-2- 



be high and the moths tend to concentrate their egg-laying in these fields. Check 

 exceptionally advanced fields for another two weeks in western areas of Illinois. 

 Treatments can be applied about the week of June 18 . 



In the central section, moth emergence is almost complete and some egg-laying is oc- 

 curring . 



In the northern sections, pupation is almost complete and some emergence has occurred. 



To determine the need for treatment, first check the tassel ratio. Dig up a plant and 

 measure from the bottom of the plant to the tip of the longest leaf. Split the plant 

 and find the developing tassel. Measure from the bottom of the plant to the tip of 

 the tassel. Divide the tassel height by the plant height and multiply by 100. This 

 will give you the tassel ratio. If the tassel ratio is 30 or over and if 75 

 percent or more of the plants have corn-borer feeding on the whorl leaves, the field 

 should be treated- -but not until the tassel ratio is at least 35, preferably 40 to 

 50. The percentage of infested plants required to justify treatment can be reduced 

 with higher tassel ratios. 



Use 1 pound of actual diazinon in granular form per acre, or 1-1/2 pounds of carbaryl 

 (Sevin) as granules. For spraying, use the same amount of actual insecticide per acre 

 and direct the spray to the upper third of the plant. Aerial applications should be 

 as granules, not sprays or dusts. Allow 10 days between treatment and the ensiling 

 of corn when applying diazinon; carbaryl has no waiting period. Commercial applica- 

 tors may prefer to use parathion at 1/2 pound actual per acre, which will provide 

 good control of the corn borer. Parathion has a 12-day waiting period between treat- 

 ment and harvest. 



Sod webworms are attacking corn planted following sod. The worms feed at or just be- I 

 low the soil surface, somewhat as a cutworm does. Frequently the cutoff corn plants 

 are dragged to a silk-lined tube found near the base of the corn plant. As the plant 

 grows, the leaves which are injured in the whorl grow out and the feeding is apparent 

 The sod webworm larva is short, rather thick-bodied, usually spotted and coarsely 

 haired, from 1/2 to 3/4 inch long. For control, apply 1 pound of actual carbaryl 

 (Sevin) per acre as a spray at the base of the plants. 



Billbug damage to young corn stands has been observed. They are snout beetles that 

 drill holes in stalks below ground level. When the leaves emerge, they have a series 

 of holes in them. The feeding of a single beetle may kill a small plant, while a 

 larger plant may continue to grow normally with only a few rows of holes across the 

 leaves. Suckering and distorted growth are other symptoms of billbug injury. 



Wireworms damaged several fields of corn this week. If replanting is necessary, use 

 diazinon at 2 pounds actual per acre, or Dasanit, Dyfonate, prophos (Mocap, Jolt), or 

 phorate (Thimet) at 1 pound actual per acre applied as a 7 -inch band ahead of the pres 

 wheel. These insecticides will control the small wireworms, but not the larger ones. 



Excessive wind, dry, loose top soil, and too shallow planting may be mistaken for in- 

 sect damage. Stunted corn plants may result from these factors or combinations 

 thereof. 



SMALL GRAIN INSECTS 



Armyworm activity and damage are rapidly subsiding in the southern one-half of Illi- 

 nois as the worms mature and various diseases and parasites take their toll. In some i 

 localities, armyworms have migrated into corn fields from wheat fields. 



