494 



CITRUS FRUITS AND THEIR CULTURE. 



Those insects which feed by biting off and chewing 

 parts of the plant can be destroyed by putting a poison- 

 ous substance on the part of the plant attacked; not 

 so with those which obtain their nourishment by sucking 

 the juices of the plant. These can only be destroyed by 

 spraying over them some penetrating or sticky substance, 

 such as kerosene emulsion, whale-oil soap or resin wash, 

 which will enter their bodies through the walls or close 

 out the air from them by plastering them under. 



Poisonous gases, liberated under tents over the trees, 

 suffocate them, and fine powders, such as pyrethrum, pre- 

 vent their breathing by stopping up their spiracles. 



7. BITING INSECTS. 



Grasshoppers, among 

 which may be mentioned 

 Rhomalea microptera Serv., 

 ScTiistocera america- 

 num Send., and Schistocera 

 obscurum Burm. Fig. 110 fre- 

 quently prove trouble- 

 some on citrus trees. 

 They feed upon the tender 

 leaves and growth, thus re- 

 ducing the foliage area of 

 the trees and lessening their 

 vigor. They most frequent- 

 ly attack the outer rows of 

 trees in the grove, those ad- 

 joining grass fields or pas- 

 tures. When they become 

 more numerous they spread 



Fig. 110. Grasshopper feeding on through the STOV6 and do 

 orange leaves. (Schistocera oft- 



Burm.) considerable damage. If 



