PORTO RICO EXPERIMENT STATION. 445 



INSKCr ENEMIES OF CITRUS STOCK. 



The red scale {Lecanimn Item Isphseri cum) is pr()l)ably the most eom- 

 nioii scale on the orange here; since it infests many other plants it is 

 liable to a{)pear in any orchard at any time. Two to four applications 

 of kerosene emulsion are usually necessary to rid a badly infested tree 

 of this pest. This scale is sometimes parasitized by a hymenopter, as 

 well as by the connnon whitish fungus, which is proving to 1)0 of great 

 importance. 



The purple scale {Mytllaspis citricola) is very common in all parts 

 of the island; it is parasitized by a '' red-fruited" fungus {Sphserontllhe 

 coccophiUt) and a black slow-growing fungus {^Myrlanghun, durisei)^ 

 which was tirst observed at Naguabo and which is fairly common at 

 ^lavaguez. 



The chart' scale ( Chionatipix citri) is common eveiy where on orange 

 and lime. 



Ax2>i(11<)tut< atirantil is rare but apparently spreading. 



Cer<>phv<te>i jlorideiuiH was noted only in an orchard near Naguabo. 



Chj^ysomphalm aonidum. is rarely met with as yet. 



DtictylopiuM Citri is not common. 



AapidioUix articulatu^'< occurs commonly in the eastern and northern 

 districts. 



(tenerally speaking the orange growers in Porto Rico are not giving 

 suthcient attention to the scale pests in their groves; the spraying is 

 entrusted to native laborers, who are certain to leave more or less 

 uns])rayed surface on each tree. One of the most promising groves 

 has been veiy seriously injured by allowing the pests to become 

 thoroughly established. Moreover, the insecticides are not always care- 

 fully made, and worse still, perhaps, old and badly infested native 

 seedling trees are f requentl}' left standing in or near the new orchards 

 to breed and distribute endless generations of scales to the nurseries 

 and young trees. Thousands of acres in the north part of the island 

 have been planted with oranges in the past two or three j^ears, and 

 though it is natural that in this hurry and optimistic excitement such 

 dangers are overlooked by the average planter, the prospective injury 

 from scale insects in these new orchai'ds might be very greatly les- 

 sened by a more careful attention to their present requirements. 



In some groves considerable damage is being caused b}' a small brown 

 ant which bites the bark and feeds upon the gum which exudes from the 

 wound. Small bi-anches are frequently girdled, and the loss of sap 

 and gum through the munei'ous op(>n wounds in time weakens the 

 young tree. When not too close to the trunk of the tree a nest may 

 be destroyed by ])()uring into it a few spoonfuls of carbon bisulphid 

 and then covering with a wet gunny sack, but young trees are some- 

 times killed by the use of too nnich of the licjuid near the roots. 



