32 



penning' has been practised to a considerable extent, are fre- 

 quently affected with foot rot. This is so generally the case as 

 to admit of little doubt that this practice has considerable to do 

 in inducing the disease. The extensive application of organic 

 manures appears also to aggravate the malady to some extent, 

 and their use in infected groves should be discouraged. 



Insect Diseases. 



With regard to the effect of fertilisation upon insects which 

 infest the orange, it may be said that the question Is little 

 understood. A general impression exists among the growers 

 of the State, that groves fertilised with blood and bone or barn 

 manure are more liable to be badly infested with injurious insects 

 than those fertilised exclusively with chemical manures. This 

 appears to be especially true in the case of the six-spotted mite 

 (Teranychas 6-maculatus) and the purple scale (Mytilaspis 

 citricola) ; judging from observations on many groves which 

 have been fertilised with chemical manures only, it seems 

 that this belief is well founded. There is some evidence that 

 the muriate of potash aids to some extent in preventing the 

 ravages of the rust mite. Dr. Smith, of INTew Jersey Agri- 

 cultural Experiment Station, has found nitrate of soda and kainit 

 to be very active insecticidal fertilisers. These have not been 

 used to any extent in fertilising orange groves in Florida, and 

 no data have been obtained as to their effect on orange insects. 

 It is improbable that they would prove more effective than 

 sulphate of ammonia, or sulphate and muriate of potash, and 

 they should be thoroughly tested to determine their value as 

 fertilisers for the orange. 



Summary. 



Summarising it may be said : 



(1.) By a proper combination of the various elements used in 

 fertilisation, one can undoubtedly largely govern the quality 

 and flavour of the fruit. 



(2.) To obtain a fruit with thin rind, use nitrogen from in- 

 organic sources in moderate quantities, with considerable potash 

 and lime. 



(3.) To sweeten the fruit, use sulphate of ammonia in con- 

 siderable abundance, decreasing the amount of potash. 



(4.) To render the fruit more acid, increase the amount of 

 potash and use nitrogen from organic sources. 



(5.) If it be desired to increase the size of the fruit, as is 

 sometimes the case, apply a comparatively heavy dressing of 

 nitrogen in some organic form and slightly decrease the other 



