1919.\ 153 



RAINFALL, SUGAR PRODUCTION AND PROGHOPPBR 

 BLIGHT IN TRINIDAD. 



By C. B. Williams, M. A., F.E.S., 

 Entomologist in Charge of Frogbopper Investigations. 



INTRODUCTION. 



The disease known as " Blight " or " Froghopper-blight " of Sugar 

 Cane has been known in Trinidad for many years. The Froghopper 

 {Tomasjois saccharina) was first mentioned in 1889 but, even before the 

 ■connection between the disease and this insect was recognised, old 

 descriptions of injury leave little doubt that similar conditions were 

 present many years before. 



From the very earliest reports there has been a tendency to consider 

 adverse weather conditions as one of the most important causes of 

 blight ; both want of rain, and excessive rainfall being suggested by 

 various writers. 



H. Cruger, in the first account of blight (written in 1863, published 

 in 1892) considers one of the most important causes as " a want of rain 

 at a certain period." 



.T. H. Hart in his " Report on Sugar Cane Bhght " 1890, says that 

 the canes recovered on the advent of suitable weather. 



A.E. Collens in 1906, reporting on an outbreak at Harmony Hail, notes 

 that " the dry season had been followed by heavy rains with rather long 

 intervals of strong sun." 



G.T. Fenwick {Proc. Agr. Soc. Tdad d- Thgo. IX. 1909, p. 558) writes 

 ^' the attacks, whether from insect or fungus pests, were usually noticed 

 to follow periods of abnormality in the seasons and generally disappeared 

 when weather conditions were again normal." 



P. L. Guppy in 1911 (BiiU. DepL Agr. X. 1911. p. 82) says "the 

 extremely dry weather of this wet season has been particularly 

 unfavourable to the growth of the cane and at the same time favourable 

 to the rapid increase of the froghopper." 



F. W. Urich in 1913 [Circular No. 9, Board of Agr. p. 30) says that 

 " a long and severe dry season generally tends to cause a severe out- 

 break of froghoppers, whereas a m'ld one does not app'^av to produeo 

 such large numbers." He gives figures of the rainfall at Woodford 

 Lodge Estate showing that in 1908 and 1912, both years of severe blight, 

 the dry season was long and severe. 



J. C. Kershaw, on the contrary, in 1914 (Bull. Dept. Agr. XIII. 1914. 



p. 48) says that " there is a common belief that in wet seasons the cane 

 suffers less from froghoppers than in dry " but that " there is no real 

 evidence that climatic conditions affected the incidence of froghoppers 

 at all." 



