I5-P DISEASES OF VARIOUS CROPS 



after the rains lireak out and completely disappears after the close of the mon- 

 soon with the return of the dry and sunny weather. 



The damage caused by " Black thread " is very serious; in 1915 in a 

 plantation of 77 000 trees in Burma, tapping was prevented in 12 000, the 

 loss of rubber being estimated at two to three thousand pounds. 



Treatment ; i) the fungus fructifies very poorly on the stem but very' 

 profusely on the fruits which should be considered as the principal source 

 of infection ; infected fruits should therefore be collected and destroyed when 

 they first appear ; 2) pruning should be freeh^ indulged in, so that penetra- 

 tion of sunhght and free circulation of air are ensured ; 3) tapping should 

 be stopped and the tapping cuts treated with a 20 per cent solution of car- 

 bolineum every five days. 



11^2 - Corti'cium salmonicolor ("pink disease") of Cacao, in the Island of 



Trinidad, Antilles (i;. — • Rorer, J . B., in Bulletin of the DepoMment of A'^riculturc, Trini- 

 dad and Toba'^o, Vol, XV, Part. 3, pp. 86-8cj, I pi., Port-d'Espagne, 1916. 



At rare intervals dxiring the past seven years the cacao disease known 

 as "pink disease" has been recorded on several plantations in the nor- 

 thern and eastern parts of Trinidad. The disease receives its name from 

 the fact that the attacked branches, especially on the lower or shaded side, 

 are covered with a pink incrustation which is the fruiting stage of the fun- 

 gus that causes the disease, Corticium salmonicolor Berk, and Br. (and not 

 C. lilacino-luscum Berk, and Curt, as was formerly believed). 



Up to the present time the fungus is not a really serious menace to ca- 

 cao cultivation in the West Indies. 



It can live at the expense of great many plant hosts and so has caused 

 considerable damage elsewhere : for example, to Hevea in the United vStates, 

 to coffee in Java, etc. 



In the case of cacao the small branches are most often attacked and are 

 rapidly killed ; if the fungus in the course of its rapid development reaches 

 the larger branches the whole crown of the tree ma}^ become infected. The 

 leaves on the diseased branches wither, tvirn brown and fall to the ground. 



Where the disease occurs sporadically the infected branches should be cut 

 out and burnt immediately. If the diseased parts have to be carried out 

 of the plantations they should be put in bags to prevent the dispersal of the 

 spores of the parasite. If the disease should assume serious proportions 

 Bordeaux mixture or other fungicides could be usefulh^ employed. This is 

 a simple matter in cacao plantations or in rubber plantations where the 

 plants are two or three 3^ears old. 



In cases of serious attack in old rubber plantations spraying is not re- 

 commended on account of the almost insurmountable diflftculties met with 

 in treating large trees. The disease is more effectively dealt with by cutt- 

 ing out and burning the affected parts, where this is possible, or where onlj'' 

 a limited number of trees are attacked. If the infection is wide spread good 

 results have been obtained by treating the diseased parts with tar as soon as 



(i) See also Bulletin Sept. i'ii3, Xo. no.", and Bulletin I'eb. 1915, No 135. (Ed.). 



