-J- 



plants with leaves extended; split the stalk open and measure from the tip of the 

 developing tassel to the base of the plant; divide the tassel height by the plant 

 height; and multiply by 100. That figure is the tassel ratio. If the tassel ratio 

 is at least 55 (preferably 40 to 45) and at least 75 percent of the plants show whorl 

 feeding, treatment is justified. 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 granules, not sprays or dusts. Allow JO days 

 between treatment and the ensiling of corn when applying diazinon; carbaryl has no 

 waiting period. Commercial applicators may prefer to use parathion, which provides 

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

 ment and harvest. 



Corn flea beetles are appearing, but their number remains low except in an occasional 

 field. They can damage stands when the population is high. Both the black beetles 

 have been observed on small corn. If damage to newly emerging corn is severe and 

 plants are being killed, apply 5/4 pound of carbaryl (Sevin) --preferred on dairy farms - 

 or 1-1/2 pounds of toxaphene per acre as a band spray over the row. They inflict 

 white scratch marks on the first 5 or 4 true leaves and may cause the seedling to ap- 

 pear whitish or silvery. Do not contaminate fish-bearing waters when using toxaphene. 



Black cutworm problems have been few thus far. Although damage is more likely to 

 occur in low, wet spots, these cutworms may attack on hillsides too. Check the low 

 spots in cornfields regularly; watch for missing, cut, or wilting plants. The small, 

 gray-to-black worm can usually be found in the soil near the damaged plant. Corn 

 plants cut above the growing point or heart will recover. 



If damage appears, use a spray directed at the base of the plants of carbaryl (Sevin) 

 at 2 or 5 pounds, diazinon at 2 pounds, toxaphene at 5 pounds, or trichlorfon (Dylox) 

 at 1 pound of actual chemical per acre. It is best to use at least 20 gallons of 

 water per acre; also, to cover the spray band by throwing soil at the base of the 

 plants with a cultivator. 



If you know the location of a black cutworm problem field, please contact us . 



Thrips can be found in the whorl of all corn plants in southern Illinois. Their 

 feeding appears as tiny streaks of white mottling on the leaves. When thrips are 

 abundant, the damage may give the field a wilted, silvery appearance. Do not con- 

 fuse thrip damage with the silvery colored upper corn leaf damage caused by wind or 

 cold. Insecticides are seldom needed to control thrips on corn. There arc two 

 species; the adult of one species is yellow and white, the other is black. Fully 

 grown adults are about 1/16 of an inch long. 



Corn blotch leaf miners are appearing in cornfields around the southern areas. The 

 adult lays eggs in the surface of the corn leaf. The larvae leave mines, or trans- 

 parent galleries. The feeding and egg-laying punctures made by the adult (a gray- 

 to-brown fly) probably have little effect on plant vitality. Likewise, the leaf 

 mining by the larvae seldom causes injur)'. 



SMALL GRAIN 



True armyworm populations continue to remain low in most thick, rank stands of small 

 grains (wheat , barley, rye, grasses) throughout the southern half o\~ the state. It 

 is advisable to make spot checks in small grain fields for another two weeks. Cool, 

 wet weather is favorable for the development of nrmyworms. 



