FUMIGATION OF CITRUS TREES. 13 



necessary in the purchasing of a fumigation outfit usually is better 

 satisfied if he has exercised, or had the opportunity to exercise, his 

 own judgment in the selection of the cloth, even if experience has 

 proved one particular kind to be superior to all others. To satisfy 

 this demand of independent people it is suggested that anyone con- 

 templating the purchase of a fumigation outfit procure as many 

 samples as possible of 6^-ounce to 8-ounce drills and 8-ounce ducks 

 and compare the tightness of these samples with that of samples of 

 the 7-ounce and 8-ounce special drills recommended by this investi- 

 gation. This can be done by holding the various samples at different 

 angles between the eye and the sun, noting the comparative number 

 of light rays penetrating the different samples. 



Construction. — In California the demand for fumigation tents is so 

 great that several concerns make a special business of meeting it. 

 The man contemplating the purchase of an outfit visits one or all of 

 these different dealers, and, having selected the cloth which meets 

 with his approval, places his order for the number of tents of the 

 size desired. These are shipped to him ready for use. A method of 

 constructing tents will be explained, however, for the benefit of 

 people more distant from the sources of supply than are the people 

 of southern California. As .previously explained, the tents are flat 

 sheets, octagonal in shape. The ducks and drills are usually 30 

 inches wide, although sometimes they measure 29 or 29 J inches. 

 The sides of the strips are sewed together so that the strips all run 

 in a parallel direction. Before attempting to cut the cloth for a 

 tent it is well to construct a diagram having therein an exact rep- 

 resentation of the number of strips required as well as their length and 

 shape. Such a diagram is shown in figure 2 (p. 14), and was originally 

 presented by Dr. A. W. Morrill, 1 who was engaged in fumigation 

 work against citrus pests in Florida from 1907 to 1909. Each side 

 of the tent or octagon, when constructed, will be equal, approximately, 

 to two-fifths of the distance between the parallel sides. In explaining 

 the construction Dr. Morrill states: 



The strips when cut should be overlapped three-eighths or one-half inch and double 

 stitched, and all raw edges should be hemmed. In calculating the number and 

 length of strips the overlapping will reduce the width of the cloth from three-fourths 

 inch to 1 inch. As an illustration of the method of calculating the length of the 

 strips used in making an octagonal tent of 8-ounce duck, 50 feet may be taken as the 

 desired size. This is equal to 600 inches and the width of the cloth , if 29.5 inches, 

 will be reduced to 28.5 if overlapped one-half inch at the seams. By dividing 28.5 

 inches into 600 inches the nearest multiple is found to be 598.5 inches, or 49 feet 

 10 1 inches, which is sufficiently close to the desired width for practical purposes. 

 The number of strips in a tent 598.5 inches wide is 21. The middle section B [fig. 2] 

 is approximately two-fifths the entire width, or 239.5 inches. Deducting this from 

 598.5 inches, the entire width, the remainder, 359, equals the sum of the widths of 

 sections A and C. These sections being equal, the width of each is 179.5 inches. 



1 Bui. 76, Bur. Ent., U. S. Dept. Agr., p. 16, 1908. 



