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



readily eat the weed, are control methods commonly practiced. 

 Chemical sprays are fairly effective, but can not be used in meadows 

 where clover is grown, as clovers are killed by the solution. Sprays 

 have been found most effective while the plant is in bloom. 



The stickweed or aster (Aster ericoides), known also as frost- 

 weed, steelweed, white heath, etc., and related species, are com- 

 mon and abundant weeds in old fields in tobacco-growing sections 

 of the Atlantic States. They are perennial and thrive on poor soil. 

 It is useless to try to eradicate them completely, but they can be 

 readily controlled by growing cultivated crops and by putting the 

 land in a higher state of fertility by the use of lime and clover. 

 Aster is not a usual food plant of the tobacco Crambus, but as the 

 weed is so frequently associated with daisy and plantain, which 

 thrive best under similar soil conditions, its control is essential in 

 the preparation of land for tobacco. 



CROP ROTATION. 



One of the main reasons for a rotation of crops is that the accumu- 

 lation of weeds in meadowland and pastures may be destroyed 

 during the cultivation of the crop that follows. A rotation found 

 very satisfactory by the Virginia experiment station has been 

 devised by Mr. E. H. Mathewson, Crop Technologist of the Bureau 

 of Plant Industry. This plan is slightly modified to meet condi- 

 tions in different tobacco-growing sections. It calls for a seven- 

 year rotation of crops, as follows: First year, tobacco, fertilized 

 heavily; second year, wheat without fertilizing; third and fourth 

 years, mixed grasses and clover, seeded alone early in the fall and 

 top dressed early in the spring with 200 to 300 pounds of nitrate of 

 soda; fifth year, corn, with barnyard manure and a small amount of 

 fertilizer; sixth year, cowpeas, fertilized with a little acid phosphate 

 and sulphate of potash; seventh year, tobacco. 



Crops such as cowpeas, soy beans, and crimson clover, which aid so 

 greatly in fitting land for increased and more profitable yields of 

 tobacco and corn, not only add humus to the soil and increase the 

 fertility, but help to eradicate certain weeds by smothering them out. 

 The weeds are also destroyed or prevented from maturing seed when 

 crops are plowed under. Although eggs of the Crambus may have 

 been deposited in such a field, the larvge can not survive until the 

 tobacco is planted unless there are weeds which remain alive over 

 winter to supply them with food. 



The following rotation experiments have been under observation 

 during the present investigation : 



A test with tobacco following crimson clover was conducted as a 

 cooperative experiment on the J. R. Horsley farm in Appomattox 

 County, Va., in the season of 1910-11. The field selected contained 



