EXCISING CANKERED TISSUES 97 



Dense shade and excessive moisture encourage both 

 the development of the disease in infected trees and also 

 the propagation of the disease. 



The excision of diseased areas and reduction of shade 

 were attended with satisfactory results. 



The dry season, when the trees carry a minimum 

 quantity of flowers and fruits, is considered the best 

 time to carry out the work of excising cankered tissues. 

 At least a | in. of the healthy bark surrounding the dis- 

 eased portion should be cut away, in addition to the latter. 

 A sharp pruning-knife should be employed for this 

 operation. Where the cankered tissues extend more 

 or less round the stem it would be advisable to remove 

 them gradually, so as to avoid "ring-barking" and 

 thus killing the tree. 



Trees which have been excised should be examined 

 periodically with a view to discovering whether the 

 previous operation was effective and if new areas of 

 infection have developed. 



All excised tissues should be carefully collected and 

 burned, as any left lying about the plantation may be the 

 means of infecting healthy trees. It is advisable to anti- 

 septicise all wounds made in cutting out the diseased 

 tissues by painting them with tar and resin oil. All 

 wounds found on the trees should be similarly treated, 

 as these afford convenient infection areas for the spores of 

 the canker fungus. Badly infected trees which are 

 producing healthy suckers from the base of the stem 

 should be cut down just above them, as this will en- 

 courage the suckers to grow rapidly and to take the 

 place of the parent tree. Branches or trees killed by 

 canker should be pruned down and burned. 



The advisability of reducing the shade to let in more 

 sunlight to the cocoa trees should also receive due con- 

 sideration. Where trees are densely shaded the excision 

 of cankered tissues will not be attended with satisfactory 

 results. Wright (loc. cit.) states : " On one area where 

 the excising, collecting, and burning of cankered tissue was 

 subsequent to the thinning out of the shade, the yield of 

 the cocoa has been increased from 1 cwt. to approxi- 

 mately 5 cwt. per year. On an adjacent area where the 

 shade was allowed to remain dense, but the other curative 

 methods adopted, the yield remained almost stationary, 



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