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INSECT 



SURVEY 



BULLETIN 



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ate / County 



Local Groups 



College of Agriculture 



University of Illinois 



and Natural History Survey, Urbana, Illinois 



U. S. Department of Agriculture Cooperating 



FOR IMMEDIATE RELEASE 



July 12, 1968 



ILLINOIS INSECT, DISEASE, AND WEED SURVEY BULLETIN NO. 18 



This series of weekly bulletins provides a general look at the insect, plant 

 disease, and weed situation (fruit and commercial vegetables excepted) , along 

 with suggested, abbreviated control measures. Each ■,J-^& l &3v$' should check his 



own fields to determine local conditions. 



INSECTS 



Corn Insects 



JUL 



r> r) W* 



ft.U»»* 



" jut 17 1968 



First-generation European corn borers have begun to pupate in the southern half 

 of Illinois. Pupation is almost complete in the southernmost counties; moth 

 emergence has begun. Watch for whorl damage to late corn by the last week of 

 July. 



In south-central Illinois, pupation ranges from 10 to 40 percent in field corn; 

 moth emergence will begin in late July, In early August, watch for feeding on 

 corn that is in the late-whorl to early-silk stage. 



Second-generation infestations in late field corn can be handled in the same way 

 as the first -generation problem. If 75 percent of the plants have whorl-leaf 

 feeding, apply carbaryl or diazinon granules. If the corn has tasselled, look 

 for egg masses. If the average is about 1 per plant, apply an insecticide when 

 a few eggs have begun to hatch. 



A survey this week of the most mature fields in the area between highways 40 and 

 50 revealed that first-generation borer populations ranged from 25 to 90 per 100 

 plants- -100 mature borers per 100 plants represents a 3-percent decrease in yield. 

 It is too late to control this first generation; with these low numbers, it might 

 not have been profitable anyway. 



Southwestern corn borer is present in several southern Illinois counties. Poten- 

 tially, it is a more serious corn pest than the European corn borer. Fortunately, 

 it does not yet overwinter too successfully in our climate, because its origin 

 was Mexico or Arizona. However, it appears to be slowly adapting to Midwestern 

 conditions. 



A random field survey in the four southernmost counties revealed an average of 

 10 to 30 first-generation southwestern corn borers per 1,000 stalks of corn. 

 This is probably the highest infestation ever in Illinois. 



