spraying often slow plant growth and retard herbicidal activity. High tempera- 

 tures increase losses of herbicides that are volatile and increase the possibil- 

 ity of injury to crops fronn selective herbicides. The carbamates, dinitro 

 compounds, and high- volatile esters of 2,4-D, 2, 4,5-T, and other phenoxy 

 compounds volatilize rapidly at temperatures above 80° F. At temperatures 

 above 95° F., even the low^- volatile esters of 2,4-D and other phenoxy com- 

 pounds become significantly volatile. Generally, all herbicidal spray treat- 

 ments are avoided when the temperature is above 95° F. 



4. Rainfall 



Rainfall that occurs immediately after post-emergence foliage applications 

 of herbicides may reduce the effectiveness of the annine salt fornnulations of 

 2,4-D, w^ater- soluble dinitro connpounds, 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 -emergence herbicide 

 treatnnents 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 herbi- 

 cide 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 ajre 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 simi- 

 lar 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 sann.e sprayer used for herbicides also 

 m.ay be used for the application of fungicides and insecticides on these less 

 sensitive crops. 



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

 remove nmost of the herbicide remaining in the sprayer. This cleaning should 

 be followed by filling the spray tank with a solution of 1 part household 

 annmonia in 100 parts of w^ater. 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 amnaonia. 

 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 (1/4 

 pound activated charcoal in 10 gallons of water containing a household 

 detergent) followed by a rinse of clean water. 



Neither of the above nnethods 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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