58 BULLETIN 746, TJ. S. DEPARTMENT OP AGRICULTURE. 



looked and the infestation is not known, but at two places in the 

 vicinity, D and DD, both burned over, the infestation was 77 per cent 

 and 75 per cent, respectively. The map will convey a more accurate 

 idea of the situation than any further explanation, but the following 

 points should be noted : At the two burned-over plantations, D and 

 DD, farthest away from unburned fields, the infestation was high, 

 about 75 per cent. At the two partly burned plantations, C and CC, 

 it was medium, about 55 per cent. At the burned-over plantation Z>, 

 bordered on each side by unburned or partly burned fields, it was 

 also medium, 49.5 per cent. At plantation A, not burned and the 

 center of a nonburning region, the infestation was the lowest of all, 

 only 22.5 per cent. 



It is evident that a plantation must be considered as a unit in 

 determining the infestation. The former custom was to consider a 

 field as a unit, to which there is the objection that the moths of the 

 borer can fly readily and doubtless reinfest areas in which the para- 

 sites have gained the ascendency. Although a comparison of fields 

 at Audubon Park is not unsatisfactory, it is true that the fields there 

 are small, and they are not surrounded by vast stretches of cane and 

 cornfields which are typical of the sugar parishes. 



The results in 1917 indicate that nonburning will be effective on 

 isolated areas of any size and on nonisolated areas so large that the 

 bordering burned-over fields will have little effect on the general 

 infestation. An illustration of nonburning on a single narrow 

 plantation surrounded by burned-over areas was obtained in 1917. 

 In this case nonburning was apparently of no benefit, the infestation 

 being slightly, if any, lower than at a neighboring place. Yet the 

 benefit to the land of plowing under the trash is considerable, and 

 as it is only by degrees that the new practice will become established 

 no planter should hesitate to practice nonburning because his neigh- 

 bor refuses to do so. 



A planter who has plowed under his trash tells us that it maintains 

 the tilth of the soil from year to year, and the difference between the 

 condition of the soil where trash has been plowed under and where 

 it has been burned is immediately perceptible. Where the trash is 

 plowed under the soil is left open and porous and is enriched by the 

 nitrogen and other fertilizing elements of the decaying vegetation. 

 (See PL IX, fig. 1.) 



The work of plowing out the trash in the spring is regarded by 

 some planters as so great that they refuse to leave it on the fields 

 unburned. At the Sugar Experiment Station the process of caring 

 for the trash, quoting Mr. W. T. Taggart, assistant director, is as 

 follows : 



In plowing under cane tops, especially on land where stubble is to be held 

 for the following year, the work must be done in such a manner as not to 



