Diseases 251 



wash and the solution of bluestone are slowly 

 poured together into a third tub holding about 

 50 gallons. When the mixture is complete, 

 stir and place therein a clean, bright knife- 

 blade for a minute. Remove the knife-blade, 

 and if it is still bright the Bordeaux mixture 

 is safe, but if it appears reddish, more lime- 

 wash must be added until the blade does not 

 become discoloured. The mixture must be 

 stirred before use. There are also, however, 

 some very effective proprietary insecticides 

 obtainable ready mixed for use. 



But prevention is always better than cure, 

 and it seems that with care leaf disease at least 

 can be kept at a distance. On an estate in the 

 West Indies where the disease appeared, trees 

 growing on light, dry soil seemed to have been 

 the ones attacked, and in such a case manuring 

 and tilth are absolutely necessary ; but Rorer 

 tells us that the leaf disease is only to be found 

 on trees in damp situations, and can doubtless 

 be easily controlled by the use of Bordeaux 

 mixture. With regard to the " little leaf" 

 disease, Rorer, on the other hand, says all 

 badly attacked trees should be destroyed. As 

 the name suo-aests, this trouble causes the 



oo ' 



crown to come out with small leaves, and they 

 continue to grow smaller and smaller, until 

 eventually the whole crown simply dwindles 

 away. Such cases are exceptional, but when 

 they do occur, the trees Rorer tells us 

 seldom outgrow the trouble. As a likely cure, 



