56 BULLETIN 746, U. S. DEPARTMENT OF AGRICULTURE. 



the plat on "which it was burned in the fall by a plantation roadway 

 about 20 feet wide. Needless to state, these conditions were not of 

 the best for the experiments. It would have been better if each 

 plat had been comparatively isolated from other plats of cane so 

 that there would have been no danger of the insects going from one 

 plat to another. 



It will be noted that the infestation at the end of May was almost 

 negligible in all plats, but even then the least injury was in the plat 

 where trash was plowed under in the spring. By October 28 the 

 most conspicuous injury ("dead hearts" and large plants killed) 

 was small, but the difference between the plats subjected to different 

 treatments is notable. Again, the smallest number of killed plants 

 (3) was found in the plat where trash was left on the field in the 

 winter and plowed under in the spring. Fall burning gave as many 

 as 38 plants killed. In the plats where the trash was raked to the 

 headland in the spring, and where it was burned in the spring, there 

 were 12 and 6 dead plants, respectively — several times more than 

 where the trash was plowed under in the spring. A few days later, 

 when the cane was cut, a careful examination was made of over 600 

 canes in each plat. Where the trash was burned in the fall the 

 infestation was nearly 84 per cent, but where the trash was plowed 

 under in the spring it was only about 46 per cent. The experiments 

 in raking the trash to the headland, and in burning it in the spring, 

 gave about 65 and 69 per cent, respectively. From these experi- 

 ments spring burning seems to be better than fall burning, and plow- 

 ing the trash under in the spring better than either. (PI. VIII, fig. 

 2.) Raking the trash to the headland, for some unknown reason, 

 did not give as good results in 1914 as it did in 1913. 



Extensive experiments on plantations in Louisiana were carried 

 on in 1915, 1916, and 1917. During 1915 and 1916 the results were 

 negative, the infestation being about the same on fields where trash 

 was not burned as where it was burned. The fields not burned were 

 usually in the midst of other fields which had been burned over. 

 Yet in 1916, when the trash was not burned except on one field at 

 Audubon Park, the infestation was much lower there than anywhere 

 else in the State, with the exception of two places which had been 

 flooded. The average infestation in Louisiana for 1916 was 75.5 per 

 cent, while the infestation at Audubon Park was only 38.3 per cent. 



The reason for the difference between the results on plantations 

 and those at Audubon Park was not understood until it was sug- 

 gested in 1917 by Mr. W. G. Taggart that the relative isolation of 

 the fields at Audubon Park had prevented the reinfestation of the 

 unburned fields by moths flying from other plantations. This ex- 

 planation seems to be correct, and the latest results tend to confirm 

 it. The average infestation in Louisiana in 1917 was 45.8 per cent, 



