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X^n. '7 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 k, 1965 



INSECT SURVEY BULLETIN NO. 7 



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

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

 versity of Illinois College of Agriculture, Illinois Natural History Survey and co- 

 operating agencies. It is designated to forewarn people in Illinois of impending 

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

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

 mine local conditions. 



Chinch hug adults prefer open thin stands of grain; they have had a wide 

 selection of fields this year and until recently they were diluted over a large acre- 

 age. But as growth continued and the ground became more shaded, the adults moved to 

 field borders, low spots, drill skips, and other thin open spots. Here they have 

 been laying eggs. In most instances the newly hatched nymphs are being killed by 

 beating rains. As the adults die and the rains kill the tiny nymphs, our chinch bug 

 potential problem decreases. There undoubtedly are isolated areas that were missed 

 by the recent rains. In these areas chinch bugs may be a problem, and migrations 

 from grain to corn may take place later. 



Corn borer egg-laying is complete in the southernmost counties. Counts in- 

 dicate that 1 to 3 percent of the fields in the southern tip of the state would profit 

 from protection. These, of course, are the most advanced fields. If a field indi- 

 cates a need for insecticide protection, now is the time. 



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 feed- 

 ing. To determine the tassel ratio, measure the height of the plant with leaves ex- 

 tended; 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 3.00. 

 This figure is the tassel ratio. If the tassel ratio is at least 35 (preferably ^0 

 to 45) and at least 75 percent of the plants show recent whorl feeding, then treat- 

 ment 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 pre- 

 cautions in harvesting and feeding treated corn. DDT can be used as granules or 

 sprays, but not on or adjacent to dairy farms. 



In northwestern and western Illinois, pupation is rapidly nearing comple- 

 tion. In some instances up to 50 percent of the moths have emerged. However, some 

 of the wintering larvae have not yet pupated. This means that some moths will still 

 be laying eggs four weeks from now. In the meantime, carefully examine the most ma- 

 ture fields. Need for insecticide protection may be apparent in two to three weeks. 



Black cutworms are causing the most serious insect problem this week. We 

 continue to have reports from south-central Illinois and have also had calls from the 

 northern tier of counties. Control of this pest has been erratic. 



