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FOR IMMEDIATE RELEASE August 2, 1°63 



INSECT SURVEY BULLETIN NO. 16 



This is the sixteenth 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 meas- 

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

 his own fields to determine local conditions. 



Corn borer egg masses for a second generation are now being deposited 

 in numbers. Over 90 percent of the first- generation borers have pupated in east, 

 central, and northwestern Illinois; 25 to 75 percent of the moths have already 

 emerged. In northeastern Illinois, pupation and emergence are somewhat later. 

 In all areas except northeastern Illinois, egg-laying should reach its peak next 

 week if nights are warm and calm, but some eggs will continue to be laid through 

 mid- to late August. 



The moths will remain in the fields from which they emerged and will 

 deposit eggs in these fields for a short time. Then they will migrate to late- 

 developing corn, where they will concentrate their egg-laying. 



Sweet corn canners should already have started a control program in late 

 fields of corn, particularly those to be harvested after August 15 . 



In field corn it is difficult to determine which fields will have enough 

 infestation to profit from control. If there are 100 or more egg masses per 100 

 plants, treatment could be profitable. But do not treat corn that is to be used 

 for ensilage. One pound of DDT per acre in the form of granules or 1 l/2 pounds 

 as a ground spray should provide adequate control en corn to be harvested only as 

 grain. 



One factor that may greatly affect egg-laying is a protozoan parasite 

 that first appeared in Illinois in the early 1950s. In some fields we have found 

 as high as 7° percent of the pupating first- generation borers infected by this 

 parasite. Infected moths are often incapable of laying eggs or may lay infertile 

 eggs. Fertile eggs from infected moths often produce borers that live only a short 

 time. We are unable to assess the overall effect this disease may have on numbers 

 of second- generation borers. 



Grasshoppers are still abundant in many hay fields in Illinois. The 

 highest numbers of grasshoppers and the highest percentage of infested fields are 

 in northwestern Illinois. Damage is apparent in some hay fields now. These grass- 

 hoppers will migrate when the hay is cut. 



To avoid killing pollinating insects if alfalfa or clovers are in bloom, 

 apply insecticides only in the late afternoon or early evening. If your sprayer 

 has been used for 2,4-D, clean it out thoroughly before spraying legume or soybeans. 



For pasture or hay crops, apply 3/^ pound of sevin, 1 pound of malathion 

 or 3/4 pound of dibrom per acre. Sevin does not require any waiting period between 

 application and grazing or cutting for hay, but allow a 7-<lay interval with mala- 

 thion and a 4-day interval with dibrom. Diazinon may be used only on alfalfa, 



