-2- 



European corn borers . In the southern third of Illinois , the emergence of second- 

 brood moths, egg- laying, and egg-hatch are well underway. Moth emergence is just 

 beginning in the central section, and will begin within another week in the northern 

 areas. Late -developing, first-brood larvae are still present in all sections. Look 

 for moth- emergence to extend into mid- to late August in these areas. 



In a survey just completed, first-generation corn borer populations in northwestern 

 Illinois averaged 3 borers per 100 stalks of corn; in northeastern Illinois, none; 

 in western Illinois, 6 borers per 100 plants; in central Illinois, 1 per 100; in 

 eastern Illinois, none; in west- southwestern Illinois, 1 per 100; in the east- 

 southeast, 1 per 100; in the southeast, 1 per 100; and in the southwest, 2 per 100. 



When a first-generation population in an area averages 5 or more borers per 100 

 stalks, the second generation can be moderately severe. Consequently, we would ex- 

 pect the western sector along the Mississippi River from Dubuque to St. Louis to 

 encounter the highest concentration of second- generation European corn borers. 



Following are comparisons of the first- generation corn borer populations for 1971 

 and 1972: 



Borers/100 plants 

 Area of Illinois 1972 1971 



Northwest 3 5 



Northeast 2 



East 



Central 1 2 



West 6 13 



Southwest 1 3 



Southeast 1 



Corn leaf aphids . A heavy concentration of these pests was reported to be damaging 

 late-maturing corn in southeastern Illinois this week. In situations like this, 

 chemical control is justified when 50 percent or more of the plants are infested 

 and when the corn is between the late-whorl and early tassel stage. For control, 

 use sprays of malathion or diazinon; but wait until tassel emergence is virtually 

 complete to ensure adequate coverage and good control. 



In central Illinois, heavy rains were apparently instrumental in reducing some heavy 

 aphid populations. The aphids had continued to remain on the tassels and upper leaves 

 in some fields, even after pollination was complete and the silks had turned brown. 

 Aphid colonies may still remain in these fields, but generally on the lower leaves 

 and lower stalks where they should not present any problems. 



SOYBEAN INSECTS 



Green cloverworms . They can now be found in soybean fields. So far populations are 

 low in the fields examined. Sizes ranged from very small (1/4 inch) to about an inch 

 in length. This green worm with white stripes will spring when it is disturbed. Six 

 or more worms per linear foot of row are enough to decrease yields if feeding occurs 

 during early pod fill. They rarely feed on the pods. To assess the populations 

 level, shake plants over the center of the rows and count the worms on the ground. 



