118 



CHEMICAL WEED -KILLERS OR HERBICIDES 



the charlock, and this amount causes little or no 

 damage to the grain. This same treatment is 

 reported to be more or less effective against a 

 variety of other common grain-field weeds. The 



Fie. 170. Pacific Coast poison oak {Rhus diversiloba). 

 A trailing or climbing plant. 



■wild turnip (Brasswa campestris) and some allied 

 cruciferous weeds are less easily killed because the 

 spray does not adhere to their smooth leaves. 



Experiments by the Cornell Station gave the 

 following general conclusions: Wild mustard grow- 

 ing with cereals or peas can be destroyed with a 

 solution of copper sulfate, without injury to the 

 crop. A 3 per cent solution (about 10 pounds to 

 the barrel, or 40 gallons of water), at the rate of 

 40 to 50 gallons per acre, gjvesvery satisfactory 

 results. 



The following notes on the effect of the copper 

 sulfate solution on different plants are from obser- 

 vations and reports from various sources: 



"Plants reported killed by copper sulfate solu- 

 tions: wild mustard, wild radish, wild barley, 

 penny-grass (if young), shepherd's-purse, wild 

 buckwheat, lamb's-quarters, ragweed, sow-thistle, 

 hemp-nettle, bindweed, dock, dodder. 



"Plants reported severely Injured: curly dock, 

 black bindweed, dandelion, sow-thistle and senecio. 



"Plants reported as not injured: wild rose, pop- 

 pies, pigweed, spurge, corn-flower, field-thistles, 

 chamomile, couch-grass, bent-grass and horsetails. 



"Crops that may safely be sprayed: all cereals, 

 as wheat, rye,. barley and porn; the grasses; peas; 

 sugar-beets. 



"Crops that are killed or severely injured by 

 the copper sulfate solution: beans, potatoes, tur- 

 nips, rape." 



Lawn weeds. — Orange hawkweed (Hieracium 

 aurantiacum, Pig. 156-7), chickweed (Stellaria 

 media, Fig. 142 ), and some other of the shallow- 

 rooted succulent weeds of lawns and grasslands 

 can be combated more effectively by the use of 

 salt than by any other chemical. Pine, dry salt 

 should be applied on a bright, hot summer; day 



(late June or early July best), broadcasting it so 

 as to cover all plants uniformly, since it kills 

 chiefly by drawing water from the leaves. One to 

 four quarts of salt can be used per square rod, 

 with little or no permanent injury to the grass 

 if on a strong soil in the northeastern states. 

 Since the effect varies with local conditions, 

 advance trials should be made on a small scale. 

 Following the application, the dead weeds should 

 be raked out and a liberal application of grass seed 

 made. 



Poison ivy and similar woody-rooted pests can 

 be eradicated by cutting off the tops in hot, dry 

 weather in midsummer and pouring a saturated 

 solution of caustic soda about the roots. The 

 arsenical solutions mentioned above can be used, 

 but are generally objectionable because they render 

 the soil sterile for so long a period thereafter. 



Literature. 



For more extended discussion the reader should 

 consult : Bolley, The Destruction of Weeds in Ce- 

 real Crops by the Use of Chemicals Sprayed on the 

 Foliage, Proc. Soc. Prom. Agri. Sci. XX, 107 (1899); 

 Jones and Orton, The Orange Hawkweed or Paint- 

 brush, Vermont Experiment Station, Bulletin No. 

 56 (1897); Killing Weeds with Chemicals, Vermont 

 Experiment Station, Report XII, 182 (1899); Report 

 Xm, 282 (1900); Shutt, Canada Experimental 

 Farms, Bulletin No. 28 (1897); Report for 1899, 



Fig. 171. Poison sumac (Bhus venenata). 



page 194; Voelcker, The Destruction of Charlock, 

 Journal Royal Agricultural Society, England, 3 

 Series, X, 767 (1899). This last gives an excellent 

 summary of results in England. Stone, Cornell 

 University Experiment Station, Bulletin No. 216, 

 1904. . . , .: 



