158 TRINIDAD AND TOBAGO BULLETIN. \XVIIL ■{. 



to it occurring soiuetimes in one month and sometimes in anotlier its 

 effect is almost eliminated in the process of averaging. It will be seen 

 raore distinctly in the graphs M'hich follow, particularly in Figs. 7, 9, 

 -and 11. 



The cane in Trinidad is usually planted from August to November 

 <" wet season plants ") or during the drj' season (" crop plants'") and is 

 •cut during the dry season of the following year. " Plant canes " (first 

 cutting) have about eighteen months growth and " ratoon canes " (second 

 and third crops) have twelve months growth. 



The crop is therefore liable to be affected by the rainfall during the 

 <?ighteen months previous to its cutting, which operation is carried out 

 from February to Mav in normal seasons. 



MONTHLY RAINFALL AND 15LIGHT. 



An attempt has been made to find the rainfall conditions associated 

 with "blight" by plotting, in Figs. 6 and 7 the rainfall on one estate 

 in five good years, in which few froghoppers were seen and little 

 ■ilamage reported, and, on the other hand, in six years in which 

 froghoppers were abundant and damage wide-spread. 



An inspection brings out the following points of interest: — 



(iooD Years.— (1909-10. 1910-11. 1P14-15. ]915-](), 1916-17). 



(1.) Dry season usually shorter and less severe, .fanuary olt<'ii 

 wet (1910 exceptionally wet). 



(2.1 -July rainfall b; low 9-7 in all cases except one (1915). 



(o. Indian Sunnner less marked. Hainfall only once below five 

 inches in either September or October. 



Bad Years.— (190G-7, 1907-8, 19il-l-2. 191'2-13, 1917-18, 19l8-19>. 



(I.) Dry season usually longer and more severe (191G exception- 

 ally long and dry). January usually dr^-. 



(•2.) -luly rainfall above 9'7 inches in all cases except o e(nni, 

 which had a wet June). 



Cd.) Indian Summer distinct. Rainfall five inches or below in 

 four years in September, and in five years in October. 

 Never above five inches in both of these two months. 

 Particularly low in October. 



0.1 the whole the years of wide spread blight are years of extreme 

 •contrast in rainfall characterised by alternations of excessively wet and 

 dry weather. 



In order to confirm the above results a comparison has next bean 

 made between tlie rainf ill o.i four estates during 1916-17 when the 

 ■damage due to blight w.is ahnoit negligible (Fig. 8) and the rainfall 



