DISEASES AND PESTS 47 



be estimated in terms of the survivors, instead of being com- 

 pared with the actual value of the trees destroyed. 



Close planting favours the spread of the disease, by 

 preventing the evaporation of moisture from the young 

 shoots. 



The bud rot in East Africa is known from a letter 

 cited by Petch, who quotes from it : "If the dead 

 tree is not immediately destroyed by fire, the disease 

 rapidly spreads to the neighbouring trees, and finally 

 throughout the whole plantation." 



Luzon. — The history of epidemic bud rot in the 

 province of La Laguna, in the Philippines, is here given 

 at some length because the measures employed against 

 it have in this case proved their thorough efficiency. 

 The disease was first reported in 1907, but had existed 

 in the region for many years. The description of it is 

 taken from a report made by myself in 1908. 



In the badly infested districts there are patches where 

 almost every tree is smitten, and larger ones where fully half 

 of the trees are dead or dying. Under conditions favourable 

 to it the' disease will kill half of the trees in a single year. 

 Under less favourable conditions it is less violently epidemic ; 

 and in its present form it will never prove violently destructive 

 in most parts of the Philippines. The fact that a given tree 

 escapes one year is no guarantee that it will not be killed the 

 next. Under conditions favourable to the disease it is only a 

 question of time, unless vigorous restrictive measures are carried 

 out, when practically every tree will succumb. 



The climatic condition permitting the disease to be exceed- 

 ingly destructive is a very moist atmosphere. Bud rot is 

 epidemic only in the upper belt of coco-nut country about Mt. 

 Banahao, which is one of the most humid districts in the Islands. 

 The coco-nuts at the foot of San Cristobal, which are compara- 

 tively unreached by the wet ocean winds, are free from bud rot. 

 Below the zone where the bud rot is most at home, there is of 

 course a region in which infection can occur under conditions 

 temporarily favourable, or affecting single trees or small 

 localities. As every tree for miles around is likely to receive 

 the germs, it is inevitable that in this lower zone some will be 

 infected each year. As these die the damage is cumulative, 

 and the gaps caused in lower groves increase in number or size. 



