needed to determine its most effective use on cropland without risk of injury 

 to susceptible crops grown in rotation w^ith corn. 



Simazine has a low oral toxicity (LDgo^BOOO mg./kg.) for mice. 



Atrazine is more water soluble and less persistent in soils than simazine. 

 Atrazine has been effective as a pre -planting soil-incorporated treatnnent for 

 control of quackgrass and many annual broadleaved weeds and weed grasses 

 in field corn. Pre-emergence treatments have also been effective in control- 

 ling many annual weeds in corn. 



3,5-DIMETHYLTETRAHYDRO-l,3-5,2H- 

 THIADIAZINE-2-THIONE [DMTT] 



DMTT is a volatile soil sterilant that can be applied without the use of an 

 airtight cover over the soil for control of w^eeds, soil fungi, and nematodes. 

 It nnay be applied as a dry powder or as a spray (wettable po'wder). After 

 application in either form, the material is mixed into the soil to a depth of 

 about 6 inches. This treatment is most effective when followed by at least 1 

 inch of irrigation, A 21 -day interval should elapse between time of treatment 

 and planting crops. 



3-AMINO-l, 2, 4-TRIAZOL,E [amitrole] 



This herbicide is generally available as a water soluble white, crystalline 

 powder. It has shown promise for control of Canada thistle, leafy spurge, 

 Russian knapweed, quackgrass, Bermudagrass, sedges, horsetail rush, 

 cattails, and tules, and several woody plants such as poison ivy, poison oak, 

 white ash, and prickly ash. Amitrole is translocated throughout the plant and 

 affects the grow^ing points, producing chlorosis and inhibition. It is quickly 

 inactivated in most soils. 



A nnixture of amitrole with amnnonium thiocyanate in equal parts 

 [amitrole-T] has proved more effective than amitrole alone on sonae species, 

 particularly water hyacinth and water lettuce. 



Amitrole is low in oral toxicity (L1D50 = 15,000 mg./kg.) for mice. 



N-1-NAPHTHYLPHTHALAMIC ACID [NPA] 



This chemical may be formulated as the sodium salt, imides, and acids. 

 The sodiunn salt of NPA is available as a wettable powder and as a liquid 

 concentrate. Presently, NPA sodium salt is being used for pre-emergence 

 control of grasses and broadleaved w^eeds in cucumbers, squash, cantaloupes, 

 and other crops in the cucurbit group. It also has shown some promise for 

 weed control in irrigated cotton in the West, NPA has low oral toxicity 

 (LD 50 := 8,200 mg./kg.) for rats. 



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