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 typical 
plantation ( d e s i g- 
nated 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 (Z?), 
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 C and 00 
it was 56.9 per cent and 53.6 per cent, respectively. At B — burned 
over, but between A and 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. 
