THE SUGAR-CANE MOTH BORER. 



57 



as compared with 20.3 per cent at Audubon Park, where the trash 

 was not burned on any of the fields but one. Comparing this burned- 

 over field with an average of the other stubble fields, we have an 

 infestation of 38 per cent for the burned-over field, while the average 

 infestation of eight unburned stubble fields was 20.2 per cent, with 

 36 per cent as the highest infestation on an unburned field. 



The plantation results in 1917 are in accord with the theory that 

 isolation of fields influences the results of nonburning, using the term 

 " isolation " to mean not only a situation detached from other cane 

 plantings, but one 

 separated from plan- 

 tations where the 

 trash is burned. In 

 a locality in the 

 midst of the sugar 

 parishes, a tj^pical 

 plantation ( d e s i g- 

 natecl A on the dia- 

 gram, fig. 12), front- 

 ing on the Mississippi 

 River and running 

 back to swamp land 

 was not burned over, 

 the trash being 

 plowed under in the 

 fall. This plantation 

 was bordered on the 

 north by a burned- 

 over plantation (B), 

 and on the south by a 

 much smaller planta- 

 tion (BB), a long 

 and narrow strip of 

 land which had also 

 been burned over. But 

 bordering these plan- 

 tations was one on the north (0) in which only part of the trash had 

 been burned, the rest having been plowed under, and one on the 

 south (00) treated in the same way. Plantation A, where the trash 

 had not been burned, while bordered on each side by burned-over 

 areas, was yet the center of a district where much of the trash had 

 been saved. The infestation at A was 22.5 per cent, and at and GO 

 it was 56.9 per cent and 53.6 per cent, respectively. At B — burned 

 over, but between A and O and undoubtedly influenced by the trash 

 saved at those places — it was 49.5 per cent. Plantation BB was over- 



Fig. 12. — Diagram of plantations showing percentages of 

 infestation by the sugar-cane moth borer in relation 

 to nonburning of cane trash. 



