326 ANNUAL REPORT SMITHSONIAN INSTITUTION,, 1942 



relation to the cultural methods required for the crop or crops on 

 which it feeds. With this knowledge as a basis we are in a position 

 to determine what measures can be utilized in its suppression, such as 

 changes in time of planting the crop; changes in the succession of 

 crops in the rotation; best tillage methods and best time to apply 

 them ; timely destruction of crop residues ; use of mechanical devices, 

 barriers, and insecticides; and tlie discovery or development of re- 

 sistant varieties of the crops attacked. 



CULTURAL CONTROL MEASURES 



Variations in the cultural procedures ordinarily followed in growing 

 the particular kind of grain attacked may often be utilized in pre- 

 venting injury to that crop by certain insects. Control measures of 

 this type are especially desirable because they add little or nothing to 

 the expense of growing the crop. One of the most effective means of 

 preventing the hessian fly (pis. 1-3) from attacking winter wheat, for 

 instance, is to delay the sowing of the crop in the fall just long enough 

 so that it does not come up until the fall flight of the insect is past. 

 Moderately late plantings of corn are less seriously damaged than early 

 plantings by the rootworm or "budworm" (pi. 4) in the southeastern 

 States, and by the European corn borer in the northeastern States. 

 Again, midseason (May) plantings of corn in southeastern Texas are 

 better able to survive the attack of the sugarcane borer, a serious pest 

 of corn in that area, than early or late plantings, because they escape 

 the first brood and attain enough growth before the advent of the 

 second and later broods to withstand them more successfully than late 

 plantings do. 



The proper disposal of crop residues is often helpful in the control 

 of certain insects, and highly important in the control of others. The 

 European corn borer survives the winter in the full-grown caterpillar 

 stage, chiefly in the stalks of corn and coarse-steimned weeds. In late 

 spring or early summer the caterpillars change to moths which fly 

 to the new corn for egg laying. Complete disposal of the plant resi- 

 dues in which the borers overwinter, by plowing them under (pi. 5), 

 feeding them to stock, or burning them before the spring emergence 

 of the moth, is one of the most important control measures for this 

 insect. The sugarcane borer has similar habits in sugarcane, sorghum, 

 and corn, except that the warmer climate along the Gulf coast where 

 it occurs causes the adult moths to emerge earlier in the spring; hence 

 fall or winter disposal of the residues of these crops is helpful in the 

 control of this insect also. In the case of several wheat-infesting 

 insects, e. g., the hessian fly, jointworm (pi. 4), strawworm, and saw- 

 fly, the plowing under of the wheat stubble during the summer or 

 early fall prevents tlieir emergence to infest the new crop, or to breed 



