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Black cutworms are very severe in many fields of corn throughout central 

 and south-central Illinois. They are generally found in fields where no soil in- 

 secticides were used prior to planting, but they are also commonly found in fields 

 where insecticides were applied in the row at planting. Also, there have been nu- 

 merous reports of cutworm outbreaks in fields where the soil insecticide was broad- 

 cast and disked in prior to planting. 



The worms vary in size, but most of them are more than half grown and will 

 mature within 10 days. There is usually not another generation in the same locality, 

 but one can develop as it did in 1953, when moths of the first generation remained 

 and did not migrate northward. Continued rains with wet spots in fields in about 

 two weeks could prove attractive to the newly emerging moths for lajing eggs. 



If post-planting treatment is needed, use either 1/2 pound of actual diel- 

 drin or 3 pounds of actual toxaphene. Do not use dieldrin or toxaphene on dairy farms 

 or allow the drift to reach dairy pastures or hay crops. For dairy farms, use 2 pounds 

 of actual carbaryl per acre. It will be helpful, but not highly satisfactory. If 

 replanting is necessary, apply a broadcast application of a soil insecticide. 



In general, surface applications of dieldrin or toxaphene may vary in ef- 

 fectiveness from no control to perfect control. The results will depend upon soil 

 moisture at spraying, or on rain immediately after spraying. If it is dry, the worms 

 will be several inches deep in the ground and the spray will stay on the surface — 

 thus no kill. 



Corn borer emergence should be nearing completion in the southern tip of 

 Illinois. This week will be the time to decide whether it will pay to apply an in- 

 secticide to the earliest and most mature corn. 



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 (pref- 

 erably U0 to i+5) and at least 75 percent of the plants shew recent whorl feeding, 

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

 acre or 1 1/2 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. 



In northern, northwestern and western Illinois, pupation of overwintering 

 borers ranges from 50 to 95 percent, with an occasional moth already emerged. Borer 

 development is normal for this area, but corn development is slightly later than in 

 the past few years. Egg laying will start in the next few weeks. Be prepared to 

 examine those except ionally early fields from mid-June to July k. 



Chinch bug populations in eastern and central Illinois may have been greatly 

 affected by the rains, but the extent cannot be determined for another week. 



Alfalfa weevil has now been found in Vermilion county. 



