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COLLEGE OF 



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HISTORY SURVEY 



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URBANA, ILLINOIS 

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MSEC! WEED & PLANT DISEASE SURVEY BULLETIN 



XTE/COUNTY/LOCAL GROUPS/U.S. DEPARTMENT OF AGRICULTURE COOPERATING 



FOR IMMEDIATE RELEASE 



No. 18, July 30, 1971 



CORN INSECTS 



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

 disease situation (fruit and commercial vegetables excepted) , along with suggested, 

 abbreviated, control measures. Each individual should, check his own fields to de- 

 termine local conditions. _ 



INSECTS „ **»* 



**G 1 W71 



European corn borer . Second-generation moths are laying eggs and trft»"i*atch is progress- 

 ing rapidly in the southern sections of Illinois. Moth emergence in the central areas 

 is well underway, and egg-laying has begun. In the northern section, pupation reached 

 52 percent and emergence 24 percent this week. Peak egg-laying will probably not occur 

 for another week in central Illinois and 10 days in northern Illinois. Egg-laying could 

 continue for two weeks or more. Cool weather has slowed development. Higher than nor- 

 mal populations of first -generation borers in southwestern and western Illinois have 

 increased the possibility of corn damage by second-generation borers in these areas. 



This is the time to check late-maturing fields for egg masses and feeding in the south- 

 ern half and western sections of Illinois. Determine whether treatments are needed. 



The moths will deposit eggs on corn at any stage of its development, but fields of late- 

 planted corn in the late-whorl to early silk stage are usually preferred. Look for egg 

 masses or small, newly hatched larvae. Treatments should be made now in southern Illi- 

 nois. It is still too early to apply insecticides in the central and northern sections. 



To determine whether treatment is necessary look for egg masses or whorl feeding. If 

 the average is one or more eggs masses per plant, apply an insecticide after a few eggs 

 have hatched. If the corn is in the whorl stage and if 75 percent or more of the 

 plants are showing recent whorl feeding, apply carbaryl (Sevin) or diazinon granules. 

 Aerial sprays on tasseled corn are effective; but on whorl -stage corn, aerial applica- 

 tions should be granules not sprays. Use 1-1/2 pounds of carbaryl (Sevin) , 1 pound of 

 diazinon, or 1/2 pound of parathion per acre. (Allow 10 days for diazinon and 12 days 

 for parathion between application and silage removal.) Parathion should be applied 

 only be experienced applicators . No waiting period is required for carbaryl. 



Corn rootworms . The emergence of northern and western adults is progressing very rap- 

 idly. Beetles are feeding on the silks in many corn fields in northwestern Illinois. 

 If the rootworm beetles are numerous, they can reduce pollination. Control is recom- 

 mended only if a field is less than 50-percent silked and there are 5 or more beetles 

 per plant. 



A survey of adult rootworm populations was conducted in thirty Illinois counties this 

 week. The rootworm species surveyed include the tan or pale-green northern ones, the 

 yellow- and black-striped western ones, and the 12-spotted southern rootworms, also 



