a couple of feet in height until it nears matur- 

 ity. The spores may remain in the field from the previous year, 

 or they may be carried there in manure or by the wind. During 

 the summer they are blown about by the wind, and fall upon the 

 growing plant. If they light upon the tender part of the plant, 

 and if moisture is present, they start to grow. Therefore the 

 tassel, silk, brace roots, and the base of the leaves afford the most 

 favorable locations for growth. The damage done each year 

 has been estimated at one or two per cent of the crop, while in a 

 year of extremely favorable conditions for it, the loss may be 

 much greater. The treatment of the seed before planting to kill 

 the spores does not greatly assist in controlling the disease, siLce 

 the spores are carried from field to field by the "wdnd. The only 

 effective means of controlling it is by going into the field several 

 times during the season and cutting off and destroying the 



