FRUITS 257 



great disadvantage of destroying our friends the scale 

 parasites along with the scales. Except in cases of 

 extreme necessity it is probably unwise to attempt 

 the treatment of entire orchards for scale. Great 

 care should be taken in making new plantings to 

 avoid trees from infested nurseries, since this is the 

 way in which this trouble is usually introduced. 

 Close watch should be kept, and individual trees 

 should be promptly treated as soon as scales threaten 

 injury. In this way and by giving good cultivation 

 and general care, expensive general spraying or 

 fumigation, with its wholesale destruction of the 

 useful scale parasites, may usually be avoided. Scale 

 insects seem to multiply faster and do much more 

 damage on feeble, slow-growing trees than on vigorous 

 ones. The greater vigor of growth of young trees 

 on rough lemon roots is thought by some to make 

 them less susceptible to scale than when budded on 

 the sour orange. 



The white fly (Aleurodes) is an insect closely re- 

 lated to the scales. At the present time in Florida 

 it is more feared than all the other orange pests com- 

 bined, since its natural enemies have failed to hold it 

 in check and none of the usual remedies seem capable 

 of satisfactorily combating it. It is always accom- 

 panied by the sooty mold, which adds greatly to 

 the injury it occasions. It also occurs in Cuba, as 

 specimens of it have been collected there, but so far 

 it is not in sufficient numbers to prove injurious or 

 to attract attention. Whether this practical im- 

 munity is due to the presence of more active natural 

 enemies has not been determined. The closely re- 



