

A FORTNIGHTLY REVIEW 



OF THE 



IMPERIAL DEPARTMENT OF AGRICULTURE FOR THE WEST INDIES. 



Vol. XVI. No. 392. 



BARBADOS, MAY 



19i; 



Price \i. 



CONTENTS. 



137 



131 



Page. 

 Agriculture in Queensland 135 

 Barbados, Production of 



Provision Crojjs in 

 Caledonia New, Plants 



and Animals of ... . 

 Cattle in Different Coun- 

 tries, Age Determina- 

 tion of 

 Cotton Notes: — 

 Britisli Cotton Growing 



Associaton 

 Sea Island Cotton Mar- 

 ket 



Sea Island Cotton Pros- 

 pects 



Departmental Reports ... 



Gleanings 



Insect Notes: — 



Insect Pest." in tlie West 

 Indies in 1910 



... 133 



... 134 



134 



l;34 

 141 



140 



138 



Page. 



Items of Local Interest ... 132 

 Lateritu Formatif'U in 



Soils 143 



Market Reports 144 



Notes and Connnents ... 136 



Pig-keeping, Open-air ... 13(i 

 Plant Diseases: — 



Citrus Diseases in Culia 142 



Potash fruiii Felsi)ars ... l.">7 

 Queensland, the Divining 



Rod in 135 



Resistance to Disease ... 12!t 



Scientific Exphjration in 

 Central America and 

 the West Indies ... 130 



Soil Eviilution in Volcanic 

 Districts 135 



West Indian Products on 

 the London Market ... 143 



Resistance to Disease. 



T is becoming more and more evident as 

 .tropical agriculture develops in extent and 

 (comple.xity that we must take wider views 

 than in the past regarding the maintenance of health 

 in plants and animals. It is becoming necessary 

 to investigate more deepl}' the relationships that exist 

 between parasites and their hosts, and to study more 

 closely the intiuence of conditions of environment. 



The avenues of enquiry followed in the past have 

 not led very far towards great discoveries. When it has 

 become necessary to investigate a new plant disease or 

 infestation, the first line of attack has generally been to 

 find a causative parasite, then to study its life-history,and 

 ultimately to name it. After that it has been custom- 

 ary to suggest various expedients — legislation, various 

 forms of mechanical treatment like spraying, and 



sometimes modification in cultivation practices. Gener- 

 ally speaking the tendency has been to concentrate on 

 the parasite rather than on the host, and to neglect the 

 factors governing the relationship between the two. lb 

 is owing to this that economic entomology and to a less 

 extent mycology have failed, in many instances, to 

 appeal to the practical planter. The planter naturally 

 thinks first of the host, and it very often happens that 

 this instinct has a great deal to justify it scientifically. 



To get below the surface we must ask ourselves 

 why an individual is diseased or infested. Observations, 

 however minute regarding the fact that it is, are not 

 sufficient to aftbrd fundamental assistance in prevention. 

 Something more is required than diagnosis and the 

 application of expedients. 



The prevalence of disease is intimately associated 

 with what we term resistance'. A plant may be 

 resistant to a disease constitutionally, or on account 

 of external conditions increasing the plant's vigour. 

 Conversel}" it may be susceptible constitutionally or 

 because external conditions are inimical. Similarly the 

 intensity of parasitism by an organism attacking it 

 may be chiefly constitutional or largely the efifect of 

 external conditions upon the organism. Thus disease 

 will be most prevalent amongst constitutionally 

 susceptible individuals growing under conditions 

 unfavourable to the.se individuals but favourable to a 

 particular parasite. This implies, of course, the presence 

 of infection in the first place. 



These considerations lead us to group plant diseases 

 in the West Indies under two great classes: diseases 

 which are due to the existence of conditions unfavour- 

 able to the host; and diseases w hich are due to conditions 

 favouring the fungus. An example of the first group 

 is the root disease of the sugar-cane. Constitutionally 



