COLLEGE OF 

 AGRICULTURE 

 UNIVERSITY OF 

 ILLINOIS AT 

 U R B AN A-CH AM P Al G N 

 AND NATURAL 

 HISTORY SURVEY 

 URBANA. ILLINOIS 



NSECT WEED & PLANT DISEASE SURVEY BULLETIN 



HATE/COUNTY/LOCAL GROUPS/U.S. DEPARTMENT OF AGRICULTURE COOPERATING ^j Qf ' 



?0R IMMEDIATE RELEASE *%\^ eU** f 5 ' May 1 ' 197 ° 



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

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

 ■Abbreviated control measures. Each individual should check his own fields to determine 

 local conditions. 



INSECTS 



FORAGE 



Alfalfa weevil larvae are common in southern Illinois alfalfa fields, and feeding 

 damage was quite evident this week. In south-central Illinois, the larvae were nu- 

 merous and feeding was noticeable. In central Illinois (particularly in the west), 

 larvae could be found easily only on south and west slopes, where feeding was evi- 

 dent. However, alfalfa is growing rapidly and may outgrow the damage, except in 

 fields where weevil populations are high. 



Equally important is the presence of a number of wasp parasites , especially in south 

 and south-central Illinois. We cannot now establish the effect these parasites may 

 have. They are emerging early, and will attack the weevil larvae now present and may 

 eliminate them. If this is the peak of the parasitic wasp emergence, late-hatching 

 larvae will escape and we will then see a flare-up of damage; but if this is just the 

 beginning of parasitic wasp emergence, the alfalfa weevil will be in for a rough time. 



Do not apply insecticides unless they are needed. Examine each field regularly. When 

 there is feeding on 25 percent or more of the terminals and the field is more than two 

 weeks from harvest, an insecticide application may be justified. 



The insecticide recommendations are: 



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

 methyl (Guthion) . Use azinphosmethyl only once per cutting. Do not harvest for 



15 days after treatment with methyl parathion, or 16 days for azinphosmethyl. Wear 

 protective clothing. 



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



(2) a mixture of 5/4 pound of malathion and 5/4 pound of methoxychlor per acre, 



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

 per acre, or (4) 1-1/4 pounds of malathion per acre on days when air temperatures 

 will be above 60° F. for several hours after application. Do not harvest for 7 

 days after treatment with Imidan, methoxychlor, diazinon, or mixtures of them. There 

 is no waiting period for malathion. Do not apply Imidan more than once per cutting. 



