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FOR IMMEDIATE RELEASE August 19, I960 



INSECT SURVEY BULLETIN NO. 18 



This is the eighteenth and last in a series of weekly bulletins on the 

 insect situation in Illinois (fruit insects excepted), prepared by entomologists 

 of the Illinois Natural History Survey, University of Illinois College of Agricul- 

 ture, and cooperating agencies. These reports are generalized, and each individual 

 should check his own field to determine local conditions. 



Face flies . This insect continues to be serious on cattle and horses in 

 the northern half of Illinois (north of Highway 36). Herds this past week averaged 

 kO face flies per animal in this area, and one herd averaged as many as 130 per 

 head. In this same herd a single animal carried over 300 flies. 



Runny eyes and eye diseases are common among cattle bothered by these 

 flies. In addition, infested animals stop grazing, bunch up, twitch their ears 

 and shake and rub their heads. The energy cattle spend in fighting face flies, 

 coupled with shortening of the grazing period, lowers milk and beef production. 

 The situation is not expected to improve until after the first frost, when flies 

 will begin to hibernate. 



To estimate the severity of face flies on a herd, make counts between 

 10 a.m. and k- p.m. on a sunny day. 



DDVP, 0.2$, in a mixture of 75$ corn syrup and 25$ water has been approved 

 by the USDA and FDA as a bait for face flies. Apply daily with a single six-inch 

 stroke of a small paint brush to the foreheads of cattle. Morning applications of 

 the bait are recommended daily for a two-week period, followed by other applica- 

 tions as needed. It is hoped that products conforming to this label will soon be 

 on the market. Repellent sprays used against biting flies on dairy cattle will 

 give a few hours 8 relief from face flies. Lasting sprays of Diazinon or ronnel 

 used inside the barn on ceilings and walls against house flies may also help to 

 reduce face flies that enter buildings and sheds on cool, cloudy days. Backrubbers 

 that enable the animals to rub their heads on it and smear on a liberal amount of 

 insecticide can be used with 5$ DDT or toxaphene for beef cattle. Allow 30 days 

 to elapse between this treatment and slaughter. 



European corn borer . Development of this insect is slow because of the 

 recent cool weather. In the northern area (north of Highway 6), less than 50$ of 

 the first-generation worms have pupated to form second-generation moths; 85-90$ 

 of the worms that pupated have emerged as moths. Egg-laying in the late-maturing 

 fields (pretassel to fresh silk) remains low. Counts averaged 20 egg masses per 100 

 plants in these fields in the northern section. Between 30 and hC$ of the eggs 

 were hatched, but egg-laying should continue for the next two to three weeks in 

 this area. The large number of late-maturing fields available to the moths for 

 egg-laying will help to reduce numbers in any one field. However, late-maturing 

 fields will still profit from treatment for the next two weeks in this area, pro- 

 vided there is an average of 100 or more egg masses per 100 plants. Optimum time 

 for treatment is past in most of the area south of Highway 6. 



Corn leaf aphids . There is little information on the actual effect this 

 insect has on yield, and as a consequence positive statements regarding benefits 

 of control can not be made. It is known that heavy infestations of the insect are 

 related to barrenness and decrease in ear size, but no actual figures on percent 

 of plants infested and effect on yield are available to make specif ic^ recommenda- 

 tions as to when and when not to treat. Timing of treatments may also be as' 



