40 FUMIGATION FOR THE CITRUS WHITE FLY. 



the same as the surface area of such a figure, but rather the area of a 

 circle witli a diameter eciual to the distance over the top of the tent 

 from ground to ground. To a certain extent the folds in a tent when 

 in position over a tree reduce this surface, but this is a factor of little 

 consequence, as it is present in all cases, and the portion of the tent 

 folded so as to prevent all leakage represents only a small percentage of 

 the whole. For practical purposes, therefore, the leakage surface is 

 calculated from the mathematical formula 3.1416 multiplied by the 

 square of the radius or tiR^. The approximate height of the tented 

 tree can be calculated from the following formula, in which C repre- 

 sents the circumference of the tent at the base and O represents the 



.u . XT C/;r O-C/2 

 distance over the top : ti= ^ + — -^ 



The diameter is found by dividing the circumference by 3.1416. 

 The height and diameter having been obtained, the cubic contents of 

 the regular figure mentioned can be calculated by the following for- 

 mula : 7rR2 ( H — ^ )• The actual cubic inclosure of a tented tree will 



obviously always be more or less smaller than the regular figure to 

 which this formula applies, although irregularities in shape will have 

 a tendency to counteract one another. 



DOSAGE REQUIREMENTS FOR THE WHITE FLY, 

 EXPERIMENTS WITH SHEET TENT. 



Summary of results with regard to dosage. — In experiments to 

 determine the dosage requirements for the white fly when using 

 sheet tents, detailed records were made concerning each tree fumi- 

 gated during the first season's work," including every factor which 

 might influence the results. The main objects in view in conducting 

 the experiments were to determine the minimum dosage require- 

 ments for destroying the white fly larvae and pupie, the rate of leakage 

 of the gas through the cloth, the effect of moisture on efficiency of the 

 treatment, the effect of the treatment upon the foliage under various 

 conditions of moisture, the margin as to dosage between effective 

 treatment for the insect and danger to the tree, and the effect of 

 different proportions of water and acid. Observations on other 

 points, such as effect of wind, sunlight, condition of foliage as 

 affected by drought, etc., were made as opportunity afforded. All 

 the experiments were conducted between January 12 and March 

 1, 1907, inclusive, but observations as to results were continued for 

 several weeks after the latter date. During this period practically 



« The results of the experimental work during the winter of 1907-8 substantiate the 

 conclusions derived from the work of the first so^ason so far as the data up to this time 

 completed show. 



