24 BULLETIN 78, U. S. DEPARTMENT OF AGRICULTURE. 



on the fact that cereals and grasses are narrow-leaved plants with a 

 single seed leaf, whereas the weeds injured are broad-leaved plants 

 with two seed leaves. Spraying with a solution of iron sulphate at a 

 strength of 1 pound to one-half gallon of water was found to be fairly 

 effective on the oxeye daisy in a test made at Appomattox, Va. 

 While spraying may be practical where certain weeds in grain fields 

 are to be eradicated, it is hardly a suitable remedy under most con- 

 ditions in tobacco-growing sections, except possibly where small, 

 patches of weeds are to be destroyed. Chemical sprays have been 

 found to be more effective when applied on warm bright days when 

 the plants are dry. Immediately after weeds have been cut off close 

 to the ground an application of salt, kerosene, crude oil, or acid 

 solutions will often be found effective. In eradicating weeds from 

 pastures the salt solution is preferable, as copper-sulphate solution is 

 poisonous to stock. 



LIMING. 



Aside from improving the mechanical and chemical condition of 

 many soils, liming will be found to aid greatly in the control of several 

 of the weed pests which have been found to be the natural or favorite 

 food plants of the tobacco Crambus. Control of weed pests may be 

 accomplished by making soil conditions less favorable for the weeds, or 

 by making conditions more favorable to the cultivated crop. Many 

 weed pests, like other plants, require for their best development certain 

 soil conditions ; and they are excessively abundant in certain locali- 

 ties because soil conditions are peculiarly favorable to their growth, 

 or because conditions are less suited to more desirable plants which 

 under favorable soil conditions would crowd them out. A change in 

 the condition of the soil, brought about by the use of lime, will often 

 bring about a marked effect in checking or preventing the growth of 

 a weed pest, and at the same time make the soil better adapted to the 

 growth of certain cultivated crops such as clover. 



The sheep sorrel ' (Rumex acetosella), on which newly hatched 

 Crambus larvae- frequently feed, thrives in acid soil. Where lime had 

 been applied to certain fields, and to some of the State experiment 

 station plats in Appomattox County, Va., the sheep sorrel was 

 practically eradicated or at least checked by the better growth of the 

 clover. Plantain, daisy, and aster (stickweed), all food plants of 

 the worms, are weeds which flourish in acid or worn-out soils. In all 

 cases where data have been secured, the use of lime has resulted in a 

 marked decrease in the abundance of these weeds. Most soils in the 

 Piedmont region of the Eastern States are greatly benefited by lime, 

 and its use has in many instances resulted in markedly increased yields 

 of tobacco. In plats of alfalfa at the Appomattox experiment station 



1 Attempts to rear larvae in cages containing only sheep sorrel were not successful. 



