\f Cooperative Extension Service, University of 



Illinois College of Agriculture in Cooperation With 

 the Illinois Natural History Survey and U.S.D.A. 



FOR IMMEDIATE RELEASE August 5 1966 



INSECT SURVEY BULLETIN NO. l6 



This sixteenth weekly bulletin on the general insect situation in Illinois 

 (fruit insects excepted), prepared by entomologists of the University of Illinois 

 College of Agriculture, Illinois Natural History Survey and cooperating agencies, 

 reports general trends in insect activity and suggests abbreviated control measures. 

 Each individual should check his own fields to determine local conditions. 



Present Farm Insect Problems 



Corn leaf aphids continue to cause concern in much of the northern half of 

 Illinois. In general, populations have peaked and are now beginning to decline due 

 to predators, parasites and disease. Lady beetles, syrphid flies, aphis lions and 

 parasitic wasps are reducing aphid numbers. Aphids normally tend to produce winged 

 forms and leave plants and disappear shortly after tassel emergence. It is only in 

 occasional fields that a population will remain high. 



In some fields (particularly those maturing early) the aphids have almost 

 completely disappeared. In other fields (especially mid- to late-maturing fields) 

 they have completely covered the upper leaves and are dropping down and coating the 

 lower leaves and silks. 



These aphids suck the sap from the corn plants, causing barren plants. 

 Unfortunately they cause this damage while the corn is still in the whorl stage. 

 Therefore, in most fields it is now too late to get maximum benefits from control 

 neasures . 



If a field is severely infested with healthy aphids (25 percent or more of 

 the plants coated) and few predators are present, treatment may still be profitable, 

 especially if soil moisture is low- 



acre. 



For control, apply 1 1/1» pounds of malathion or 1 pound of diazinon per 

 Allow 10 days between application and harvest when applying malathion. 

 Diazinon sprays can be applied until the day of harvest. 



European corn borer moth emergence is complete in the southern section of 

 ihe state and well along in the central section. In the northern section, only 15 

 to 30 percent of the moths have emerged. Moth flight and egg laying will continue 

 For another week or two in the southern section and for another three or four weeks 

 Ln the northern section. Second-generation moths will concentrate egg laying in the 

 Late-maturing fields, and it is these fields that will bear watching. 



Infestations are expected to be greatest in an area two or three counties 

 ride along the west side of the state from St. Louis northward and in the extreme 

 lorthern tier of counties. The infestation is expected to be most severe just south 

 >f Rock Island. Populations of second-generation corn borers are expected to be low 

 in much of the central and particularly the east-central section. A survey of the 

 southern section showed first-generation populations to be light; we do not expect 

 1 generally heavy second-generation population. 



