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FOR IMMEDIATE RELEASE June 21, I963 



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 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 determine local conditions. 



Corn borer egg-laying declined rapidly this week. Few fresh egg masses 

 were found, and moths were also scarce. In general, only the most advanced corn 

 reached a size (tassel ratio of 20 or above) that would permit hatching borers to 

 survive. Even in these advanced fields the percent of plants showing recent whorl 

 feeding remains for the most part non-economic (below 75%) . In many fields the 

 older leaves are showing feeding, but the new whorl leaves are clean, indicating 

 that the borers have already died. There is so much corn now that is attractive 

 for egg-laying that the few eggs yet to be laid will be scattered sparsely over a 

 large number of fields. 



Examine the most noticeably advanced fields in a community this week, as 

 an occasional field may profit from treatment, particularly in the area bounded by 

 a line from Rock Island to Peoria to Quincy. To determine the need for treatment, 

 examine 50 to 100 plants for signs of fresh borer feeding on the whorl leaves. If 

 75 percent or more of the plants show recent whorl feeding, check the tassel ratio. 

 To determine the tassel ratio, measure the height of the plant with leaves extended; 

 split the plant 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. Insecticides should not be applied until the 

 tassel ratio is over 35, and the best time for treatment is between tassel ratios 

 of ^0 and k$. Use 1 pound of DDT or 1 1/2 to 2 pounds of Sevin, as granules, per 

 acre. If spraying, use 1 l/2 pounds of DDT per acre, and direct the spray onto 

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

 or dusts. The rates are in terms of pounds of actual chemical per acre. Follow 

 label precautions in harvesting and feeding treated corn. 



Grasshopper hatch is progressing in northern Illinois and will continue 

 in second-growth alfalfa and red clover. Infestations in the state are spotty, and 

 the young hoppers are still confined to hibernating areas along roadsides, ditch 

 banks, fence rows, etc. If grasshoppers are abundant in these non-crop areas, apply 

 2 ounces of dieldrin or 1 1/2 pounds of toxaphene per acre. Do not apply these 

 materials near fish-bearing waters or to pasture or forage to be used for dairy 

 cattle or livestock fattening for slaughter. For hay crops or pasture, use Sevin, 

 dibrom, diazinon or malathion. Follow label directions . 



Armyworms are rapidly reaching the full-grown worm stage, and many have 

 already pupated in the area south of U.S. Route 6. Further feeding in this area 

 is not expected to be serious. Many of the worms have been parasitized by a fly 

 that lays small white eggs on the back of the armyworm, close to the head. The 

 young fly maggot that hatches burrows into the body of the armyworm, eventually 

 killing it. As grains ripen, the few remaining but nearly mature worms will move 

 out in search of more succulent food, like corn. However, these migrations are not 

 expected to be heavy. 



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 JIM 24 1963 



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