56 



MAL-DI-GOMMA. 



The much-dreaded disease of foot rot, or mal-di-gomma, is probably 

 not produced primarily by improper methods of fertilisation, but seeme 

 to be considerably affected by the use of fertilisers and methods of cul- 

 tivation. Groves in which cow-j enning* has been practiced to a consi- 

 derable extent are frequently affected with foot rot. This is so gene- 

 rally the case as to admit 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 imects which infests 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-spot- 

 ted mite (Tetranychus 6-macalatus) and the purple scale (Mytitaspis 

 titricola) ; jndgingfrom observations on many groves which have been 

 fertilised with chemical manures only, it certainly 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 the New Jersey Agricultural 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 

 probable that they would prove more effective than sulphate of ammo- 

 nia or sulphate and muriate of potash, and they should be thoroughly 

 tested to determine their value as fertilise! s for the orange. 



SUMMARY. 



Summarising, it may be said : 



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

 tion one can undoubtedly largely govern the quality and flavour of the 

 fruit. 



(2) To obtain a fruit with thin ricd, use nitrogen from inorganic 

 sources in moderate quantities, with considerable potash and lime. 



(3) To sweeten the fruit, use sulphate of ammonia in considerable 

 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 is 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 elements. In the case of the tan- 

 gerine and mandarin, where a larger size is usually desired, a heavy 

 dressing of nitrogen fertilisers would favour this end, and is not objec- 

 tionable unless carried to excess. 



(6) Fertilisation has an important bearing on diseases. 



(7) Die-back, a serious malady, is in all probability the result of over- 

 feeding with nitrogenous manures from organic sources. These manures 

 if used at all should be applied with great caution. 



* A term used to designate the practice of penning cattle in orange groves over 

 night, using a movable pen, the position of which is changed every few days. 



