188 The Philippine Journal of Science 1932 
ful pruning also materially reduced citrus canker in all cases; 
(g) the procedure which the Japanese called “rough pruning” 
is shown to have reduced citrus canker slightly; (h) the freedom 
from canker of the fruits on plats treated by both pruning and 
spraying is such as to warrant the statement that a substantial 
control was obtained. 
TABLE 8.—The effect of the control treatnients on the presence of citrus 
canker. 
Plat Average Fruits | Fruits 
No. Treatment. Fruits. | Trees. | fruits | freeof | can- 
per tree.| canker. | kered. 
Per cent.|Per cent. 
1 | Canker removed by pruning; no spraying ----| 2,882 20 119.1 55.12 | 44.88 
2 | Cankerremoved by pruning;lime sulphur 1-40| 2, 692 21 128.1 66.59 | 33.41 
8 | Canker removed by pruning; Bordeaux mix- 2, 525 18 140.8 90.07 9. 22 
ture 4-4-50. 
4 | Canker removed by pruning; Bordeaux mix- 1, 169 16 73 93.58 6, 42 
ture, neutral. 
5 | Canker removed by pruning; Burgundy mix-| 1,712 20 85.6 | 81.48} 18.52 
ture, 
6 | No pruning; lime sulphur 1-40 -___-.---------- 2, 668 19 140.4 22.75 | 77.25 
7 | No pruning; Bordeaux mixture 4-4-50 __......| 3,389 20 169.4 62.86 | 37.14 
8 | No pruning; Bordeaux mixture, neutral _-_-.--. 2, 963 21 140.2 65.40 | 34.60 
9 | No pruning; Burgundy mixture-_-____--..------ 8, 256 20 162.8 53.40 | 46.60 
10 | No pruning; no spraying; control _..__-.-----. 4, 601 22 209.8 14.17 | 85.8 
11 | No pruning; formalin 1-100_--.....----.------- 2, 363 20| 247.1 3.86 | 96.14 
12 | No pruning; no spraying; control ---_-..-.---- 2, 487 21| 118.5], 8.25] 96.75 
13 | Rough pruning; Bordeaux mixture, neutral _- 695 9 77 70.36 | 29.64 
14 | Rough pruning; Burgundy mixture-_-----..--- 1, 224 9 186 60.38 | 89,62 
15 | Rough pruning; lime sulphur -.___--------- ne 974 10 97.4 | 61.75 | 48.25 
16 | Rough pruning; Bordeaux mixture 4-4-50__--- 1, 299 10| 129.9} 71.97] 28.03 
17 | Rough pruning; no spraying; control____-..--- 1,829 10 132.9 34,84 | 65.15 
18 | No pruning; no spraying; control _.._--.------ 2,271 18| 126.8] 19.28] 80.72 
fg Seas ee oe psa Sas prensa ta aa 524 20 26.2 7.25 | 92.75 
In a previous paper(3) the senior writer advanced the con- 
clusion, among others obtained by modifications of the phenol- 
coefficient tests, that in culture tubes copper sprays were ineffi- 
cient as bactericides for Pseudomonas citri unless the copper 
precipitant was added to excess. It is interesting to observe 
that M. and Mme. Villedieu(6) have advanced conclusions in close 
agreement with this, working upon Phytophthora infestans 
in France. The present results indicate that, although copper- 
precipitate mixtures as used in vitro in the phenol-coefficient 
tests were inefficient as bactericides, the real criterion, the tests 
as preventives in the field, indicate that they are most effective. 
These peculiar results, the failure of a neutral Bordeaux mix- 
ture to exert bactericidal action in vitro while in the field it has 
a considerable disease-preventive action, reopen the interesting 
