WEEDS 



Is It Too Late To Spray Corn With 2,4-D? 



Most 2,4-D labels say not to spray corn from the tasseling to the dough stage. 

 Whether or not the corn is subject to much injury at that stage is somewhat con- 

 troversial. Based on field studies and observations, it is difficult to establish 

 that 2,4-D has much of a direct effect on silks that would interfere with fertil- 

 ization. And, under field conditions, it is rather difficult to study the effect 

 of 2,4-D on pollen viability. Conceivably, 2,4-D that has translocated in the 

 plant might affect silking and tasseling, even though it was not directly applied 

 to the silks and tassels. 



Mid-season hybrids silk about 60 to 70 days after corn emergence- -depending on 

 the hybrid, the season, and the date of planting. If plenty of pollen is avail- 

 able, the silks are pollinated soon after they emerge from the husks. But where 

 stands are uneven, the time for pollen shed and silk emergence can be extended. 



About two weeks after the silks emerge they will be dry. The plant reaches the 

 dough stage about 3 to 4 weeks after the silks emerge. 



To be on the safe side, it is best to follow the indicated label precautions and 

 not spray from the tasseling to the dough stage . This is a crucial stage in the 

 development of the corn plant. 



In addition, large weeds are competing with the crop by late July and August. 

 They may have already formed viable seed, and they are not easily controlled. 

 Dense shade in high -population fields can considerably depress the growth of 

 many weeds. 



While you may have more time to spray 2,4-D now, your control would have been 

 much better in most fields if you had used 2,4-D earlier. Also, there is still 

 some risk of 2,4-D making corn brittle and causing injury. 



A "Color Chart for Estimating Organic Matter in Mineral Soils in Illinois" (AG 1941) 

 is available from the Office of Publications, College of Agriculture, University 

 of Illinois, Urbana, Illinois 61801. 



The chart, prepared by John Alexander of the Agronomy Department, can help you 

 estimate the organic -matter content of soils on the basis of color. The guide 

 should also be of considerable help to you in determining the appropriate herbi- 

 cide rates for adequate weed control, as well as minimum cost and residue. 



NOT FOR PUBLICATION 



Special Note to County Extension Advisers, South-Central and Southern 



Two field meetings especially for county Extension advisers will be held on the 

 identification, damage, and control of the European corn borer. We invite you to 

 attend. 



Tuesday, July 30 Bond County Extension Adviser's Office, 1:00 p.m. 



Wednesday, July 31. . .Richland County Extension Adviser's Office, 1:00 p.m. 



