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



age annual infestation has been determined to be 58.2 per cent, or 

 over half the canes infested. In 1912 the general average was 50.4 

 per cent, in 1913 it was 52.4 per cent, in 1914 it reached the high 

 figure of 73.9 per cent, while in 1915 the average sank to 51.5 per 

 cent. The average was again high in 1916, being 75.5 per cent, but 

 in 1917 it was 48.8 per cent, the lowest during the six years. In 

 some localities an infestation of 100 per cent is sometimes reached, 

 or all canes infested, while in others the damage may be 30 per cent 

 or lower. 



Continuous observations have not been made in Texas, but in the 

 lower Eio Grande Valley, to which the borer is limited at present, 

 casual inspections usually reveal an infestation of nearly 100 per 

 cent. 



VABIATIONS IN INFESTATION. 



The infestation of different fields of sugar cane in the sugar-pro- 

 ducing region varies from a low percentage to 100 per cent, or every 

 cane infested. Conflicting opinions are held by different planters 

 as to the infestation of the different varieties of cane and the in- 

 festation in different years of growth. It has not been found that 

 one common variety is more resistant to the moth borer than an- 

 other, or that plant cane is more infested or less infested than first 

 or second year stubble. 1 Another popular belief is that cane grown 

 on sandy land is likely to be more heavily infested than cane grown 

 on heavy soil. Examinations do not show that this is true, but the 

 belief may have some basis, because it has been found that moths can 

 emerge more readily from canes planted in sandy soil than from 

 those planted in clay soil. The idea is also held that land treated 

 with stable manure or cottonseed meal will be more heavily infested, 

 but the data on the subject are insufficient to warrant any conclusion. 



MANY LARVAE CRUSHED IN THE MILL. 



The greater number of moth borers in the larva stage in the late 

 fall and early winter which would otherwise hibernate remain in the 

 stalks of cane after they are cut. An examination of bored stalks 

 at Audubon Park just before grinding yielded the information that 

 38 per cent of the stalks contained borers. When the stalks arc 

 ground in the mill these larvae are crushed with the cane, leaving 

 only such borers as may be in the stubble, seed cane, scraps of cane 

 left about the plantations, cane tops, and Johnson grass and other 

 grasses to start the infestation the following year. 



1 In 1918, however, 10,000 stalks of cane were examined on a group of six plantations, 

 (he examinations being well distributed and evenly divided between plant and stubble cane. 

 It was found that the general average for plant cane on each plantation was invariably 

 higher than for stubble, though there were wide variations among certain fields and parts 

 of fields, both of plant and stubble cane. Examinations on a much smaller scale, made 

 in previous years, did not indicate any difference in favor of cither plant or stubble. 



