Calcium cyanamide has relatively low oral toxicity (LD^q - 1,400 mg./ 

 kg.) for rabbits. 



AMMONIUM SULFAMATE 



This water-soluble, white, crystalline powder is most widely used for 

 control of woody plants in areas adjacent to cotton, grapes, tomatoes, and 

 other plants that are susceptible to the phenoxy compounds. It will prevent 

 stumps from sprouting when applied to the cut surface, and will kill large 

 trees and sprouting stumps when the crystals or concentrated solutions 

 are used in cups (ax chips) made around the base of a tree or stump. 



Ammonium sulfamate has relatively low oral toxicity (LDcq = 3,900 mg./ 

 kg.) for rats. 



HERBICIDAL OILS 



Herbicidal oils usually are obtained in the distillation of petroleum and 

 coal tar. Aromatic constituents usually have the greatest influence on their 

 herbicidal 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 aro- 

 matic solvent, solvent naphtha, and petroleum naphtha. These oils vary 

 widely in their herbicidal 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 1.0 percent, aromatic content 22 to 24 percent, sulfur compounds 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,, 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 

 leaf surfaces. Oil-water emulsions fortified with dinitrophenols or chloro- 

 phenols 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 example, 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 temporary 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. 



- 8 - 



