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Lee: Citrus-canker Control 
157 
the Trinidad limes is noteworthy. This can be compared with 
the relative freedom from canker and ease and quickness of 
control of the Mediterranean sweet orange varieties, the Du Roi 
and Hart’s Late. 
Plat VIII, in Orchard B, yielded much the same conclusion and 
need not be presented in detail here. In this plat the Paper 
Rind and the Maltese, varieties of the sweet orange, showed 
slight susceptibility and responded readily to the control 
measures. These varieties are of interest since they are usually 
also classed with the Mediterranean group of sweet-orange 
varieties. 
DISCUSSION OF METHODS AND RESULTS AT LAMAO 
From the foregoing it is apparent that canker has been re- 
duced in the treated plats to a degree at which it may be said 
that a reasonable control has been obtained. Untreated plats 
have shown no reduction in canker. Of course, the number of 
spray applications must be considered, ten fungicide applications 
having been made on those plats and a considerable expenditure 
of labor incurred in pruning. Although such procedure would 
immediately appear prohibitive as an orchard practice, to arrive 
at the correct conclusion as to its feasibility consideration must 
be taken of the different citrus species as hosts, of the different 
degrees of their susceptibility and the bearing such susceptibility 
has upon the ease or difficulty of control, and of the cost of con- 
trol. The spray applications and other methods used on these 
plats sufficed to decrease the amounts of canker, to a degree that 
could be considered a control, upon the most susceptible hosts, 
the lime and grapefruit varieties, as well as upon the more 
moderately susceptible hosts. Upon less susceptible hosts, such 
as the sweet orange, the lemon, and the mandarin orange, these 
control measures apparently could be much simplified and, 
consequently, of course be made cheaper. 
The correct conclusion from these experiments would seem to 
be that control has been obtained, but that upon the grapefruit 
and limes such control is not economically feasible by the methods 
employed ; upon the less susceptible hosts control has also been 
obtained, though the treatments applied apparently exceeded 
actual requirements for the efficient control of canker. There- 
fore, no conclusions as to the practicability of control upon such 
hosts can be drawn as yet. Further experiments are now in 
progress to make possible definite conclusions on the control of 
such moderately susceptible hosts. 
