278 FORAGE PLANTS AND THEIR CULTURE 



the young larva feeds on the juices of the developing ovary, 

 preventing the formation of the seed. If a head of 

 sorghum be bagged before it blooms so as to exclude the 

 insect all of the seeds may develop. The insect also lives 

 in Setaria glauca, Tridens flava (Sieglingia seslerioides) 

 and probably other grasses. Its occurrence is probably 

 general in the Southern States over about the same area 

 as cotton. 



Corn-worm ( Helioihis armiger) . The larva of the corn- 

 worm is often found in the heads of sorghum, but mostly 

 in those which are rather dense. 



Chinch-bug (Blissus leucopterus). Chinch-bugs, when 

 abundant, do serious damage to young sorghum plants. 



Fall army-worm (Laphygma frugiperda). The fall 

 army-worm, when abundant, may do serious damage to 

 sorghums. The larvae usually feed in the young leaves 

 while still coiled, perforating them so that they may break 

 off after they have expanded. Sometimes the larvae 

 tunnel into the young stem below the developing head, 

 which may later break where weakened. 



Sorghum aphis (Sipha flava). This plant louse is 

 sometimes abundant, but rarely does much damage. 



334. Sorghum improvement. The improvement of 

 sorghums by breeding presents no particular difficulties, 

 but care is necessary to keep any strain pure. Sorghum, 

 like corn, is wind pollinated, and different varieties grown 

 close together cross freely. Uncontaminated seed can 

 easily be obtained by bagging the heads before the stigmas 

 are exposed. After the seeds have set, the bags should 

 be opened to prevent molding. Natural crosses may be 

 found in almost any field of sorghum. Heterozygote 

 plants are often prominent from the fact that they grow 

 much taller than the other plants. Artificial crosses are 



