^j^ Cooperative Extension Service, University of 



Illinois College of Agriculture in Cooperation With 

 ^> the Illinois Natural History Survey and U.S.D.A. 



FOR IMMEDIATE RELEASE July 29, 1966 



INSECT SURVEY BULLETIN NO. 15 



This fifteenth weekly bulletin on the general insect situation in Illi- 

 nois (fruit insects excepted), prepared by entomologists of the University of Illi- 

 nois College of Agriculture, Illinois Natural History Survey and cooperating 

 agencies, reports general trends in insect activity and suggests abbreviated con- 

 trol measures. Each individual should check his own fields to determine local 

 conditions. 



Special Attention 



Dairy farmers are asking about use of drought corn for ensilage if either 

 of the soil insecticides, aldrin or heptachlor, were used at or prior to corn plant- 

 ing. Our Illinois recommendation has been for dairy farmers not to use chlorinated 

 hydrocarbons. However, these chemicals and their breakdown products are not trans- 

 located to any extent from the soil into the corn plant or ear, and little if any 

 contamination should occur if care is taken in cutting the stalk. Therefore, if 

 you use corn from treated soil for ensilage, cut the corn 12 or more inches above 

 the ground to avoid contamination from earlier splashing or excessive dust deposits. 



Our recommendation for use of 1 1/2 pounds of actual malathion per acre 

 for corn leaf aphids was in error in last week's bulletin. Label approval is for 

 1 pound as a spray or 1.6 pounds as a dust. With the severe aphid infestation, we 

 intended that the spray recommendation read 1 1/k pounds; thus 1 gallon of 5-pound 

 content malathion emulsion would do four acres. The interval between application 

 and harvest is 5 days, which applies mainly to sweet corn. If you use a. spray of 

 1 1/U pounds per acre on field corn, allow 10 days between application and harvest. 



Present Farm Insect Problems 



Corn leaf aphids are moderate to heavy in most corn in the northern one- 

 half of Illinois. The highest infestations in the state occur north of Route 36. 

 This past week they were highest from Route 36 to Route 6. This next week they 

 will spread north of Route 6. It is apparent now that infestations occurred be- 

 cause moisture was critical. The presence of aphids has been readily noticeable in 

 some fields. 



Our knowledge about the survival rate of aphids is limited. Infestations 

 usually begin when the tassel is still deep in the whorl and remain unnoticed. Num- 

 bers gradually increase for about two weeks and then suddenly "mushroom" reaching their 

 peak just after tassel emergence but prior to pollen release. In most instances 

 populations decline rapidly after pollen shed: winged aphids that migrate to later 

 planted corn or other grasses suddenly appear at this time, but the damage has 

 usually been done. However, they may persist until fall on a few plants or occa- 

 sionally on many plants in a field. We cannot explain why or when this will occur. 

 In these instances, damage will continue to worsen, some barrenness will occur, and 

 yield loss will be noticeable. 



We have 3een only a few instances of parasitized aphids. They are brown 

 and swollen. A wasp will emerge from them and lay eggs in more aphids. Some lady 

 beetle larvae and adults, aphid lions, and syrphid fly maggots are beginning to 



