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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 April 22, 1966 



INSECT SURVEY BULLETIN NO. 1 



This first weekly bulletin of 1966 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, reports general trends in insect activity and suggests abbreviated con- 

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

 ditions. 



Feeding by alfalfa weevil is already apparent in the seven southernmost 

 counties and will appear this week in many counties north to Highway 50. 



The adult alfalfa weevil is a brown to gray beetle about 1/k inch long 

 with a deep brown to almost black patch on its back. The females have been laying 

 eggs in alfalfa stems for several weeks and will continue to do so for some time. 

 The light green larvae with white stripes down their backs feed during the day. 

 They cling to the plant or hide in the terminals. Adult weevil feeding shows as a 

 feathering of the leaf margin, while the larval feeding skeletonizes the leaves. 



Old established stands of alfalfa are now beginning to show severe feed- 

 ing. In mixed stands the weevils are concentrating on the alfalfa plants, and se- 

 vere infestation may soon kill the plants. Although feeding is light in last year's 

 seedings, the adults are concentrating their egg laying in these fields and damage 

 will become more apparent later. 



We have seen several fields in southern Illinois in which 100$ of the 

 terminals showed damage and there were as many as 10 larvae per terminal. If 15% 

 of the terminals are infested, it will be profitable to apply an insecticide, as 

 damage will be serious. In states where weevils are more numerous, the recommenda- 

 tion is to treat when 30 to 50 percent of the terminals show damage, with an addi- 

 tional treatment prior to first cutting. 



Insecticides should be applied within the next week in the southernmost 

 counties. If infestations are severe, plan to make another application imm ediately 

 upon removal of the first cutting of hay. 



Parathion or azinphosmethyl (Guthion), 1/2 pound per acre, is effective, 

 but because both are toxic they should be applied only by experienced applicators. 

 Azinphosmethyl should not be applied within 21 days of harvest or more than once 

 per cutting, and parathion should not be applied within 15 days of cutting. 



If you wish to make your own applications and temperatures are above 60°, 

 use 1 pound of malathion per acre or a commercially prepared diazinon-methoxychlor 

 mixture. Use a minimum of 10 gallons of water per acre when spraying. There is no 

 waiting period between application of malathion and harvest. Allow one week to 

 elapse between application of diazinon-methoxychlor and harvest. 



For pastures, use malathion or the diazinon-methoxychlor mixture. You 

 can put animals right back on pastures sprayed with malathion, but allow one week 

 to elapse when using diazinon-methoxychlor sprays. 



