REPORT OF THE ENTOMOLOGIST. 



369 



Those who advocate forest culture for the orange may justly claim 

 for it the advantage of affording comparative immunity from rust; 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 towards the exclusion of such pests 

 as the Rust-mite and the scale-insect by properly arranged natural 

 screens. Narrow belts of original forest, with its undergrowth, may 

 be left, at least on the southeast side of the grove, or, on high land, the 

 tall pines may be supplemented by hedge-rows of the native holly, the 

 jujube, or other evergreen shrubs, which thrive upon 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 tlieir direct 

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

 disseminated. 



Application of Insecticides. — As the Rust-mite lives exposed upon the 

 surface of the plant, neither inhabiting a gall, nor making any protec- 

 tive covering for itself or young, it is not a difficult matter to reach it 

 with insecticides thoroughly applied. The adult mites are very deli- 

 cate, and readily succumb to applications of moderate strength, but the 

 eggs possess much greater vitality, aud require for their destruction, 

 solutions of great penetrating power. The immature mites, while un- 

 dergoing their transformations, are also difficult to kill, and appear to be 

 specially protected by t he old skin, within which their changes take place. 



These three stages, the adult, the molting young, and the egg, exist 

 simultaneously at all seasons of the year. The development of the mite 

 has been shown to be very rapid. The eggs hatch in four or five days, 

 the time extending rarely, in winter, to two weeks. Molting takes 

 place in seven to ten days, and lasts two days. Eggs are probably laid 

 in a few days after the molt. 



In applying remedies, it follows from these data that if the mites 

 alone are killed, and their eggs left alive, \ oung mites reappear imme- 

 diately", adults are found in ten or twelve days, and fresh eggs are de- 

 posited within two weeks. If the molting mites are also left alive, 

 very little good can be accomplished, as afresh crop of adult mites and 

 eggs will be produced in two or three days. 



In combating Rust-mite the difficulty in killing the eggs compels us 

 to adopt one of two alternatives. We must either use powerful insecti- 

 cides, in solutions even stronger than are required for scale-insects, or 

 else make several applications, at short intervals, of washes competent 

 to kill the mites only. In this way the trees may be freed of mites, by 

 killing the young as they hatch, and not allowing any to reach the 

 adult stage and produce a fresh crop of eggs. 



The following substances have been tried and their effects noted upon 

 the mites and their eggs : 



Whale-oil Soap. — The action of this substance upon the mites is pecul- 

 iar. A trace of it in solution causes them to relinquish at once their 

 hold upon the leaf. All other liquids that have been tried, even if they 

 kill the mites, increase the tenacity with which they cling to its sur- 

 face. All the free* mites are at once reuwed from leaves dipped in a 

 solution of 1 pound to 100 gallons of water. Stronger solutions are, 

 however, required to kill them or their eggs and the dormant (molting) 

 young. 



*This term includes adults and young not dormant, or undergoing transformation. 

 24= A— '84 



