27 



In fortilizinc;, most of the ^jrowors apply a small amount three to 

 four times a year, which of course is good practice, but the amount is 

 generally too small. This is an offhand statement, as no experiments 

 have so far been made in fertilizing the orange trees in Porto Rico, but 

 the groves which have received a large amount of fertilizer are cer- 

 tainly far ahead of those which have received less. As to the amount 

 and kind of fertilizers, the question seems to be limited to how much 

 the tree will take up. Large applications of nitrogen in organic forms 

 have not so far been followed by die-back; in fact, die-back has not yet 

 been observed on the island and there seems to be no danger on that 

 point. 



INSECT PESTS. 



Numerous experiments for combating the chief diseases and insects 

 have been conducted by the horticulturist as well as by individual 

 orange growers throughout the last year. In order to fidly describe 

 these it would require more space than would be desirable in this 

 report; furthermore, it is questionable whether it would be necessary. 

 It is firmly believed by the horticulturist and by many of the growers 

 that the present impediments to orange growing in Porto Rico are 

 merely trifling troubles which can largely be overcome by intelligent 

 planting and cultivation. 



The purple scale {Lepidosaphes heckii Newm.). — In studying the 

 problem of combating this pest it was found that on a few trees in the 

 station orchard which were well protected from wind and sun the scale 

 was kept in check by three species of fungi. An attempt was made to 

 disseminate these through the grove, but it was not successful; evi- 

 dently the conditions were unfavorable. Trees in natural groves, 

 which are protected from wind and sun and where the air is uniformly 

 moist, are always free from scale, and several attempts to distribute 

 scale through such trees have always resulted in failures. Practically 

 the same results have been obtained in other groves, although after a 

 tree has become literally covered with scale the fimgi can not be relied 

 upon even when conditions are made favorable to their growth. It 

 should therefore be the aim to plant the shade first, and to set no tree 

 which is not perfectly free from scale. 



The orange snow scale {Chionaspis citri Comst.) nearly always fol- 

 lows a severe attack of the purple scale. It is difficult to overcome, 

 because the trees are at that stage not generally in condition to with- 

 stand concentrated sprays. It is improbable that this scale will cause 

 much damage if the purple scale is kept in check. 



The red scale (CJirysompTialus Jicus Ashm.) has gained a foothold in 

 some of the groves, but it has been causing but little damage so far. 



The orange leaf-weevil {ExopJitalmus spengleri) and allied species is 

 causing considerable damage in groves which are not given clean cul- 

 tivation. Experiments made to destroy these pests with poisons have 



