DISEASES OF COFFEE 229 



sufficient, where the soil is poor, or where cultivation and manur- 

 ing are neglected. It is by improvements in these directions 

 that the disease should be combated. The question of spraying 

 is one that does not seem likely to arise, at any rate in the West 

 Indies. The disease has been reported to be more severe in its 

 effects in Africa. 



Zonal Leaf Spot. 



A leaf spot disease described from Porto Rico takes the form 

 of large spots characterised by concentric rings, sometimes 

 incomplete and frequently coalescing. On the under side of 

 the mature spots a thin white mould appears, which in places 

 becomes more condensed. This bears Cephalosporium fructi- 

 fications, and by inoculations from pure culture the fungus has 

 been shown to be parasitic and to be the cause of the spots. 

 The affection is most frequently found on the best grown trees, 

 young and well-shaded leaves being most susceptible. It has 

 been seen on all the varieties in cultivation, but is nowhere 

 abundant. 



Bark Disease. 



A disease of stems occurs to some extent in Porto Rico in 

 which local bark-rot occurs in situations ranging from near the 

 crown to some feet up the stem, and is believed to commence 

 from wounds of mechanical or insect origin. The disease develops 

 its effects slowh', finally causing the bark to dry up and fall away, 

 leaving the wood exposed and revealing the callosed margins 

 of the healthy bark beyond. The presence of the affection ia 

 recognisable by the smaller diameter of the stem where the death 

 of the cambium has prevented the deposition of new wood. 

 Under the diseased bark the wood is blackened. G. L. Fawcett, 

 who describes the disease, reports that a fungus of the genus 

 Fusarium is always present in the affected tissues, but that 

 inoculations with pure cultures have failed to produce the 

 disease. It is communicated readily to healthy stems by means 

 of small pieces of diseased material and when thus transferred 

 has shown itself to be rapidly destructive to the living tissues for 

 several inches above and below the point of inoculation. 



Nematode Diseases. 



The fibrous roots and the base of the stem of the coffee tree 

 are liable to infestation with the eelworm Heterodera radicicola, 

 a general and cosmopolitan parasite described in another section. 

 On the small roots gall-like swellings are produced and on the 

 stem the infested bark takes on a very rough and somewhat 

 swollen appearance, which may extend for a foot or so above the 

 soil. 



