4. Rainfall 



Rainfall that occurs immediately after post-emergence foliage applica- 

 tions of herbicides may reduce the effectiveness of the amine salt formula- 

 tions of 2,4-D, water-soluble dinitro compounds, and some other foliage 

 toxicants. Usually, little harm is done if a moderate rain occurs several 

 hours after post-emergence application. The effectiveness of pre-emer- 

 gence herbicide treatments may be increased by moderate rain occurring 

 shortly after application. In low-rainfall areas sprinkler irrigation is often 

 used with good results when the water is applied immediately after pre- 

 emergence herbicides applications. If heavy rains occur soon after pre- 

 emergence treatments, however, weed kill may be reduced, or crop damage 

 increased. 



5. General Precautions on Use 



Some herbicides may cause injury to susceptible plants growing nearby. 

 Avoid spray drift of such herbicides as 2,4-D, 2,4,5-T, MCPA, silvex, and 

 others to such susceptible plants as cotton, beans, peas, and ornamentals. 

 Coarse sprays applied at moderate to low pressure are less likely to 

 drift. 



A sprayer used for herbicides should not be used for other purposes on 

 plants that are very sensitive to injury because it is difficult to remove all 

 traces of the herbicide from the sprayer. The following are examples of 

 plants that are very sensitive to 2,4-D, 2,4,5-T, MCPA, silvex, and similar 

 herbicides: cotton, tomatoes, and grapes. Such crops as alfalfa, soybeans, 

 and clovers will tolerate trace amounts of these herbicides without serious 

 injury. After thorough cleaning, the same sprayer usedfor herbicides also 

 may be used for the application of fungicides and insecticides on these less 

 sensitive crops. 



Thorough cleaning of a sprayer with warm water and a detergent should 

 remove most of the herbicide remaining in the sprayer. This cleaning 

 should be followed by filling the spray tank with a solution of 1 part house- 

 hold ammonia in 100 parts of water. Run some of the solution through the 

 sprayer boom and nozzles and allow the solution to remain in the equipment 

 for 12 to 24 hours. Remove the solution and rinse the equipment with water 

 before using. 



Activated charcoal is also useful for cleaning herbicides from spray 

 equipment. It is a much faster cleaning agent than household ammonia. 

 Usually, 2,4-D and similar herbicides can be removed by rinsing the 

 sprayer for about 2 minutes with a 0.25 percent suspension of activated 

 charcoal (1 pound activated charcoal in 8 gallons of water containing a 

 detergent) followed by a rinse of clean water. 



Neither of the above methods is always completely effective. To check 

 the sprayer for absence of herbicides, fill with water, then spray seedlings 

 of a sensitive test plant, such as bean, tomato, or a sensitive weed. If the 

 plant is not affected within 1 or 2 days, the equipment is safe for further 

 use. 



Do not store herbicides near seed, feed, fungicides, or insecticides. 



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