and sprouting stunnps when the crystals or concentrated solutions are used in 

 cups (ax chips) nnade around the base of a tree or stump. 



AMS has relatively low oral toxicity (LDgQ = 3,900 mg./ kg.) for rats. 



HERBICIDAL OILS 



Herbicidal oils usually are obtained in the distillation of petroleunn and coal 

 tar. Aromatic constituents usually have the greatest influence on their herbi- 

 cidal properties. Recent research, however, has shown that a number of 

 constituents of oils affect both total herbicidal activity and selectivity. Several 

 herbicidal oils are known under a variety of names such as aromatic solvent, 

 solvent naphtha, and petroleum naphtha. These oils vary widely in their her- 

 bicidal toxicity and selectivity depending on their origin and composition. 

 One specific example is a petroleum naphtha with A. P. I. gravity 49 to 50, 

 boiling range 300° to 400° F., unsaturated compounds 0.5 to 1. percent, 

 aronnatic content 22 to 24 percent, sulfur connpounds 0.25 to 0.30 percent, 

 and a maximum aniline point to 128° F., which is being used extensively as 

 a directed post-emergence spray for control of seedling annual grasses and 

 broadleaved ■weeds in cotton. 



Stoddard solvent and light aromatic oils have been used extensively as 

 selective herbicidal oils for weed control in crops of the carrot family. Non- 

 selective herbicidal oils with high aromatic contents are being used effec- 

 tively to control Johnsongrass on ditchbanks in the Southwest. Xylol-type 

 aromatic solvents also are being used to control aquatic weeds in irrigation 

 canals and ditches in the Western States. Diesel oil, fuel oil, stove oils, and 

 other oils are used as carriers for herbicides. Oil sprays usually are more 

 effective than water sprays in wetting leaf surfaces and in penetrating waxy 

 leafy surfaces. Oil- water ennulsions fortified with dinitrophenols or 

 chlorophenols are used rather extensively for control of annual weeds in 

 orchards and alfalfa, as well as weeds on ditchbanks and other noncrop 

 areas. : 



Herbicidal oils are relatively low in oral toxicity; for exaraple, Stoddard 

 solvent: LD50 = 2,000 mg./kg. for rats. 



CHLORATES 



A number of chlorates, including sodium and calcium, are used to control 

 deep-rooted perennial weeds. They also are used for tennporary and semi- 

 permanent soil sterilization to prevent growth of all types of vegetation. 

 Sodium chlorate is used most extensively. It is a white, crystalline, water- 

 soluble powder. Sodium chlorate can be applied in dry form by hand or with 

 various types of spreaders, or as a spray using high-volume spray equip- 

 ment. 



Sennipermanent soil sterilization in humid areas requires 500 to 2,400 

 pounds of sodium chlorate per acre (3 to 12 pounds per square rod). In senni- 

 arid areas, 500 to 1,000 pounds of the chemical per acre (3 to 6 pounds per 

 square rod) are required for semipernnanent soil sterilization. Sodium 

 chlorate leaves the soil unproductive for 1 to 4 years, depending on the 



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