INSECT 



SURVEY 



BULLETIN 





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>tate 



County / Local Groups 



College of Agriculture 



University of Illinois 



and Natural History Survey, Urbana, Illinois 



U. S. Department of Agriculture Cooperating 



Th'E L AflfflFTlJE 



JUL 2 6 57 



FOR IMMEDIATE RELEASE 



ff . July 21, 1967 



INSECT SURVEY BULLETIN NO. 15 



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

 (fruit insects excepted), along with suggested, abbreviated control measures. Each 

 individual should check his own fields to determine local conditions. 



Corn Insects 



Corn leaf aphid populations did not increase greatly this week. In the west- 

 southwest section, populations were decreasing in fields that were in the polli- 

 nating stage. In other areas, populations remained low. Insidious flower bugs 

 (resembling a miniature chinch bug) are very abundant in the whorls and tassels 

 of corn this week; this predator and others like syrphid fly maggots, parasitic 

 wasps, lady beetles, and aphis lions are helping to hold aphids in check. 



Early treatment of aphids is best. Check corn that is in the late-whorl to polli- 

 nating stage; if 15 percent or more of the plants are heavily loaded with aphids, 

 treat immediately. After pollen shed, aphid populations usually decline; much of 

 their damage has already been done. Unless the corn is under stress from low mois- 

 ture, fertility, etc., treatments after pollen shed are disappointing. 



Spray treatments by ground or air with 1 pound of malathion or diazinon per acre 

 will control the aphids. When using malathion, allow 5 days between treatment 

 and harvest for grain, ensilage, or stover. There is no waiting period between 

 treatment and harvest for grain when using diazinon, but allow 10 days to elapse 

 before making ensilage or stover. If corn is still in the late-whorl stage, seed 

 producers may prefer to use 1 pound per acre of either diazinon or phorate (Thimet) 

 as granules. To avoid potential hazards to detasselers, use phorate only on male- 

 sterile corn. 



Western corn rootworm adults began emerging this week in the limited area of in- 

 festation in the western section. Northern corn rootworm adults are beginning to 

 emerge in northern and central sections. About 51) percent of them have now reached 

 the pupal (resting) stage. These green beetles can be found in corn in southern 

 sections, but they become more abundant as you go northward. They are most often 

 found in fields where corn has been grown consecutively for 5 or more years. 



Southern corn rootworm adults are abundant in many cornfields, particularly in 

 the southern half of the state. A few fields were damaged by the larvae of the 

 southern corn rootworm feeding on the roots and boring into the underground portion 

 of the stem. The adults feed on silks and, if abundant during silking, will reduce 

 kernel set. 



