20, 2 Lee and Shino: Citrus-canker Control Experiments 149 
Prefecture. For other countries, in which canker is widespread, 
a spraying schedule should be worked out to agree with the cli- 
matic peculiarities of each region. 
SUMMARY 
1. Experimental work on the prevention of citrus canker 
upon trees of the Washington navel variety of the sweet orange, 
Citrus sinensis, is described. 
2. The following results were obtained by these methods: 
Copper sprays without other treatment reduced the number of © 
fruits affected with citrus canker to as low as 34, 37, and 46 
per cent. Untreated plats had percentages of cankered fruits 
of 80, 86, 92, and 96 per cent. The cost of these spray appli- 
cations for the season was from 32.4 to 33.7 Japanese sen per 
tree. 
3. Lime sulphur without other treatment reduced canker, but 
not to such an extent as did the copper sprays. The applications 
of this spray for the season cost 31 Japanese sen, per tree. 
4, Formalin 1 to 100 solution did not reduce canker. On the 
contrary, the trees sprayed with formalin had a very slightly 
larger percentage of cankered fruits than did the controls. The 
cost of formalin sprays for the season was 1 Japanese yen per 
tree, or three times the cost of any of the other sprays. 
5. Spraying with copper sprays, accompanied by a removal 
of the sources of infection before the period of canker activity, 
reduced the canker percentage on treated plats to 9.25 per cent, 
6.5 per cent, and 18.5 per cent. The cost of such treatments was 
92 sen for Bordeaux 4—4—-50 mixture, 90 sen for neutral Bordeaux 
mixture, and 92 sen for Burgundy 3-3-50 mixture. 
6. The trees treated for the removal of sources of infection, 
without other treatment, showed a reduction to 45 per cent of 
fruits cankered, at a cost per tree of 59.6 sen. Comments show- 
ing the comparative labor efficiency in Japan and America are 
made, which show that American orchard labor is but slightly 
more expensive than Japanese, if at all. 
7. Data are presented to show that wind prevention in itself 
May reduce citrus-canker development from 50 to 60 per cent 
to 6, 20, and 37 per cent. This is also corroborated by numerous 
field observations. 
8. Data were obtained from the spraying experiments which 
Showed an increase to as high as 25 per cent of sooty mold, 63 
per cent melanose, and 100 per cent red spider following the 
copper sprays. The percentages on untreated plats were less 
than 3 for sooty mold, and 5 for melanose, and there was no red 
