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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 



ATE/COUIMTY/LOCAL GROUPS/U.S. DEPARTMENT OF AGRICULTURE COOPERATING 





FOR IMMEDIATE RELEASE 



No. 20, August 3, 1973 



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 



SOYBEAN INSECTS 



Green cloverworms are present in many fields of soybeans in the northern one -half to 

 two-thirds of Illinois. Some fields are being damaged and need treatment, but the po- 

 tential for more widespread damage exists. Many small worms (green and threadlike 

 and 1/8 to 1/4 inch long) can be found and many more may yet hatch. Several fields 

 averaging 5 to 7 of these small worms per foot of row were observed this week in the 

 north-central section. However, some of the large worms were found infested with a 

 fungus disease. This disease kills the worms, and they appear white, dry, and hard. 

 Wet, humid weather is conducive to the spread of this disease. A few parasitized 

 worms with a small white egg glued behind the head were seen also. Diseases and 

 parasites are often high when populations of green cloverworms are high, and this 

 may alleviate the situation. 



Continue to check your soybean fields that are between bloom and full-pod develop- 

 ment, and if you find 4 or more worms (half -grown worms or larger) per foot of row, 

 treatment is justified. An alternate method is to apply an insecticide when 20 per- 

 cent or more of the foliage has been eaten and the worms are still present. 



For control, apply carbaryl (Sevin) or malathion at 1 pound per acre as sprays over 

 the foliage. 



CORN INSECTS 



Second-generation European corn borer moth egg -laying is well along in the southern 

 section of Illinois, is under way in the central section, and is just beginning in the 

 northern section. Our first-generation corn borer survey showed populations to be 

 generally low throughout the state. There are localized areas like bottomlands in 

 western Illinois with relatively high populations, so second-generation corn borers 

 could still be a problem in some areas . A third generation of corn borers could also 

 present problems in the southern section later on. 



The moths prefer to deposit their eggs on corn in the late-whorl to early-silk stage. 

 Egg- laying will continue for 2 to 3 weeks. 



Check late -maturing fields this week in the southern and central sections and next 

 week (August 5) in the northern sections to determine whether treatments are needed. 

 If there is an average of one or more egg masses per plant, apply an insecticide after 



