"Crops that may safely be sprayed: all cereals, as wheat, rye, barley and corn; 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, Fig. 156-7), chickweed (Stellaria media, Fig. 142 ), and some other of the shallow rooted sumlent weeds of lawns and grasslands can be combated more effectively by the use of salt than by any other chemical. Fine, 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 gram 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 XIII, 282 (1900); Shutt, Canada Experimental Farms, Bulletin No. 28 (1897); Report for 1899, 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.