INSECT 



SURVEY 



BULLETIN 



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College of Agriculture 



University of Illinois 



and Natural History Survey, Urbana, Illinois 



S. Department of Agriculture Cooperating 



FOR IMMEDIATE RELEASE 



April 19, 1968 



INSECT SURVEY BULLETIN NO. 6 



This series of weekly bulletins provides a general look at the pest situation 

 (fruit insects excepted) , along with suggested, abbreviated control measures. 

 Each individual should check his own fields to determine local conditions. This 

 release also contains a plant disease report supplied by the Department of Plant 

 Pathology and the Illinois Natural History Survey, as well as a weed control re- 

 port supplied by the Departments of Agronomy and Horticulture^ 



FIELD CROP PEST PROBLEMS 



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Insects 



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Alfalfa weevil development is now progressing rapidly. 



weevil situation this spring is quite different than it was last year. In the 

 winter of 1966-1967, weevil adults were depositing eggs and larvae were hatching 

 all winter long. As a consequence, weevil larvae were feeding on the alfalfa 

 plants even before they were growing. This past winter, although weevil adults 

 deposited a few eggs, they did not really begin to lay eggs until the beginning 

 of alfalfa growth. By the time the eggs began to hatch, alfalfa had been growing 

 for 2 weeks or longer. Either one of two things could happen because of this 

 late start: 



1. Egg laying, hatch, and damage may be condensed into a shorter period, with 

 feeding and damage severe for a short period, then declining rapidly. Egg 

 counts indicate that this may already be taking place. 



2. Egg laying may be prolonged over the same span of time as last year. In this 

 case, noticeable damage will occur late into the second growth. 



General statements are difficult to make because of the retarded development of 

 the alfalfa weevil. Therefore, each field must be judged individually. Ordinar- 

 ily, 3 applications of an insecticide are needed to control moderate to heavy 

 infestations. Make the first application when 25 percent of the terminals (in- 

 dividual stems, not plants) show feeding. A second application is required about 

 2 weeks later, since more hatch occurs and weevils migrate into the fields. A 

 third application is made to protect the new shoots of the second growth, after 

 the first cutting has been removed. 



This year, some of the early developing alfalfa may not require 2 insecticide 

 applications on the first crop. However, apply an insecticide when 25 percent 

 or more of the terminals show feeding. Examine the field 10 days to 2 weeks later. 

 If weevil feeding is increasing rapidly and the crop is still 10 days or even 



