nub i g m 



State 



INSECT 



SURVEY 



BULLETIN 



^«T %/ 



s 'n os 



College of Agriculture 



University of Illinois 



and Natural History Survey, Urbana, Illinois 



U. S. Department of Agriculture Cooperating 



FOR IMMEDIATE RELEASE 



August 18, 1967 



INSECT SURVEY BULLETIN NO. 19 



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 









European corn borer moth emergence has been delayed by the cool weather in the 

 north- central and northern sections. Moths will continue to emerge and lay eggs 

 for at least 3 weeks in those areas. Infestations are expected to be greatest in 

 the northwestern and western sections. 



Although corn borers will deposit eggs on all corn, they tend to concentrate their 

 egg-laying in fields in the late whorl to early silk stage. Treatment is profit- 

 able if there is an average of one or more egg masses per plant. Use 1 pound of 

 actual diazinon or 1 1/2 pounds of actual carbaryl per acre as granules or sprays. 

 Allow 10 days to elapse before making ensilage or stover when using diazinon; 

 carbaryl has no waiting period. Commercial applicators may prefer to use EPN or 

 parathion; they also provide good control of corn borers. Parathion has a 12-day 

 waiting period between treatment and harvest; EPN, a 14-day waiting period. 



The green or yellowish-brown adults of the northern corn rootworm can still be 

 found in many cornfields . In a few fields in the northern two-thirds of the state 

 as many as 10 to 20 per plant are present. These are fields in which no soil in- 

 secticide was applied or in which the insect has developed resistance to the chlor- 

 inated hydrocarbons, aldrin and heptachlor. 



A survey of several hundred cornfields the past two weeks indicates that northern 

 corn rootworm resistance has become more general and that numbers are at a record 

 high. In addition, this year we observed larval damage in several fields of first- 

 and second-year corn. Generally, only continuous corn (third year or more) is 

 damaged and only rarely a field of first- or second-year corn. Most fields have 

 now pollinated, and silk feeding is not important even though the beetles are feed- 

 ing on and damaging ear tips slightly. In general, treatment at this time will 

 not be profitable, except in late-maturing fields where pollination may still be 

 affected by silk feeding. 



Western corn rootworm adults were found for the first time this week in Bureau and 

 and Carroll counties. They have now been identified in eight new counties this 

 year and more are expected. By 1968 this insect will probably be present through- 

 out the northern half of the state. The western corn rootworm cross-mates with 



