FOR IMMEDIATE RELEASE June 19, 1964 



INSECT SURVEY BULLETIN NO. 10 



This is the tenth 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 im- 

 pending changes in insect activity and to suggest abbreviated control measures. 

 These reports indicate only general trends. Each individual should check his 

 own fields to determine local conditions. 



Corn "borer pupation is complete and moth emergence is nearly complete 

 throughout Illinois, with the possible exception of the northernmost tier of coun- 

 ties. The overall situation is difficult to diagnose, since we have been unable 

 to assess the effect of recent rains on corn borer moth population. Also, cool, 

 rainy nights discouraged egg- laying. Warm, calm nights would speed it up. 



In general, egg counts were extremely low this week on the east side 

 of the state, slightly higher in the middle section, and highest in the west. 

 Egg- laying is nearly complete in the central and western parts of the state south 

 of Route 9, but will continue for almost two weeks north of Route 9. It appears 

 that the week of June 22 will be the critical time for decisions about treatment 

 in the area west of Route 51 between Routes 9 and 6, and the week of June 29 will 

 be critical in the area north of Route 6 and west of Route 47. It is doubtful 

 that other areas will have enough borers to warrant insecticide use. 



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 40-45) 

 and at least 75 percent of the plants show recent whorl 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. Fhorate (Thimet) and diazinon as granules also have label approval for 

 corn borer control. 



Armyworms are still found in occasional fields of grain or grass in 

 northern Illinois. Check thick stands of oats carefully for the next two weeks. 

 In central Illinois worms have all pupated and the moths are abundant and are 

 attracted to lights. Ordinarily the moths migrate northward and there is not a 

 second damaging generation in an area in one year. 



This week we have had questions about possible drift of dieldrin spray 

 onto the edges of hay crops to be fed to dairy cattle. If there is any question 

 about drift, it is safest not to use the hay from that area of the field for dairy 

 cattle or livestock fattening for slaughter. The next cutting will be all right. 



Grasshoppers are hatching, and small ones can be found in fence rows, 

 ditch banks, and similar areas. It is not time to use insecticides, since hatch 

 has just started and will continue for two weeks or more. 



•,• 



! UN 22 1964 



