CORN LEAF APHIS 201 



INSECTS ATTACKING BEETS 



The Beet Aphis. This louse (Pemphigus betce Doane) is 

 found in clusters on the small rootlets of the sugar beet, and is 

 very destructive in some of the Pacific Coast states. Infested 

 beet plants fail to make normal growth, and the beets become soft 

 and spongy. Small rootlets are attacked, cutting off the plant 

 food supply. A plant badly infested indicates its condition by 

 wilting of the leaves, and if the plants are small they may die as 

 a result of the attack. 



Life History. Several generations occur in a season, and wdnged 

 individuals appear from time to time. These winged forms are 

 usually found in the fall, at which time they fly to cottonwood 

 trees and give rise to true sexual forms. After mating, the female 

 deposits a single winter egg in a crevice of the cottonwood bark. 

 In the spring this egg gives rise to a louse, which forms a gall on 

 the cottonwood. A single generation of lice are produced in the 

 galls. These are all winged and migrate to beets, weeds, and 

 grasses, there giving birth to young, which descend to the roots 

 and start new colonies of winged viviparous females. 



Control. But few measures of control are known. Scientific 

 rotation of crops is advised, and it is suggested that root crops be 

 not grown on the same land year after year. 



INSECTS AFFECTING CORN AND SUGAR CANE 



A number of insects affecting the corn crop are treated under 

 other heads. The corn ear-worm eats into bolls of cotton and 

 is called also the cotton boll worm. (See page 218.) It also 

 bores into the fruit of tomato, and attacks corn in the silk. The 

 chinch bug is a serious enemy of corn, wheat, and other crops. 

 (See page 191.) 



The Corn Leaf Aphis. This plant louse (Aphis maidis Fitch), 

 like most others of the family, has both winged and wingless 

 forms. The wingless lice are pale green in color, and the winged 

 lice are black and green (Fig. 217). They appear in midsummer, 

 at which time they may be found on young corn leaves, where 

 they continue until cold weather. 



Injury. This insect is rarely injurious, but heavily infested 

 leaves turn yellow or red and may shrivel and die, especially in 

 dry weather. 



Control. Numbers of insect parasites help to control it under 

 normal conditions, 



