114 INSECTS AFFECTINO THE ORANGE. 



Suflice it to say, uo method of (loinbating rust by the iudirect action 

 tbiougli the plant of chemical substances applied to the so'.l has been 

 l)roven efiective. By forcing with fertilizers or high cultivation, uo im- 

 provement 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 ; but it may be more directly due to the denser shade af- 

 forded 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 en 

 joyed by cultivated trees planted in similar situations. 



Preventive Measures. — Any means which will enable us to produce on 

 the light, sandy soil of the uplands those conditions of shade which 

 appear natural and grateful to the Orange, and which we have seen are 

 unfavorable to the increase of the Eust-mite, should, if the foregoing- 

 account is correct, give immunity from Eust. In point of fact, there is 

 strong evidence to warrant the belief that with intelligent management 

 almost any grove may in a few years be made to produce bright fruit, 

 by reducing the radiation and darkening the soil, (1) with mulch, or, 

 still better, with a liberal coating of muck, (2) by encouraging the 

 branches to grow low and spreading, and especially avoiding the vicious 

 ])ractice of trimming young trees too high. 



Other ways of shading the ground and ]>roinoting vigorous leafy 

 growth will occur to every orange-grower. 



Those who advocate forest culture for the Orange may justly claim for 

 it the advantage of affording comparative immunity from rust j but a 

 discussion of the merits and demerits of this and other systems of cul- 

 tivation must be left to the horticulturist. 



It may, however, be proper to suggest that where isolation is prac- 

 ticable much can be accomplished toward the exclusion of such pests as 

 the Eust-mite and the Scale-insect by properly arranged natural screens. 

 Narrow belts of original forest, with i*:s undergrowth, may be left, at 

 least on the southeast side of the grove or on high land ; tiie tall pines 

 may be supplemented by hedge-rows of the native Holly, the Jujube, or 

 other evergreen shrubs, which thrive ujiou uplands in the South. 



Such wind breaks not only protect the bearing trees and fruit from 

 the whipping action of southeasterly gales, but afford the best and only 

 hindrance to the spread of Mites and Bark-lice, prohibiting their direct 

 importation upon spiders and other insects, through whose aid they are 

 disseminated. 



