tate 



INSECT 



SURVEY 



BULLETIN 



^« T %//> 





College of Agriculture 



University of Illinois 



and Natural History Survey, Urbana, Illinois 



S. Department of Agriculture Cooperating 



/\PR -9 1968 April 5, 1968 

 INSECT SURVEY BULLETIN NO. 4 



FOR IMMEDIATE RELEASE 



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

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

 individual should check his own fields to determine local conditions. Before ap- 

 plying insecticides , read the labels carefully and follow all precautions. This 

 will not only insure personal safety, but will also prevent residue hazards. 



Alfalfa weevils continue a slow buildup in southern Illinois. Egg hatch and larval 

 feeding have been reduced by the cool weather. Thus, the expected damage has not 

 yet occurred. However, some fields south of Route 13 have terminal feeding damage 

 of about 10 percent, but treatment should be delayed in these fields until 25 per- 

 cent or more of the terminals are damaged. Depending on the weather, the first 

 insecticide applications may be necessary south of Route 13 in the second week of 

 April, and 10 days to 2 weeks later north of this line. [In cool weather (below 

 40° F.), larvae do little or no feeding.] 



It is most important to inspect alfalfa fields frequently. Spraying too early or 

 too late can be a waste of time and money. A spot check of alfalfa tips will give 

 you some indication of damage. Select 25 terminal tips at random in several loca- 

 tions of the field, and carefully examine them for the presence of small larvae or 

 feeding injury. Apply the insecticide when larval feeding has become apparent on 

 25 percent or more of the terminals. Newly-hatched larvae are about 1/20 of an 

 inch long and are yellow, except for a shiny black head. When full grown, they 

 are about 3/8 of an inch long, green, with a wide white stripe down the middle of 

 the back. 



The recommendations are: 



1. Experienced commercial applicators who have the proper protective clothing will 

 get best results with methyl parathion applied at 1/2 pound per acre or a spe- 

 cial alfalfa weevil spray of azinphosmethyl (Guthion) at 1/2 pound per acre. 

 Azinphosmethyl can be applied only once per cutting. 



2. The person not properly equipped with protective clothing to use methyl para - 

 thion or azinphosmethyl can use a mixture of 3/4 pound of malathion and 5/4 

 pound of methoxychlor per acre, or a mixture of 1/2 pound of diazinon and 



1 pound of methoxychlor per acre (3 quarts of the commercially prepared mix- 

 ture, Alfatox) . When air temperatures are above 60° F., you may also use 

 1 1/4 pounds of malathion per acre. 



