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Two kinds of root worms-namely the northern and southern of root worm attack corn in the United States. Most of the damage is caused by the larvae which feed on the small roots and burrow into the large roots, crowns, and stems. Root systems of infested plants are weakened to the extent that they are unable to provide the necessary water and nutrients required for normal growth. In addition, the infested plants are frequently blown over because of lack of sufficient anchorage in the soil.
The northern root worm is also referred to as the western root worm. When mature, the root worms are slender and white bodied with brownish head. The insects are about ½ inch long. The adult or beetle is pale yellowish green in color and is about ¼ inch long. Its eggs are laid in the soil where they remain over winter. The eggs hatch when the weather becomes sufficiently warm in the spring, and the young larvae feed on the roots. The northern root worm feeds only on corn. Inasmuch as this insect passes the winter in the egg stage, it is easily and effectively controlled through the use of a good rotation.
The larvae of the southern root worm are usually somewhat longer than those of the northern root worm. The southern root worms are yellowish in color and have brown heads. The beetle or adult is yellowish green in color and is marked distinctly with 12 black spots located in 4 rows on its back. It is about the same size as the northern root worm. This insect is also referred to as the spotted cucumber beetle. Unlike the northern type, however, it not only feeds on the roots of corn, but on those of other plants as well, including cucumber. It passes the winter in the adult stage. Eggs are laid in the spring on corn, other grasses, and at times on legumes. The larvae eat the smaller roots and burrow into the larger ones.
How to control root worms of insect?
Because this insect passes the winter in the adult stage and is capable of flight, rotations are not effective in its control. Winter or early spring plowing followed by late planting is a recommended means of control. Thorough cultivation before planting will destroy many of the larvae already in the soil. Because corn is usually attacked when it is young, late planting will permit the plants to escape the first generation of larvae, and in addition, this practice enables the corn to become well established and make a good growth before the next brood makes its appearance.
Broadcast applications of heptachlor or aldrin at the rate of one pound per acre immediately followed by disking to work the chemical in the top three or four inches of the soil has provided good control. The same chemicals may also be applied with the starter-fertilizer at the rate of one-half pound per acre. Farmers may mix these chemicals with the starter-fertilizer or they can purchase commercial fertilizers to which one of these insecticides has already been added.