498 



JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 8 



before they enter the stalk, or the midrib of the leaf. It is quite 

 probable that this is one of the most crucial periods in its life history 

 and that many newly hatched larvae fail to enter the cane before they 

 are washed off by the rain. It was observed in Cuba that considerable 

 numbers of borer larvae were killed in young cane by the more rapid 

 growth of the central shoot of a cane plant than of the outer leaves. 

 Also, larvae were found which had been drowned in a mixture of water 

 and decaying cane juices which had collected in their tunnels after 

 rains. To avoid danger from these causes, many larvae were found 

 living outside the shoot, where they were exposed to the attacks of 

 predators or parasites. 



Summary 



The abundance of the smaller moth borer, Diatrcea saccharalis, the 

 most important pest of sugar cane in the New World, depends upon 

 two factors, rainfall and the burning of trash. Rainfall cannot be 

 controlled, but in many cases in Porto Rico and elsewhere trash is 

 needlessly burned. Burning trash increases the abundance of the 

 borer 100 per cent. It is desirable that the burning of trash be 

 avoided. 



Total Annual Rainfall and Average Infestation of Sugar-Cane by Diatr^ea saccharalis at Various Local- 

 ities IN Porto Rico, also Infestation in Fields were the Trash Was Burned and "R'here the Trash Was 

 Not Burned. 





Inches of 





Percentage of Infestation, 1914-15 



Locality 



Rainfall, 

















1914 



Average of 



Fields where Trash 



Fields where Trash 







all Fields 



Was Burned 



Was not Burned 





101 



6 



(8) 







6 



(8) 





95 



5 



(6) 







5 



(6) 





761 



11 



(15) 



13 



(6) 



9 



(9) 





72 



6 



(9) 



10 



(2) 



4 



(7) 





70 



11 



(4) 







11 



(4) 



Tea Baja 



70 



15 



(8) 



19 



(4) 



10 



(4) . 





66 



17 



(7) 







17 



(7) 



Vega Baja 



66 



39 



(9) 



44 



(5) 



26 



(4) 



Caguas 



58 



6 



(5) 







6 



(5) 



Yabucoa 



58 



37 



(5) 



60 



(2) 



22 



(3) 





55 



26 



(16) 



69 



(1) 



23 



(15) 



Juana Dias 



60 



32 



(9) 



34 



(8) 



18 



(1) 



Guayama-Josepha 



45 



47 



(4) 



47 



(4) 









24 



45 



(7) 



50 



(5) 



31 



(2) 



Potala 



27 



37 



(9) 



44 



(6) 



24 



(3) 



Ponce 



25 



48 



(8) 



48 



(8) 









23 



64 



(5) 



77 



(3) 



44 



(2) 





24 



76 



(S) 



76 



(5) 







Sn. Isabel 



22 



72 



(4) 



78 



(3) 



46 



(1) 





21 



66 



(28) 



68 



(24) 



31 



(4) 



Note. — Figures in ( ) after percentages indicate numbers of fields examined. 

 1 Average of rainfall of haciendas, not of the town. 



