64 FUMIGATION INVESTIGATIONS IN CALIFOENIA, 



Second. — An economy of cyanid results from the accurate measure- 

 ment of the water. Three parts of water are always used, resulting 

 in the maximum amount of available gas for practical work, as already 

 explained (pp. 38-39). Under the old system the water is usually 

 measured with an ungraduated di]:)per at the tree, and as the cyanid 

 and acid have been previously measured out into small cans, which 

 are in turn placed on a tray to be carried from tree to tree, the sched- 

 ule is not carried along for consultation in estimating the water, but 

 the required amount of water is guessed at from the amount of chem- 

 icals in the cans intended for that particular tree. Owing to the vari- 

 ation in the proportion of water which results in this way, the maxi- 

 mum amount of available gas is seldom produced by the reaction. 



Third. — By the old method the cans on a tray sometimes become 

 confused, in consequence of which some trees get the dosage measured 

 out for others. This error is eliminated under the improved system, 

 as the dosage for each tree is measured out just before that particu- 

 lar tree is fumigated. 



Fourth. — The tent pullers seldom get more than one or two trees 

 ahead of the cart. As a result, all trees receive the same length of 

 exposure. Under the old system, when the tent pullers got far ahead 

 of the cart at the end of a row, these trees received a much shorter 

 exposure than the first trees. 



DOSAGE SCHEDULE. 



Having obtained the dimensions of the tented tree, the next step 

 is to determine the dosage. It has been previously stated that the 

 cubic contents can be calculated from these two dimensions. Tliis 

 might be done in the field and the trees then dosed in pro]:iortion to 

 the contents. The time required f(n' the calculation of the dosage, 

 however, even after determining the cubic contents of the tree, would 

 not only prevent ra])id field work ami allow an opportunity for error, 

 but would cause a lack of uniformity in dosage, from the consideration 

 of the cubic contents alone, as will be explained later. This diffi- 

 cult}' has been obviated by preparing a dosage schedule from which 

 the required dosage may be learned without any figuring as soon as 

 the measurements of the tree are known. 



The orchardists in the citrus section about Whittier, Cal., desired 

 to commence fumigating for the jiurple scale during the latter part 

 of July. The question immediately arose as to what dosage could be 

 used at that time of the year without injuring the young fruit. As 

 stated under experiment No. 4 (p. 52), while the fruit is small a dosage 

 of 1 ounce to 100 cubic feet could be used on trees from about 10 to 15 

 feet in height without injury to the fruit, whereas smaller trees 

 would stand a heavier dosage. As this was the limit of dosage which 



