¥2* I , 



COLLEGE OF 

 AGRICULTURE 

 UNIVERSITY OF 

 ILLINOIS AT 

 URBANA-CHAMPAIGN 

 AND NATURAL 

 HISTORY SURVEY 

 URBANA, ILLINOIS 



NSECT WEED & PLANT DISEASE SURVEY BULLETIN 



TATE/COUNTY/LOCAL GROUPS/U.S. DEPARTMENT OF AGRICULTURE COOPERATING 



,(- 



^tfti&i 



Of - *** 



FOR IMMEDIATE RELEASE 



% oL5, June 29, 1973 



This series of weekly bulletins provides a general look at the znsect, weed, and plant 

 disease situation (fruit and commercial vegetables excepted) , along with suggested, 



abbreviated, control measures, 

 mine local conditions. 



Each individual should check his own fields to deter- 



INSECTS 



CORN INSECTS 



European corn borer populations are generally light in Illinois except for an occa- 

 sional early planted field in the western area. The combined factors of a low over- 

 wintering population, delayed com planting, and heavy rains have all but eliminated 

 the threat of first-brood corn borer this year. 



We suspect that many corn borer moths were killed by the rains before they deposited 

 their eggs. Or, they may have laid their eggs and the small larvae may have died 

 before the corn crop was mature enough for them to survive. 



However, there is always the "occasional" field that bears watching. As insurance, 

 continue to check the tallest corn or fields that were planted early for signs of 

 fresh whorl feeding, particularly in the western region. If infestations are se- 

 vere enough to warrant control, treatments should be applied now. 



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

 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 car- 

 baryl (Sevin) as granules. For spraying, use the same amount of actual insecti- 

 cide per acre. Direct the spray to the upper third of the plant. Aerial appli- 

 cations should be as granules, not as sprays or dusts. Allow ten days between^ 

 treatment and the ensiling of corn when applying diazinon. Carbaryl has no wait- 

 ing period. 



SPECIAL FIELD MEETING 



Corn rootworm control with fifteen different soil insecticide treatments will be 

 evaluated on July 16 and 17 in Henderson County at the James Darrah farm, located 



