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FOR IMMEDIATE REIEASE August 12, i960 



HJ5ECT SURVEY BULLETIN NO. 17 



This is the seventeenth in a series of weekly bulletins on the general in- 

 sect situation in Illinois (fruit insects excepted), prepared "by entomologists of 

 the Illinois Natural History Survey, University of Illinois College of Agriculture 

 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. 



Face flies ; Populations continue to increase. Some farmers are report- 

 ing as many as 80 flies per head, and it is very likely that populations will be- 

 come greater during the next month. 



DDVP, 0.2$, in a mixture of 75$ corn sirup and 2.% water has been ap- 

 proved as a bait. Apply daily to the foreheads of cattle with a single six-inch 

 stroke of a small paint brush. Morning applications are recommended daily for a 

 two-week period, followed by other applications as needed. When face flies feed 

 on the bait, the population is soon reduced to non-economic levels. It is hoped 

 that products conforming to this label will soon be on the market. In the mean- 

 time, standard livestock repellent sprays for dairy cattle will give a few hours 1 

 relief from the flies. Backrubbers that enable the animals to rub their heads on 

 them can be used with % DDT or toxaphene for beef cattle. Allow 30 days to elapse 

 between this treatment and slaughter. 



European corn borer ; With the cool weather of the past few days, it is 

 entirely possible that pupation of the first generation has stopped in northern 

 Illinois and will not continue. This means that the second-generation population 

 in the northern area may not be so large as anticipated. Although egg masses can 

 be found, no concentrated heavy egg-laying has been observed as yet. 



Sweet corn canners should, however, continue to carefully check fields 

 that are 10 or more days from harvest and apply control measures as necessary. 

 Along with corn borer, corn earworm may well become a serious problem on later 

 planted sweet corn. 



Fall armyworm ; Some late fields of corn have spotted infestations of 

 this pest. The leaf feeding of the small worms is now noticeable as they eat small 

 areas in the leaves and only the white leaf tissue remains. The worms are found 

 deep in the whorl. They usually attack late -planted fields. DDT or toxaphene can 

 be applied, provided the corn is not to be used for ensilage or stover. 



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

 insect has on yield. 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 specific recommendations 

 on when or when not to treat. We have had reports that 10 to 20 percent of the 

 plants in a few fields are covered with aphids. If aphid control is to be attempted 

 in infestations of this size, leave an untreated section in the field for yield 

 comparison. 



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