JL^/L 



JK 



COLLEGE OF 

 AGRICULTURE 

 UNIVERSITY OF 

 ILLINOIS AT 

 URBANA-CHAMPAIGN 

 AND NATURAL 

 HISTORY SURVEY 

 URBANA, ILLINOIS 



MSECT, WEED & PLANT DISEASE SURVEY BULLETIN 



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



FOR IMMEDIATE RELEASE 



•£cj£ 





ay 



of 



No. 4% April 13, 1973 



Ul 



IL 



L 'lVr 



This series of weekly bulletins provides a general look at the insect, weed, and plant 

 disease situation (fruit and commercial vegetables excepted) , along with suggested, 

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

 mine local conditions. 



INSECTS 



FORAGE INSECTS 



Alfalfa weevil egg hatch, larval development, and crop growth were slowed by cold 

 weather this past week. An occasional field in southern Illinois had 70 percent tip 

 feeding, but the number of larvae were generally low. Most fields averaged less than 3 

 larvae per sweep of the insect net. About 20 per sweep is considered an economic in- 

 festation. 



Recent surveys show that alfalfa weevil egg numbers average 300 or more per square 

 foot in some fields in southern Illinois. Depending on weather conditions, we would 

 expect insecticide treatments to be warranted within ten days to two weeks south of 

 Route 13. An extended period of warm weather in this area could bring about a sud- 

 den hatch and a rapid buildup of larvae. 



If 50 percent of the terminals have alfalfa weevil feeding, an insecticide is justi- 

 fied. Note: As the number of larvae increase, a lower percentage of terminal feed- 

 ing will justify treatment, especially if alfalfa growth is slow. Watch all fields 

 closely from now on. As you examine alfalfa, the yellowish, newly hatched larvae 

 (about 1/20-inch long) with shiny black heads can be found feeding within the folded 

 leaves and buds of the plant terminals. Almost mature larvae are green with a white 

 stripe down the back. 



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 

 precaution, wear protective clothing. Higher dosages of carbofuran will require 

 longer waiting periods. Do not apply carbofuran more than once per season. 



2. Persons not equipped with protective clothing . Use: (1) Imidan at 1 pound per 

 acre; (2) a mixture of 3/4 pound of malathion and 3/4 pound of methoxychlor per 

 acre; (3) a mixture containing at least 1/2 pound of diazinon and 1 pound of 



