Plants as Affected by Animal Parasites. 163 



fluid ounces of water. The jar is covered with burlaps 

 to prevent the rapid escape of the gas. The tent is left 

 over the tree fifteen minutes to one hour. It is advisable 

 to apply this treatment during the dormant season and 

 in a cool period. 



298. Fir-Tree Oil is considerably used in greenhouses 

 and conservatories for destroying scale insects and the 

 mealy bug.* It is mixed with warm soft water at the 

 rate of a tablespoonful of oil to a pint, and applied with 

 a syringe; or the plants are dipped into the mixture. 



299. Hot Water may also be used for destroying the 

 above-named insects (298) and plant lice (aphidre). In- 

 fested pot-plants are inverted and immersed five or six 

 seconds in a vessel containing water at 120 F. This 

 treatment must be used with caution. 



300. Insect Attacks Sometimes Become Formidable from 

 the vast number of the individuals. The chinch-bug, f 

 the army-worm J and various species of locusts or grass- 

 hoppers sometimes devastate large tracts of country. 

 For the destruction of these insects, special means must 

 be employed. 



301. The Chinch-Bug may be controlled in a measure, 

 by burning over all grass land in early spring, in seasons 

 when attacks are expected. The bugs may be kept out 

 of corn fields by plowing a furrow away from the corn, 

 on the side from which the attack is looked for, and 

 strewing stalks of fresh corn in this. As the insects 

 congregate on the corn in the furrow, they should be de- 

 stroyed with kerosene (294). Persistent and thorough 

 work is essential to success. 



* Dactylopius. f Blissus leucopterus. % Leucania unipuncta. 



