t^7 



COLLEGE OF 

 AGRICULTURE 

 UNIVERSITY OF 

 ILLINOIS AT 

 URBANA-CHAMPAIGN 

 AND NATURAL 

 HISTORY SURVEY 

 URBANA. ILLINOIS 



NSECX WEED & PLANT DISEASE SURVEY BULLETIN 



fATE/COUNTY/LOCAL GROUPS/U.S. DEPARTMENT OF AGRICULTURE COOPERATING 



FOR IMMEDIATE RELEASE 



Jhsu 



May 



>/§*,, 5, April 19, 1973 



This series of weekly bulletins provides a general look at the>ri,nsect, weed, and plant 

 disease situation (fruit and commercial vegetables excepted), alonti' S with suggested, 

 abbreviated, control measures. Each individual should check his own fields to deter- 

 mine local conditions. 



INSECTS 



FORAGE CROPS 



Alfalfa weevil development was slow this week. The alfalfa has been rapidly out- 

 growing the weevil feeding, but the new growth was set back by the frosts of a week 

 ago. In such fields, weevil damage may soon become apparent. The number of weevils 

 varies greatly, so examine each field carefully. Judge the need for an insecticide 

 by the number of weevils and the damage. 



In southern Illinois south of Highway Route 13 (Harrisburg to Marion to Carbondale) , 

 small larvae are very common. As many as 20 per terminal can be found. Robert Weth- 

 erell, Johnson County Extension Adviser, reports 30 to 40 larvae per sweep of an 

 insect net. Ordinarily, 20 to 30 per sweep would warrant the use of an insecticide. 

 Although most of the larvae are still small, their feeding is becoming serious in 

 some fields. By next week, damage will be quite apparent. If a field is more than 

 ten days from harvest, treatment will be justified and should be made right away. 

 Eggs are still hatching, but these larvae may be so late that they will present no 

 problem. 



In south-central Illinois north of Highway 13 and south of Highway 50 (Lawrence vi lie 

 to Salem to St. Louis) , larvae can be found readily. In that area, they average from 

 1 to 15 per sweep. Adults are still common in fields, and are depositing eggs that 

 will hatch in the next week. From 10 to 25 percent of the terminals show definite 

 feeding. Within the week of April 23, weevil damage will become more apparent and 

 the need for insecticides can be determined then. On south- sloping fields in the 

 western part of the area, weevil infestations are more advanced, so insecticides 

 can be applied profitably now. 



In the rest of Illinois north of Highway 50, populations are still low. Thus, no 

 positive statements can be made yet, except that adults were numerous as far north 

 as Effingham. 



The insecticide recommendations are: 



1. Commercial applicators. Apply 1/2 pound per acre of methyl parathion, azinphos- 

 methyl (Guthion) , or Supracide--or 1/4 pound of carbofuran (Furadan) . Use azin- 

 phosmethyl only once per cutting, and do not harvest for 16 days. Do not har- 

 vest for 15 days after a treatment with methyl parathion, 7 days after using 1/4 

 pound of carbofuran, or 10 days after using 1/2 pound of Supracide. As a general 



