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INSECT 

 SURVEY 



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BULLETIN^ J o^«^ 



College of Agriculture. "^ r - n, n , ntn 

 University of Illinois " l % 



and Natural History Survey, Urbana, Illinois 



U. S. Department of Agriculture Cooperating 



FOR IMMEDIATE RELEASE 



May 17, 1968 



ILLINOIS INSECT. DISEASE, A ND WEED SURVEY BULLETIN NO. 10 



This series of weekly bulletins provides a general look at the insect, plant dis- 

 ease, and weed situation (fruit and commercial vegetables excepted) , along with 

 suggested, abbreviated control measures. Each individual should check his own 

 fields to determine local conditions. The plant disease report was prepared by 

 the Department of Plant Pathology , the insect report by the department of Agri- 

 cultural Entomology and the Illinois Natural History Survey, and the weed report 

 by the Departments of Agronomy and Horticulture and the Illinois Natural History 

 Survey . 



INSECTS 



Forage Insects 



The alfalfa weevil situation has not changed greatly during the past week. The 

 number of larva remains high and feeding is evident in alfalfa fields south 

 of Highway 16. North of this line, feeding is noticeable but not severe. Larvae 

 are pupating rapidly but eggs are still hatching, so populations are expected to 

 remain high for another 2 to 3 weeks. However, no further increase in the number 

 of larva is expected, rather a gradual decline should occur as pupation continues 

 and the incidence of parasitism increases. (As high as 22 percent of the larvae 

 were parasitized by a wasp in one field this week.) 



New spring adults are appearing in southern sections; they will feed for awhile 

 in alfalfa, then move to protected places near alfalfa fields and remain quiet 

 through the summer. Adult feeding damage appears as a feathering of the leaf 

 margins, in contrast to the skeletonizing injury' of the larvae. Adult feeding 

 damage may be more evident this year than usual, since peak emergence of adults 

 is likely to occur in many fields just shortly after cutting when the new growth 

 is still short. No satisfactory control is presently available for adults. 



Most alfalfa fields in the problem area have been treated at least once, some 

 twice. In untreated and as yet uncut fields, it would be best to cut the alfalfa 

 if flower buds are present, remove the hay, and spray the new growth of the second 

 crop . Cutting itself can reduce weevil numbers, since a percentage of the unhatched 

 weevil eggs are removed with the hay and many worms will be either killed or forced 

 to pupate by exposure to the sun and the removal of their food supply. If the crop 

 has already been cut but the new growth not sprayed, watch it closely for evidence 

 of weevil damage. If it does not green-up in 2 to 5 days and worms are present, 

 treat it promptly. 



On second-crop fields that have considerable growth, apply an insecticide when 



25 percent of the plant terminals show feeding. This will mainly apply to southern 



sections, where the second or possibly third spray treatment is now needed. 



