34 COCONUT PLANTER'S MANUAL. 



The discovery that a species of Ph/tophthora was usually present 

 on fallen nuts led to the suggestion that the disease might be preven- 

 ted by the application of a fungicide such as Bordeaux Mixture" 

 Experiments in 1923 to determine the value of this spray as a preven- 

 tive of nut-fall gave negative results. The number of fallen, but 

 immature, nuts in the sprayed plot was approximately equal to that 

 in the unsprayed plot. The climatic conditions of that year were 

 unfavourable to the growth of the fungus and the pathogenic organ- 

 ism was not found on any of the fallen nuts examined from either plot. 

 In view of the absence of a pathogenic organism it became evident 

 that causes other than fungus attack might lead to a similar diseased 

 condition. 



A serious case of fruit fall of coconuts before maturity is reported 

 from Indo-China, in December, 1 920. The appearance of the fruit 

 suggested a parasitic disease, but comparative analyses of the soils of 

 various plots led to the conclusion that the fundamental cause was 

 the insufficient nourishment of the roots, which was remedied by the 

 application of nitrogenous manures. The description of the disease 

 and the presence of certain organisms on the fallen fruits suggests the 

 the condition known in Ceylon as "Nut fall." Observations in Ceylon, 

 however, do not lead to the same conclusion, viz., that its cause is an 

 insufficiency of nitrogenous manures. Nut-fall in Ceylon is known to 

 occur in plots which are regularly and liberally manured, whereas it is 

 absent from other plots which rarely receive any manurial treatment. 



The discovery that the abscission of fruits of Juglcms calif ornica 

 quercina is due to water deficit beyond a certain limit, and that a 

 similar cause also leads to the fall of Citrus fruits, may throw some 

 light on the problem of nut-fall of coconuts in Ceylon. 



A water deficit has already been shown to affect the setting of 

 young coconut fruits in Ceylon. Following a prolonged period of 

 drought, there is an increased fall of the female flowers, or button 

 nuts,'* as they are frequently termed. The fall of such "buttons" had 

 previously been attributed mainly to the lack of fertilization, but, 

 undoubtedly, other factors besides fertilization play an important part 

 in bringing this about. The June drop of peaches in Delaware was 

 generally attributed to incomplete fertilization, but an examination of 

 a large amount of cytological material gave conclusive evidence that 

 June drop was not the result of improper fertilization but of other 

 physiological factors. It has also been ascertained that moisture is 



