SECTION VII.— FACTORS INFLUENCING BLIGHT PREVALENCE. 97 



Fig. 20. 



Fig. 20- Annual Rainfall on six Trinidad sugar estates 1907 to 1918 with the total 

 crop for the corresponding period. Note the absence of relation between the two. 



The conclusions reached were summarised as follows, (Williams 1919 

 E. p. 167) : 



" (1) Alternation of wet and dry periods during the growth of the caue 

 is an important factor in determining the prevalence of blight. 



" (2) A. long dry season followed by unusually heavy rains in June or 

 July is frequently connected with wide-spread blight. 



" (3) The most important climatic condition however appears to be 

 the severity of the ' Indian Summer', a dry period in September or 

 October. A. severe Indian Summer is a general condition both of 

 localities damaged by blight in one year and of years of wide-spread 

 blight in one locality." 



The evidence of these conclusions is given in full in the above report, 

 but for convenience four of the diagrams are reproduced here. 



