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WEEDS 



PERENNIAL WEED CONTROL 



The proper timing of 2,4-D applications can make perennial weed control easier and 

 more effective. Spraying when weeds are in the bud stage- -that is, when the buds 

 have formed but the flowers have not opened- -can improve control of some broadleaf 

 perennial weeds. At that stage, the weeds are ready to make the transition from the 

 vegetative to the reproductive stage. Food manufacture in the leaves is in high 

 gear, and food materials are being transported to the roots for storage. Spraying 

 at this time will aid movement of 2,4-D to the roots and will improve control. 



Wild sweet potato has a large storage tuber, and an application of 2,4-D at the bud 

 stage can improve control considerably. To get the job done at this stage may in- 

 volve spot treatment or the use of high -clearance equipment in corn fields. 



The same principle applies to the control of Canada thistle. There are several 

 strains of this perennial weed. Although they look similar and are all called 

 Canada thistle, the strains differ in susceptibility to herbicides. Some strains 

 are fairly sensitive to 2,4-D. Others are not. 



If 2,4-D does not provide good control of the type of Canada thistle in your fields, 

 amitrole or amitrole-T may be more effective. But be sure to use amitrole or 

 amitrole-T only at approved times and places. Do not use them as a postemergence 

 treatment in corn or soybeans. Do not graze treated areas for eight months. 



Canada thistle strains also show differences in susceptibility to amitrole and 

 amitrole-T. Banvel usually controls Canada thistle more effectively than 2,4-D, 

 but timing is more critical and care must be taken to avoid injury to nearby, de- 

 sirable plants. 



Repeated cultivation, mowing, or hoeing to cut-off the tops of perennial broadleaf 

 weeds also helps control by depleting root reserves when the plant sends up new 

 growth. 



GRASS WEEDS IN CORN 



Good cultivation where corn and weeds are still small enough is about all that can 

 be done to control grass weeds in corn now. The 1971 Weed Control Guide contains 

 suggestions for using dalapon (Dowpon) or linuron (Lorox) as directed postemergence 

 sprays, but these materials have stirred little interest in Illinois in the past. 

 Copies of the Guide are available from the Office of Agricultural Publications, 123 

 Mumford Hall, Urbana, Illinois 61801. There is no charge for single copies. 



BROADLEAF WEEDS IN CORN 



A postemergence application of 2,4-D can provide a lot of control at a low cost, 

 but there is some risk of corn injury. Avoid spraying during very hot and humid 

 weather. Check the labels and the 1971 Weed Control Guide for details, suggestions, 

 and precautions about using 2,4-D. 



SPRAYING SMALL GRAINS BEFORE HARVEST 



Small grain fields in some areas are surprisingly free of weeds, others are not. 

 Farmers with fields in the latter condition often ask about spraying before harvest. 



