FUMIGATION OF CITRUS TREES. 37 



Having determined this, the dosage strength to use must next be 

 learned. On this latter point the writer has spent much time, and 

 elsewhere in this bulletin will be found information as to what dosages 

 should be used for most of the common scale pests. 



PROCEDURE. 



Five men are required to operate this system to advantage. Two 

 men pull the tents and kick in the edges around the bottom of the 

 tree. One man takes the measurements of the tree, and should also 

 empty the generator to be used for that tree and have it in readiness 

 by the time the supply cart arrives. He should empty the generator 

 with one and the same hand at all times, and with this hand he should 

 never touch the tent. He should also be careful not to slop any of the 

 residue on his clothes or shoes lest it be rubbed off on the tent and thus 

 produce acid holes. The supply cart, described on pages 22-23, is most 

 convenient for carrying the chemicals from tree to tree. Two men 

 look after the chemicals — one measures the water and acid, the other 

 weighs the cyanid. The latter then holds up the edge of the tent while 

 the acid man places the charge beneath the tree. (See PI. VIII, 

 fig. 2.) 



Ill actual field practice, after the tent-pullers have commenced 

 removing the tents the cart is brought to one end of the row which 

 is to be fumigated. (See PL VIII, fig. 1.) The estimator secures 

 his measurements and calls them out 'to the cyanid weigher at the rear 

 of the cart, who then determines the dosage from a schedule which is 

 fastened to the raised platform. The required amount of chemicals 

 is then measured and the tree dosed. While the handlers of cyanid 

 and acid are thus engaged the estimator has moved on to the next 

 tree, secured his measurements, and holds his generator in readiness 

 when the cart is brought up. This tree is dosed in the same manner 

 as the first, and thus the procedure continues until the entire row has 

 been fumigated. 



The above procedure is such as the writer has used in the field and 

 as has been followed by most outfits using the improved system. 

 In the procedures adopted by some other outfits there are marked 

 differences in the duties of the different men. 



ADVANTAGES UNDER THIS SYSTEM. 



This improved system possesses decided advantages over all 

 others. The element of guess in estimating dosage and the conse- 

 quent waste of cyanid under the old method are eliminated. With 

 the use of a known dosage strength certain definite and uniform 

 results occur. The chemicals are measured accurately and the most 

 economical proportion used at all times. Each tree gets the dosage 

 scheduled for it — a result which did not always happen under the 

 old method, owing to confusion of the cans on the tray. The tent- 



