Jan. 1908,] 



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Plant Sanitation. 



well as the husks or shells of healthy pods, should be buried, and it has further 

 beeu advised that all dead fruits from the cacao tree, whether diseased or not, 

 should be systematically collected, and included in the general burial (Agricultural 

 News, Vol. VI, p. 174). "Where such methods have been adopted, considerable 

 prevention of " pod disease " has undoubtedly resulted. 



Investigation into the disease affecting the coconut palm in Trinidad has 

 also emphasized the necessity of keeping plantations as free as possible from dead 

 or diseased trees, and it would appear that wherever careful sanitary methods 

 have been adopted, the spread of the diseases has been considerably checked. 

 Many other diseases might be instanced under this heading, but it is only necessary 

 to direct the attention of planters to " canker," " die back," and " thread " disease 

 of cacao; "anthracose" of cotton; and " root disease " of sugar-cane, as instances 

 of diseases that can be controlled with fair success by care in cultural operations. 

 Canker of cacao is caused by a wound parasite, and makes itself the more noticeable 

 on such estates where pruning is not carefully carried out. As much "canker," 

 "die back," and " thread'blight" as possible should be cut out during pruning 

 operations, and portions of estates that are at all badly affected should receive 

 special attention. " Anthracnose " of cotton may be induced somewhat by too 

 close planting, whereas the "root disease" of sugar-cane can be prevented, to a 

 certain extent, by care in cultivation, and in the treatment of cane cuttings as 

 recommended by the Imperial Department of Agriculture. 



(2) For the destruction of fungus parasites without injuring the host-plant, 

 the disinfection of cotton seed in corrosive sublimate may be taken as an example. 

 Spores of "anthracnose" have frequently been observed in the lint that remains 

 attached to the seeds after ginning. Theje, if allowed to remain, might cause loss 

 amongst the cotton in the seedling stage, but as recommended by the Imperial 

 Department of Agriculture, they can be efficiently destroyed without damaging the 

 germinating power of the seed, by soaking in a one-part-per- thousand solution of 

 corrosive sublimate for twenty minutes. It might also be suggested that similar dis- 

 infection might be successfully adopted in respect to other seeds of economic value, at 

 the time they are being shipped from one country to another. For the destruction 

 of superficial vegetative portions of parasites or their productive spores, spraying 

 with fungicides is of value. This, however, should rather be used as a preventive. 

 The spread of much of the disease to be found in cacao estates might probably be 

 prevented if spraying with fungicides — such as Bordeaux mixture— were adopted 

 as an estate duty. 



(3) Rotation of crops is to be recommended for the purpose of checking 

 disease, especially when the disease is present in the form of mycelium or resting 

 spores in the soil. The fungus that causes the root disease may frequently be 

 successfully starved out by a rotation of crops- With permanent crops such as 

 cacao, rotation cannot be practised ; but in such cases root diseases may be pre- 

 vented from spreading if the infested area is isolated by digging trenches. The 

 disease is thereby confined in extent. Such areas should be cleared, the affected 

 trees dug up and destroyed, and the soil treated with quantities of lime in order 

 to kill out some, if not all, of the mycelium of the fungus. After the ground has 

 been allowed to rest for some time, and has been carefully cultivated, fresh supplies 

 may be planted with little fear of their being attacked. 



(4) The raising of the disease-resisting varieties of plants has recently 

 become recognized as a matter of considerable importance. Many of the seedling 

 sugar-canes that have been raised by this department are capable of withstanding 

 certain fungus diseases much better than the older varieties, and the wilt disease 

 of cotton and cowpea has been successfully overcome in the United States by 



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