THE MONTHLY BULLETIN. 393 



the months of May, June and July, although they may sometimes he 

 found in all stages throughout the year. This uneven hatch is the 

 most common near the coast, and sometimes causes poor results from 

 fumigation, as the eggs and older scales are resistant to this form 

 of treatment. 



The young scales feed principally upon the leaves, shifting to the 

 twigs and limbs as they become larger. Injurj^ to the citrus tree by 

 this insect is principally that causecl by the sucking of the sap from 

 the trees, thereby reducing their vigor, and also on account of the 

 excretion of honej'dew, which furnishes a medium for the black smut 

 fungus. This honeydew and the fungus interfere with the leaf func- 

 tions, and also necessitate the washing of the fruit. Decay may result 

 from too-vigorous washing of the fruit, in order to remove the fungus, 

 thus increasing the damage indirectly due to this insect. This insect 

 attacks all citrus trees — the olive, apricot, grape, oleander, almond 

 and pear as well as many other trees and plants. It is best con- 

 trolled by fumigation on citrus trees. Fumigate with one-half to 

 three-fourth schedule, between September and June, at which time 

 the scales are young and are easily destroyed with hydrocyanic acid 

 gas. The one-half schedule is used when there is an even hatch, and 

 when the scales are very young. Of course, the time to fumigate 

 will depend upon the evenness of the hatching period, care being 

 taken not to fumigate while many of the scales are still in the egg 

 stage. 



Most of this fumigation is handled either by contractors, by local 

 exchanges, by associations, or sometimes by private individuals, 

 especially if the holdings are large. Sodium cyanide is now almost 

 exclusively used in fumigation work, because of the loAver cost, and 

 due to the fact that it is manufactured in this country. The formula 

 for the generation of the cyanide gas used in fumigation is as follows : 



Sodium cyanide 1 ounce 



Sulphuric acid, 66° Baume 1| fluid ounces 



Water 2 fluid ounces. 



The water is first placed in the generating jar, then the acid, and 

 later the cyanide. 



The dosage is based upon the distance around and over the tented 

 tree. To calculate the dosage for average sized trees, multiply the 

 distance around by the distance over the tented tree, point off two 

 places in the product and reduce by one-fourth. This corresponds 

 to the full schedule. For the three-fourth schedule take three-fourths 

 of this amount. 



The time of exposure is from 45 minutes to one hour. The tem- 

 perature at which fumigation is practiced is from 35 degrees F. for 

 the minimum, and 70 degrees F. for the maximum. However, it has 

 been found by Mr. R. P. Cundiff, in Tulare County, that fumigation 

 has been carried on successfully at a temperature of from 80 to 85 

 degrees.- Do not fumigate during a high wind. 



Orchards previously sprayed with Bordeaux mixture should not be 

 fumigated, as there results a chemical action which is exceedingly 

 damaging to the fruit and foliage. 



