effectiveness in controlling quackgrass, Bern^udagrass, Johnsongrass, and 

 other annual and perennial grasses. Best results are obtained when it is 

 applied in conabination with tillage and cultural practices. The sodium, salt 

 of TCA also is being used as a pre-enaergence spray for the control of 

 annual grasses and several broadleaved weeds in flax, sugar beets, sugar- 

 cane, and certain other crops. The residual toxicity from high rates of TCA 

 for the control of perennial grasses may disappear within a few weeks or 

 may persist for a year or longer depending on the rate of application, soil 

 type, temperature, and soil-moisture relations. The sodium salt of TCA is 

 highly soluble in water, somew^hat caustic, and may corrode spray equip- 

 ment. 



TCA has low oral toxicity (LDjg = 5,000 mg./kg.) for rats. 



2, 2-DICHLOROPROPIONIC ACID [dalapon] 



This herbicide possesses properties somewhat similar to TCA. In contrast 

 with TCA, when dalapon is applied to the foliage of grasses in the vegetative 

 stages of growth, it is translocated from the leaves to the roots of most 

 species. Dalapon has proved less erratic and more effective than TCA when 

 applied as a foliage spray for the control of most of the annual grasses. It is 

 much more effective on quackgrass, Bernnudagrass, Johnsongrass, and other 

 perennial grasses. Dalapon, commercially formulated as a sodium salt, is 

 highly soluble in water. Research indicates that it is most effective for 

 controlling perennial grasses w^hen applied in combination with tillage and 

 cultural practices. Dalapon apparently possesses less residual toxicity than 

 TCA; but further research is needed to determine the rate of disappearance 

 of the herbicide from the soil. Dalapon is effective in controlling weeds in 

 sugarcane, sugar beets, birdsfoot trefoil, alfalfa, and for spot treatment con- 

 trol of Johnsongrass and other grasses in cotton. It effectively controls 

 cattails and phragnaites on irrigation and drainage canals. 



Dalapon is low in oral toxicity (LD5q=6,590 to 8,120 mg./kg.) for rats. 



TRIAZINES 



A large number of triazines have been evaluated as herbicides and a num- 

 ber of these chemicals have sho'wn promise for control of weeds in corn, 

 cotton, grain sorghum, and as soil sterilants. The triazines are of relatively 

 low solubility in water, but are quite soluble in organic solvents. They are 

 fornnulated as wettable powders or emulsifiable concentrates. Some of those 

 for which practical uses have been developed include 2-chloro-4,6-bis 

 (ethylamino)-s-triazine [simazine] and 2-chloro-4-ethylamino-6-isopro- 

 pylamino-s-triazine [atrazine] . 



Simazine is effective as a pre-emergence treatnnent for control of many 

 annual broadleaved weeds and weed grasses in field corn. High rates of appli- 

 cation have been effective in controlling all vegetation on noncrop areas. 

 Because of the long residual action of this herbicide, further research is 



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