25 



INJXniY TO FIELD CORN. 



The close relation between the depredations of the bollworm upon 

 corn and cotton has necessitated a careful study of the insect in the 

 former as well as in the latter crop. The characteristic injury to corn 

 has been described in the preceding pages. Although bollworm 

 injury to cotton greatly eclipses that to corn, the loss occasioned by 

 its presence each year in probably more than 75 per cent of the corn 

 ears and by the additional damage resulting from ferments, molds, 

 and rain admitted through the exit holes of the larvee is considerable. 



Injury to young corn by the first brood of boll worms is seldom 

 serious. A notable exception, however, is presented in the case of 

 extremely severe injury inflicted upon young corn by this brood at 

 Victoria, Tex., during the spring of 1905. Mr. W. W. Yothers, of 

 the Bureau of Entomology, investigated this outbreak quite thor- 

 oughly during the latter part of May. It was found that severe 

 injury had been inflicted over quite an extended area, necessitating 

 the replanting of a considerable portion of the corn acreage to June 

 corn or cotton. It was estimated by Mr. Yothers and others that the 

 total yield in the vicinity of Victoria would be reduced fully 40 per 

 cent on account of bollworm injury. Severe injury to corn was re- 

 ported also in Shackleford County, Tex., but its extent was not 

 definitely ascertained. 



In 1905 numerous observations in northern Texas and Indian Ter- 

 ritory showed the number of eggs and larvae to be comparatively few 

 upon corn until about July 1. After this date, however, from 90 to 

 100 per cent of the corn ears were found to be infested. No serious 

 injury to corn was reported in 1906, but observations showed that 

 practically complete infestation of corn ears was attained during 

 the latter part of the summer. 



The chief means of reducing bollworm injury to corn is by thor- 

 oughly breaking, during the fall and winter, all land likely to contain 

 hibernating pupa?, a procedure which the writers have stated to be an 

 important part of the cultural system in reducing bollworm injury to 

 cotton. The practice of having children and plow hands destroy 

 all larvae noticed in the buds of young corn plants is commendable. 



RESULTS OF POISON EXPERIMENTS. 



During 1904 poison experiments were conducted at Ladonia, Paris, 

 and Cooper, Tex. At Ladonia and Paris the experiments were con- 

 ducted directly by the writers, while at Cooper the work was carried 

 out by Mr. N. P. Robertson, of that place. The dusting method was 

 used exclusively. The Paris green was mixed with fine, air-slaked 

 lime at the rate of 1 pound of Paris green to 4 pounds of lime, and the 



290 



