-3- 



rotations involving only 1 year of corn may be required. However, the resistant 

 strain of northern corn rootworms may become a problem on second-year corn, much 

 as the western corn rootworms are now. 



In addition to crop rotation, early planting may help minimize root damage by 

 corn rootworm larvae and pollination damage by the adults. However, early plant- 

 ing may increase corn borer problems . 



Although several insecticides are labeled for corn rootworm control entomologists 

 of the University of Illinois Cooperative Extension Service and the Illinois Natu- 

 ral History Survey suggest the following materials for the most-effective control 

 of rootworm in Illinois. These rates are based on row length, not width. 



For Planting Application 



Furadan (if label approval is granted) 1 pound per acre 



Buxten 1 pound per acre 



Dasanit 1 pound per acre 



Dyfonate 1 pound per acre 



Phorate 1 pound per acre 



These materials were used in Illinois in 1968 at the rates shown. To reduce 

 costs, lower rates of application have been suggested. Lower rates will likely 

 reduce effectiveness, particularly with heavy infestations. 



For Basal Application in June 



Diazinon 1 pound per acre 



Disulfoton 1 pound per acre 



Parathion 1 pound per acre 



Phorate 1 pound per acre 



Carbaryl 2 pounds per acre 



Many of the registered organic -phosphate insecticides- -and carbamate insecticides 

 when applied at planting time --kill only 40 to 75 percent of the rootworms. With 

 light infestations of corn rootworms, this provides practical control; although 

 not as effective on early planted corn as on that planted later, they still did 

 an acceptable job in Illinois during 1968. However, in fields with moderate-to- 

 heavy infestations, the more -effective insecticides are needed to give a practical 

 degree of control. 



Applications of insecticides approved for use during cultivation in late May to 

 mid- June are equally effective. The insecticide is directed at the base of the 

 plant; for best results, there should be some soil cover. These basal applica- 

 tions can be made when convenient. But to avoid bad weather, do not wait until 

 the last minute. 



The insecticides listed for rootworm control at planting may be adversely affected 

 by heavy rainfall. The control of corn rootworm may be less effective when these 

 insecticides are applied to early rather than later-planted corn, because of ex- 

 posure to greater amounts of rainfall. 



Extreme drought conditions may also decrease the effectiveness of the insecticide. 

 This could be particularly important in the use of basal applications to control 

 rootworms. For this reason, late May to mid- June applications are encouraged, in 

 order to take advantage of normal rainfall patterns. 



