54 BULLETIN 740, U. S. DEPARTMENT OP AGRICULTURE. 



and from cane depositing their eggs on the young corn plants as 

 "well as on the cane. 



BURNING CANE TRASH. 



Iii the process of harvesting sugar cane the tops of the plants 

 and the lateral leaves are cut off and left in the fields, forming a 

 quantity of fibrous vegetable matter almost universally called " the 

 trash." (PI. VIII, fig. 1.) A common recommendation has been 

 to burn this debris as soon as it is dry enough, which is within a 

 few weeks after the cane has been cut. Apparently burning would 

 tend to decrease the subsequent infestation by the moth borer, but 

 this has not been found to be the case. Examinations of the trash 

 indicate that comparatively few borers are usually to be found in 

 it, most of them being in the stalks of the cane, which are carted 

 from the field and ground in the mill, thus disposing of the greater 

 number. On the other hand, the trash is a favorable hibernating 

 place for numbers of dipterous and hymenopterous insects, many 

 probably of beneficial species. The eggs of the moth borer are de- 

 posited on the leaves of the cane plants, and these are attacked by the 

 egg parasite Trlcho gram/ma minutwrn. It is probable that these 

 minute beneficial insects are destroyed in great numbers when the 

 trash is burned. 



Louisiana sugar-cane planters have been burning over their sugar- 

 cane fields for many years (PI. IX, fig. 2) , and it has not been found 

 that any reduction in the number of canes infested by the moth borer 

 results. Trash burning and other methods of control formerly recom- 

 mended were thoroughly tried out on a plantation in Louisiana some 

 years ago (see " Immersion and fumigation of infested seed cane," p. 

 49), but without beneficial effect. It is the opinion of the authors, 

 after having made many field observations, that trash burning can 

 not be expected to diminish the number of canes infested, while it 

 may increase the infestation by destroying beneficial insects. An 

 objection to trash burning, admitted even by its advocates, is that 

 ordinarily it is not thoroughly done. The dry leaves which burn 

 readily are consumed, and in the fields are left short scraps of cane, 

 Avhich sometimes contain living borers, even though they have been 

 considerably heated and charred by the fire. It is evident that trash 

 burning, while unquestionably destroying many beneficial insects, 

 frequently fails to destroy the few borers left in the field, because of 

 their protected situation in scraps of cane which do not burn readily. 



When it is remembered that there are four or five generations of 

 borers per year, that about half of the adults are females, and that 

 each female lays an average of 200 eggs, it will be realized that a 

 ven^ few borers passing the winter successfully are sufficient to infest 

 a whole plantation, especially if their parasites have been destroyed. 



