156 The Philippine Journal of Science 1921 
tion of the untreated trees with the amounts of canker of the 
other, treated plats. 
The trees of this control plat also afford a fair idea of the 
susceptibility of the horticultural varieties represented. The 
Parson Brown, Homosassa, and Pineapple, sweet orange varieties 
of Florida origin, show a considerably greater susceptibility than 
do the Valencia, Majorca, Maltese, and Du Roi, which are 
Mediterranean varieties. The King, Suntara, and Szinkom, 
varieties of the mandarin orange, illustrate the almost entire 
freedom from canker of that class of hosts. The great 
susceptibility of the American-grown grapefruit varieties is 
illustrated by the trees of the McCarty variety in this plat. 
PLAT VII, ORCHARD B, LAMAO 
The rows of trees of this plat paralleled and were contiguous 
to those in Plat VI; treatment was as follows: 
September 4, 1917. Cresol 1-80 solution. 
September 20, 1917. Trees pruned for citrus canker. 
September 22, 1917. Lime sulphur 1-40 solution plus formalin 
1-80. 
October 22, 1917. 3-33-50 Burgundy mixture plus resin, sal-soda 
sticker. 
November 21, 1917. Formalin 1-80 solution plus powdered, neutral, 
lead arsenate to make a 1-50 mixture. 
December 1, 1917. Formalin 1-80 solution plus powdered, neutral, 
lead arsenate to make a 1-50 mixture. 
December 4, 1917. Trees pruned for twig cankers. 
December 7, 1917. Lime sulphur 1-40 solution plus formalin 1-100. 
January 10, 1918. 3-3-50 Burgundy mixture plus Yothers’s oil 
emulsion. 
January 17, 1918. Trees pruned for twig cankers. 
June 1, 1918. Lime sulphur (25° Baumé) 1-80 solution. 
June 26, 1918. 3-3-50 Burgundy mixture plus cresol-kerosene emul- 
sion and formalin 1-100. 
July 30, 1918. 3-83-50 Burgundy mixture plus cresol-kerosene 
emulsion. 
Cresol solution was used at the beginning of the work as a 
clean-up spray; however, it had no value in this respect when 
used at a dilution of 1-80 and its use was abandoned. In the 
succeeding spray applications, lime-sulphur solution was used at 
different times to check the increase of scale insects, but the plat 
was in the main sprayed with Burgundy mixture. 
Table 13 indicates that citrus canker has been materially re- 
duced in amount upon all affected varieties and species. As 
evidenced in the table, the difficulty of control of the Duncan, 
the Marsh, and the McCarty grapefruits and the Everglade and 
