COLLEGE OF 

 AGRICULTURE 

 UNIVERSITY OF 

 ILLINOIS AT 

 URBANA-CHAMPAIGN 

 AND NATURAL 

 HISTORY SURVEY 

 URBANA. ILLINOIS 



INSECT WEED & PL A NT DISEASE SURVEY BULLETIN 



S\TE/COUNTY/LOCAL GROUPS/U.S. DEPARTMENT OF AGRICULTURE COOPERATING 



FOR IMMEDIATE RELEASE 



No. 19, August 6, 1971 



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 de- 

 termine local conditions. 



THE LIBRARY OF THE 



INSECTS 



CORN 



SEP 3 1971 



UNIVERSITY OF ILLINOIS 

 AT UREANA-CHAMPAIGN, 



European corn borers . The situation is almost anybody's guess. So far very little 

 egg -laying has taken place in south-central and western Illinois, although moth emer- 

 gence is almost complete. Based on the first -generation populations, these areas are 

 !the ones most likely to have a high number of second-generation borers. Moth emer- 

 gence in northern Illinois reached 40 percent this week. Field observations lead us 

 to believe that egg- laying will be spread out over a. period of two to three weeks. 

 At any one time, egg counts may not approach the economic level of 100 egg masses 

 per 100 plants, but cumulative counts over a month may be much greater. 



It is difficult to determine when control measures are feasible for the second brood. 

 Overall, we anticipate a noticeable infestation of second -generation corn borers in 

 late corn in many areas of Illinois. Late-maturing fields should be checked for the 

 presence of the borer eggs. Generally, these will be found on the undersides of any 

 of the upper five to seven corn leaves. 



To determine whether treatment is necessary, look for egg masses or whorl feeding. If 

 the average is one or more egg masses per plant , apply an insecticide after a few eggs 

 have hatched. If the corn is in the whorl stage and if 75 percent or more of the 

 plants are showing recent whorl feeding, apply carbaryl (Sevin) or diazinon granules. 

 Aerial sprays on tasseled corn are effective; but on whorl-stage corn, aerial appli- 

 cations should be granules not sprays. Use 1-1/2 pounds of carbaryl (Sevin), 1 pound 

 1 of diazinon, or 1/2 pound of parathion per acre. Allow 10 days for diazinon and 12 

 days for parathion between application and silage removal. Parathion should be ap- 

 plied only by experienced applicators . No waiting period is required for carbaryl. 



Corn rootworm adults . They are numerous in many fields in the northern half of Il- 

 linois. The western corn rootworm was found for the first time in DeWitt County 

 this week. 



1 In most fields, treatment with insecticides will not be profitable now. But treat - 

 iment may be justified in late-maturing fields where pollination may still be affected 

 l by silk feeding. Control is suggested if there are 5 or more beetles per ear, and if 

 I not more than 50 percent of the plants have silked. Sprays of carbaryl (Sevin) , dia- 

 i zinon, or malathion at 1 pound of actual insecticide or 1/4 pound of methyl parathion 

 i per acre are effective . Methyl parathion should be applied by experienced applicators 



