December, ’20] WOGLUM AND ROUNDS: DAYLIGHT ORCHARD FUMIGATION 479 
of the tree averaged less than one-third as high as that at the point 
of greatest mortality on the sunward side. A large number of other 
trees which were similarly fumigated showed decidedly increased 
mortality on the sunward side. The scale-kill at the top of the tree 
appeared to be modified somewhat by its shape. As a general rule the 
kill at the top was noticeably superior on the part toward the sun. 
The sunward part of the top, however, was decidedly inferior to that 
nearer the bottom on the same side. While the kill at the top, sun¬ 
ward side, was superior to that of all shaded parts of the tree, there 
appeared to be no constant superiority one way or the other between 
the top and bottom on the shaded side. Illustrated by an average 
dome-shaped orange tree 12 feet tall, the highest scale-mortality in sun¬ 
shine fumigation during the winter is at the periphery of the tree in 
the direct path of the sun and about 3 to 6 feet above the ground. 
The mortality appears to decrease in all directions from this point and 
is lowest on the shaded north side, which is least influenced by tem¬ 
perature changes. The scale-kill in sunshine work at any time at 
best must be very irregular since it is influenced directly by tempera¬ 
ture and this varies in different parts of the tree. Furthermore, the 
ratio of the temperatures at different parts of a tented tree to each 
other changes with the position of the sun at different hours of the 
day as well as its angle to the horizon at different seasons of the year. 
The Influence of Tenting Material 
Eight-ounce special U. S. army duck is considered the most satis¬ 
factory gas-holding cloth used in commercial fumigation, and tests 
by the senior writer have demonstrated its superiority to drills in 
night fumigation. Tents are frequently dipped in tannin to prevent 
mildew but it has been determined by experimental night fumigation 
that this in no way increases their gas-holding quality. Therefore, it 
was a matter of considerable surprise to ascertain superior kill in sun¬ 
shine fumigation with tannin-treated drill tents than with eight-ounce 
army duck. 
Table III —Showing Comparative Scale-Kill from Sunshine Fumigation with Liquid Hydro¬ 
cyanic Acid Under Tannin-Treated 6§-Ounce Drill and Untreated 8-Ounce Duck Tents. 
Immature Black Scale. Full Schedule. Exposure 50 Minutes. Outside Temperature 
68°—70°, March, 1920 
No. trees 
Per cent killed 
Shade (N.) 
1-3 ft. 
Sun (S.) 
2-6 ft. 
Top 
Tannin-treated drill. 
2 
3 
99.3 
92.7 
99.6 
99.5 
99.2 
97.7 
White duck. 
