FOR IMMEDIATE RELEASE June 5> 196U 



INSECT SURVEY BULLETIN NO. 8 



This is the eighth in a series of weekly bulletins on the general insect 

 situation in Illinois (fruit insects excepted), prepared by entomologists of the 

 University of Illinois College of Agriculture, Illinois Natural History Survey and 

 cooperating agencies. It is designed to forewarn people in Illinois of impending 

 changes in insect activity and to suggest abbreviated control measures. These re- 

 ports indicate only general trends. Each individual should check his own fields to 

 determine local conditions. 



Armyworms matured rapidly in the area south of Route 9 this past week. 

 With pupation, worm populations decreased. Small worms are still present in a few 

 fields, but they are the exception. Numbers are also being lowered by disease and 

 parasites. Except for a few unusual fields, treatment in this area should cease. 

 Thick stands of wheat in the area north of Route 9 still have l/2- to 2/3-grown 

 worms, and occasional fields have threatening numbers. 



We have had several reports that armyworm control apparently was not 

 effective. It is difficult to determine immediately. Most insecticides kill army- 

 worms slowly. Only about 25 percent of the worms ordinarily contact the insecticide 

 in the first 2U hours. Cool weather has also slowed down kill. For these reasons, 

 do not try to determine the effectiveness of sprays for 96 hours after application. 



Black cutworms rate the "insect of the week" award. Infestations are 

 scattered throughout the state. Worms are not predominantly one size, but vary 

 within a field from small to full grown. Thus the damage will probably continue 

 into the week of June 8. 



Many plants are now being cut below the growing point and will not recover. 

 If 10 percent or more of the plants are being cut below the growing point, an appli- 

 cation of l/2 pound of dieldrin or 3 pounds of toxaphene is warranted. Direct the 

 spray into the soil at the base of the plant. Use as much water per acre as 

 possible. Cultivate immediately to cover the insecticide. 



Insecticides commonly fail to give a high degree of control, since the 

 worms are below the soil surface where they can not be reached with sprays. Also, 

 as the worms become larger, they are naturally harder to control. If the field has 

 been destroyed and insecticides are not to be used, either consider replanting with 

 soybeans or, if replanting with corn, delay a few days to allow the worms to mature, 

 and use a hybrid that will mature before frost. 



Wireworms continue to damage corn in some areas. If replanting is 

 necessary, either leave the old stand and straddle the rows to replant or, if disk- 

 ing up the old stand, broadcast aldrin or heptachlor at 1 l/2 pounds per acre be- 

 fore disking or use 1 pound per acre as a row application at planting. 



Corn borer moth emergence is about 75 percent complete in south-central 

 Illinois and ranges from 25 to 75 percent in the central and north-central sections 

 and from 10 to 50 percent in the northern part. 



Corn borer development is comparable with that of other years, but corn 

 development is slightly behind schedule. It might therefore appear that potential 

 corn borer survival will be low this year. However, dry weather could delay moth 

 emergence and egg- laying and thus favor survival of borers. Therefore, as usual, 

 the need for insecticide control in the most advanced fields in western and north- 

 western Illinois can not be determined until egg hatch, which will occur between 

 June 25 and July 5. 



