290 INSECTICIDAL MATERIALS AND PRACTICES 



The top line of numbers, beginning at 16 and continuing to 78, 

 represents the distance in feet around the bottom of the tent. The 

 outer vertical columns of larger numbers running from 10 to 59 rep- 

 resent the distance in feet over the top of the tent. The number of 

 ounces of cyanide to use for a tree of known dimensions is found 

 in that square where the vertical column headed by the distance 

 around the tree intersects the horizontal line of figures correspond- 

 ing to the distance over. 



Using fungous diseases as insecticides. Fungous diseases have been 

 successfully employed against the citrus white-fly in Florida. 

 There are seven species of fungus which attack the white-fly, and 

 nearly all are more or less valuable. The object is to introduce 

 some form of the fungus into orchards and on trees where it is 

 absent. This, may be accomplished by spraying the under side 

 of the leaves with a mixture of fungus spores in water. The 

 mixture may be made by placing two or three fungus-bearing 

 leaves in a quart of water, and stirring occasionally for fifteen 

 minutes. Strain through cheesecloth, and apply to those parts of 

 the tree most badly infested with the white-fly larvse. 



The fungus may be introduced by pinning a dozen or so fungus- 

 bearing leaves to the under side of the leaves of the tree infested 

 with white-fly. The fungus-covered surface should face downward. 



Insecticidal Substances 



Arsenic. Known to chemists as arsenious acid, or white oxide of 

 arsenic. It is considered an unsafe insecticide, as its color allows 

 it to be mistaken for other substances ; but in its various com- 

 pounds it forms our best insecticides. From one to two grains, 

 or less, usually prove fatal to an adult; 30 grains will usually 

 kill a horse, 10 grains a cow ; and 1 grain, or less, is usually 

 fatal to a dog. In case of poisoning, while awaiting the arrival 

 of a physician, give emetics, and, after free vomiting, give milk 

 and eggs. Sugar and magnesia in milk is useful. 



A cheap and effective insecticide may be prepared from white 

 arsenic by the following methods : 



For use with bordeaux mixture only. Sal soda, 2 pounds; water, 

 1 gallon; arsenic, 1 pound. Mix the white arsenic into a paste, and 



