'TTyy. '"y Cooperative Extension Service, University of 



Illinois College of Agriculture in Cooperation with 

 the Illinois Natural History Survey and U. S.D.A. 



FOR IMMEDIATE RELEASE June l8, I965 



INSECT SURVEY BULLETIN NO. 9 



This is the ninth 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. 



European corn borer moths have been somewhat inactive because of cool 

 temperatures. They have remained in weed patches and other protected areas. With 

 the first warm, calm nights, moths will become active and deposit eggs. During 

 the past week, the corn has been growing and is now becoming more favorable for 

 borer survival. 



Apparently egg laying is nearly complete south of a line from Carthage to 

 Macomb to Champaign. From 25 to 50 percent of the corn in much of this area is now 

 acceptable to moths for egg laying. Thus the few eggs yet to be laid will be 

 scattered over many fields rather than concentrated in a few. 



From this line north to a line from Rock Island to LaSalle, moth emergence 

 is practically complete, but a few moths will be laying eggs until about July 1. 

 In many areas there is no early corn; here borers will lay eggs en the short corn, 

 weeds, flowers and small grains, and survival will be low. But in other localities 

 some fields are much more mature than others in the vicinity. Watch these fields, 

 as moths may concentrate their egg laying here. 



In the area north of the line from Rock Island to LaSalle, there are still 

 some moths to emerge and egg laying will probably continue until July k. Although 

 the situation does not appear serious, observe the most advanced fields closely for 

 the next two weeks. 



To decide whether an insecticide can be profitably applied, measure the 

 tassel ratio of the field and count the percent of plants with recent whorl leaf 

 feeding. To determine the tassel ratio, measure the height of the plant with leaves 

 extended; split the stalk open and measure from the tip of the developing tassel to 

 the base of the plant. Divide the tassel height by the plant height, and multiply 

 by 100. This figure is the tassel ratio. If the tassel ratio is at least 35 

 (preferably kO to k^) and at least 75 percent of the plants show recent whorl feed- 

 ing, then treatment is justified. Use 1 pound of actual diazinon in granular form 

 per acre or 1 l/2 to 2 pounds of carbaryl (Sevin) as granules. For spraying, use 

 the same amount of actual insecticide per acre, and direct the spray to the upper 

 third of the plant. Aerial applications should be granules, not sprays or dusts. 

 Follow the label precautions in harvesting and feeding treated corn. DDT can be 

 used as granules or sprays, but not on or adjacent to dairy farms. 



Black cutworms continue to be a problem in north-central Illinois, and 

 we have had occasional reports of this pest from northern Illinois. Continue to 

 watch for spots in fields where stands suddenly appear thin. Look for signs of 

 this pest cutting off the corn. 



JSH22 



