DISEASES OF MINOR FRUIT TREES 239 



Nutmegs. 



The cultivation of nutmegs on a commercial scale in these 

 islands is almost confined to Grenada, where it exists as a sub- 

 sidiary industry on cacao plantations suitably situated in the 

 wetter upland districts. The trees often attain to a height of 

 40 or 50 feet, and sometimes more, so that the conditions pre- 

 vailing closely resemble those of forest. The diseases which have 

 appeared are well marked, but have been the subject of no 

 close study. 



Canker, 



A somewhat serious disease has been met with from time to 

 time, the symptoms of which, according to the agricultural 

 officers reporting it, are identical with those of cacao canker. 

 R. D. Anstead described it as causing the trees to die back from 

 the head, or, in the case of individual branches affected, from the 

 tips of the twigs. In such cases the bark below is unhealthy 

 and in places bleeding occurs corresponding to that of cacao 

 canker. The sap in these places is of a rich dark red colour 

 and has a foul odour. In the late stages gum may be exuded 

 from the trunk near the base. The disease has been known 

 to cause the death of numbers of large trees. 



Nothing definite can be said as to the causation of the disease, 

 but it has been found to be amenable to the same treatment 

 as cacao canker, to which reference should be made. 



Perforated Leaves. 



A common affection in Grenada is a leaf-spot, the final stage 

 of which is represented by clean-cut approximately circular 

 holes of 1.5 to 10 mm. diameter. The brown spot which pre- 

 cedes this condition contains the fructifications of an undeter- 

 mined species of Phyllosticta, which appears to be the cause of 

 the affection. Hundreds of species of this genus of fungi have 

 been described, from the leaves of almost as many species of 

 plants, often giving rise to affections of this class. How far 

 they are interchangeable has seldom been determined, but they 

 are generally regarded as specific within a narrow range. 



In the absence of knowledge concerning the conditions 

 governing the disease on nutmegs no remedial measure can be 

 suggested. Spraying would be impracticable on trees of large 

 size on account of the low value of the product. 



Red Rust. 



The alga Cephaleuros mycoidea is very common on nutmeg 

 leaves. It has not been reported as affecting the twigs, in 

 which position it produces its principal ill-effects. (See Chapter 

 XVI.) 



