332 AisnsnjAii report Smithsonian iNSTiTDnoN,, 1942 



control of grasshoppers, Mormon crickets, find armyworms has been 

 greatly increased in scope and efficiency by the invention and wide 

 use of motorized equipment (pi. 10) . The invention and use of power 

 bait-mixing machines, traction and power bait spreaders, the use of 

 motor trucks for hauling bait, and the adaptation of airplanes for its 

 rapid application, especially on terrain not readily treated by ground 

 equipment, have all contributed wonderfully to the practicability and 

 effectiveness of large-scale control operations against these insects. 



CHEMICAIi AND MECHANICAL BARRIERS 



The habits of certain of the insects attacking cereal crops are such 

 that chemical or mechanical barriers, or a combination of both, may 

 be used to good advantage in their control. The chinch bug is a good 

 example. Tliis insect is one of the worst pests of corn in the main 

 Corn Belt. Wlien weather conditions are favorable it develops in 

 enormous numbers in the small grains during the spring and early 

 summer, sometimes seriously injuring considerable acreages of them. 

 The small grains usually ripen before the spring brood of bugs attains 

 the winged or adult stage and the immature bugs then migrate on 

 foot from the small-grain fields into the nearby fields of young corn. 

 If this migration is not stopped immediately the complete destruction 

 of the corn may be only a matter of days. Fortunately for the farm- 

 ers, however, the bugs must migrate by crawling instead of flying; 

 hence, it is possible to stop them effectively by means of a barrier of 

 some kind (pi. 12). One of the best barriers is a line of coal-tar 

 creosote placed across their line of advance, applied directly on a 

 smooth, hard -packed low ridge of earth or on a fence about 2 inches 

 high made of heavy paper. The latter method is the more efficient. 

 Post holes to serve as traps are then dug about every 20 feet along the 

 side of the barrier toward which the bugs are migrating. Creosote is 

 very repellent to chinch bugs, and they will not cross the barrier line as 

 long as it is kept in good condition. Instead, they travel in streams 

 along it until they fall into the post holes where they are killed. With 

 the prompt installation and proper maintenance of these barriers the 

 corn can be completely protected. 



But here again we encounter another instance of the far-reaching 

 effect of the present war. It has created a scarcity of coal-tar creosote 

 that may make this material difficult, if not impossible, to obtain for 

 chinch-bug control. Anticipating this situation, however, both State 

 and Federal entomologists have been experimenting with possible 

 substitutes and have succeeded in finding several very promising ones. 

 Some of these may prove to be even better than creosote and applicable 

 to the corn itself, in case of need, as well as to barriers. 



Before repellent chemicals came into use for chinch-bug barriers 

 a simple mechanical type of barrier was widely used, consisting of 



