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few eggs are still being deposited in the area north of St. Louis, south of Rock 

 Island, and west of Route 51. The borers are entering the stalks, and the time for 

 best results from applying an insecticide is almost over. In northern and eastern 

 Illinois, the time to apply an insecticide will be this coming week. The number of 

 borers is low in eastern Illinois, and only a few fields require protection. 



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. 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 car- 

 baryl (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 

 applicators may prefer to use parathion at 1/2 pound actual per acre, which will pro- 

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

 treatment and harvest. 



Black cutworms are still around, although they seem to be decreasing in number. We 

 had several calls from eastern Illinois this week. Again, we say that in fields of 

 corn in the rotary-hoe stage, cutworms cut plants above the growing point or heart. 

 About 60 to 80 percent of these plants will grow into healthy stalks. So, do not 

 disk-up such fields. The taller corn plants may be killed, since the worms cut off 

 the plant below the heart. 



Control varies. We have had reports of failures from practically all planter-time 

 treatments, including aldrin and heptachlor. In fact, we have had several complaints 

 about failures of these materials even when they were broadcast. Sprays of toxaphene 

 and carbaryl (Sevin) have given varying results. In some instances, control has been 

 almost perfect ; in others , control was only moderate . We hope to have methods next 

 year that will provide more -cons is tent control. 



Corn blotch leaf miners tunnel into corn leaves and make a narrow streak up and down 

 the leaf between the upper and lower surfaces. You will usually find a dirty-yellow 

 to green maggot in the tunnel. No damage is done, and this is usually more of a 

 curiosity than anything else. 



Leafhoppers are laying eggs in the tissue of corn leaves. The egg mass is usually 

 fan -shaped, and each egg represents a fan rib. They will not scrape off, as corn- 

 borer egg masses do. Leafhoppers are not important. 



Lady beetle adults are present in corn fields, laying their orange eggs. These 

 elliptical-shaped eggs are attached upright on the corn leaf, and are layed in clus- 

 ters. Lady beetles and their young eat other insects. 



Green lacewings deposit tiny white eggs individually on the stems of corn leaves. 

 The young is the aphid lion, which eats aphids and other insects. 



