^£s^ 7 



FOR IMMEDIATE RELEASE June 12, 196^ 



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. 



Corn borer pupation is nearly complete throughout Illinois; moth emergence 

 is progressing rapidly, and the moths have begun to deposit eggs on the most ad- 

 vanced corn. 



The area where corn is most likely to be damaged by corn borer lies west 

 of a line from Rockford to Joliet and north of a line from Joliet to Pittsfield. 

 Here borer development is about normal, while corn development is slightly below 

 normal south of Highway 6. The result is fewer borers and less damage. With warm 

 nights, egg-laying should peak in about 10 days in this area. However, in the 

 northern section (north of Highway 6), borer development may be slightly slower than 

 normal, but corn development is about normal. Here more borers will survive and, 

 peak egg-laying will occur in about two weeks. 



Cool nights and windy weather would postpone egg- laying and increase the 

 damage potential in the threatened areas . 



Watch carefully for borers in the more advanced fields of corn during the 

 next two or three weeks. To decide whether to use insecticides, measure the tassel 

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

 1 +0- i +5) and at least 75 percent of the plants show recent whorl leaf feeding, then 

 treatment is justified. Use 1 pound of DDT or 1 l/2 to 2 pounds of carbaryl (Sevin) 

 per acre as granules. For spraying, use 1 l/2 pounds of DDT 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. 



Black cutworms and wireworms continued to damage corn. Small, half- grown 

 cutworms will feed for several more days; they can still be found along with larger 

 sizes that have about finished feeding. 



If small worms are still plentiful and you feel that insecticides are 

 justified, use l/2 pound of dieldrin or 3 pounds of toxaphene per acre as a spray. 

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

 acre as possible, and cultivate immediately to cover the insecticide. 



If replanting becomes necessary because of wireworms, either leave the 

 old stand and straddle the rows when replanting or, if disking up the old stand, 

 broadcast aldrin or heptachlor at 1 l/2 pounds per acre before disking or use 1 

 pound per acre as a row application during planting. Where replanting, select a 

 hybrid that will mature before frost. 



