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INSECT 



SURVEY 



BULLETIN 



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College of Agriculture 



University of Illinois 



and Natural History Survey, Urbana, Illinois 



U. S. Department of Agriculture Cooperating 



FOR IMMEDIATE RELEASE 



July 5, 1968 



ILLINOIS INSECT. DISEASE, AND WEED SURVEY BULLETIN NO. 17 

 This series of weekly bulletins provides a generalJ^Dffhoe^ ±h& insect, plant dis- 



ease, and weed situation (fruit and aommeroial vegetables'"e'xc T ep'Q&d) , along with 

 suggested, abbreviated control measures. Each indiyddus^lfpsl^uld check his own 



ummtu ar nam 



fields to determine local conditions. 



INSECTS 



THE LIBRARY OF THE 

 JUL S 1968 



Corn Insects 



IINSVERSIV OF ILLINOIS 



Corn rootworm development is progressing rapidly. This week occasional, early- 

 emerging adults were observed. In addition, between 2 and 3 percent of the root- 

 worm population is now in the resting or pupal stage, and will soon change into 

 adults. Apparently, rootworm development is earlier in western than in eastern 

 Illinois; but, in general, it is now too late to make a basal or cultivator appli- 

 cation of an insecticide in most fields. In most instances, corn-plants breakage 

 and root pruning would be too great to justify this basal application. Also, in 

 most fields, the worms are now big enough to be difficult to kill by late insecti- 

 cide applications. 



Billbugs are damaging late -planted corn; in a few of these problem fields, damage 

 is severe. Billbugs are gray, brown, or black snout beetles (1/5- to 3/4 -inch) 

 that drill holes in the stalk below ground level, usually at or just above the 

 main roots. When the leaves emerge, they have a series of holes in them. The 

 adult snout beetles stay hidden in the soil and under clods during the day, but 

 often move readily from plant to plant at night. Soil treatments with aldrin and 

 heptachlor have never been highly effective against billbugs. 



If damage is severe and treatment indicated, apply 1-1/2 pounds of actual carbaryl 

 (Sevin) as a band spray over the row. 



Corn flea beetles continue to damage occasional, late-planted cornfields that are 

 bordered by grassy areas. These small black beetles (that jump readily when dis- 

 turbed) leave white scratch marks on the leaves. Once corn reaches 10 to 12 inches 

 in height, it can usually grow away from flea-beetle injury. 



If damage is severe and plants are being killed, apply 3/4 pound of carbaryl 

 (Sevin) - -preferred on dairy farms--or 1-1/2 pounds of toxaphene per acre as a band 

 spray over the row. 



The first European corn borer larvae are maturing rapidly, and many of them have 

 already entered the stalk. Development appears to be slightly earlier than normal. 

 Once they have bored into the stalk, insecticides no longer control them. It is 



