368 REPORT OF THE COMMISSIONER OF AGRICULTURE. 



ida, although it attacks them indiscriminately with others of the Citrus 

 family, when transplanted to open ground, and it may exist upon them 

 in small numbers in their native swamps. 



It is said that a few years ago rust was entirely unknowu, hut the 

 orange industry in this State is of such recent growth that attention has 

 not long been directed to this matter. When but little fruit was pro- 

 duced, occasional discolorations of the rind would naturally pass un- 

 noticed. 



Periods of Increase. — As is the case with most invasions of insects, the 

 pest, although increasing rapidly for a time, is likely to reach a maxi- 

 mum in a few years and afterward decline. This has been the expe- 

 rience in former years with scale-insect, and is attributable to compar- 

 ative immunity from enemies and parasites at the outset. As the num- 

 ber of their enemies increases, that of the destroyers diminishes, until in 

 time a state of equilibrium is reached, which is only disturbed tempo- 

 rarily by the changing conditions of climate, or other and obscure 

 causes. 



It seems probable that the Eust-mite has reached or is already past 

 the period of maximum destructiveness, and that succeeding \ears will 

 witness its subsidence. The mite has at present few enemies, and of 

 these the most important are unfortunately not abundant. They give 

 promise, however, of greater efficiency in future, as they belong to 

 families many of whose members are as prolific as the Rust-mite itself. 



Geographical Distribution. — Rust appears to be known upon the orange 

 only in Florida. Within the limits of the State, however, its presence 

 is universal. No section, whatever claims may be made to the contrary, 

 is exempt. 



REMEDIES. 



Influence of Soil and Methods of Cultivation. — The effect upon the 

 prevalence of rust of various systems of cultivation and of applications 

 to the soil, for the purpose of changing its nature or supplying assumed 

 deficiencies in its composition, has been the subject of endless discus- 

 sion, and of experiments affording negative or conflicting results, which 

 cannot profitably be reviewed here. 



Suffice it to say, no method of combating rust by special treatment of 

 the soil, or other indirect action through the plaut, has been proven 

 effective. By forcing with fertilizers or high cultivation, no improve- 

 ment is effected in the color of the fruit. This depends, not upon the 

 condition of the tree, but rather upon the number of the mites, which 

 is, in fact increased by an abundant supply of new growth and a con- 

 stant succession of fresh and vigorous leaves. 



It seems, however, to be an established fact that the fruit is less 

 liable to rust upon low than upon high lands. Groves planted upon 

 moist, rich hammock or clay soils produce, as a rule, brighter fruit 

 than those upon high, sandy pine lands. 



This result is commonly attributed to the abundance of moisture in 

 low ground j but it may be more directly due to the denser shade 

 afforded by a more vigorous foliage and reduced radiation from a darker 

 soil. In the native wild groves, which are always densely shaded by 

 forest, neither rust nor mites are found, and the same immunity is 

 enjoyed by cultivated trees planted in similar situations. 



Preventive Measures. — It is not at present possible to suggest any 

 preventive measures that can be universally adopted, nor are precau- 

 tions likely to avail much against an enemy which already exists, even 

 if it noes not always make its presence known, in almost every grove 

 and nursery in the State. 



