130 The Philippine Journal of Science 1921 
The writer wishes this paper to be considered as merely a 
progress report, since past work has been of value mainly in 
indicating the great differences in susceptibility of the commer- 
cial Citrus species and varieties and the differences in effort 
necessary for the control of canker on such different species 
and varieties. Such methods of control as have been success- 
ful to some extent are also reported here. 
DISTRIBUTION OF CANKER IN THE PHILIPPINES 
The citrus industry in the Philippines consists for the most 
part in the production of mandarin oranges (Citrus nobilis) from 
seedling trees; a few seedling sweet-orange trees (Citrus 
sinensis) , a few pummelo trees (Citrus maxima ) , and calamondin 
(Citrus mitis) trees are also grown. The largest center of 
production of citrus fruits is Batangas Province, south of Manila. 
In some of the outlying islands citrus canker has not been 
found, as yet, which has given rise to the suggestion of Mackie 
( 14 ) that canker has not existed in the Philippines for a great 
period of time. Although Wester (20) has shown the presence 
of citrus canker in the isolated Batanes (the small islands lying 
between Luzon and Formosa) as early as 1909, he has found it 
to be entirely absent from certain regions of Mindanao and 
Sulu Archipelago. This, then, would corroborate the sugges- 
tion of Mackie. For the purpose of this paper, in any case, 
it is sufficient to note that canker is distributed throughout 
Batangas and Laguna Provinces and the citrus plantings of 
the Manila Bay region where the experiments were carried on. 
The main control work was begun at two places; in the 
orchards of the Lamao agricultural experiment station of the 
Philippine Bureau of Agriculture, and in the citrus plantings, 
in Los Banos, of the College of Agriculture of the University 
of the Philippines. Control work was not attempted on the 
plantings of private holders since they consisted for the most 
part of mandarin orange trees which are in most cases resistant 
to citrus canker. 
CLIMATIC CONDITIONS OF THE REGION SURROUNDING MANILA 
An understanding of the climatic conditions at Lamao and 
Los Banos is essential before undertaking a discussion of the 
control work. 
Briefly, at Lamao and Los Banos, the year is divided into two 
seasons ; the wet season, beginning generally about the middle of 
May and ending in November, and the dry season, beginning the 
latter part of November or early December and lasting until the 
