THE SO-CALLED TOBACCO \\ I i:K\\ < >i; A I IN VIRGINIA. 



19 



In experiment No. 2 tobacco followed corn, in a plat used for 

 fertilizer tests. Tobacco was set June 6. The first replanting was 

 made June 14, with 5 per cent injury; the second replanting, June 

 23, with 3 per cent injury; and the third replanting, June 28, with 

 2 per cent injury. About 98 per cent of a stand was secured after 

 the third replanting. 



In experiment No. 3 tobacco was planted after a cover crop of 

 wheat, in variety test plats. The wheat was fallowed May 1 . Tobacco 

 was set June 7. The first replanting was made June 17, with 20 per 

 cent injury, and the second replanting, June 28, with 6 per cent 

 injury. About 95 per cent of a stand was secured. In these plats 

 it was estimated that about 5 per cent of the entire loss was due to 

 cutworms and to true wireworms (larvae of Elateridae). 



SUMMER PLOWING. 



The moths are local in habits and do not fly far from the weedy 

 fields, which furnish protection for them and which are suitable 

 places for them in which to deposit eggs. On emerging from plowed 

 or bare land, or from fields in which the vegetation is not suitable 

 for protection or for egg deposition, they fly to surrounding fields 

 where conditions are more favorable. The land from which emer- 

 gence took place will then be left free from worms which, if present 

 would attack the crop the following year. 



The preparation of weedy land for tobacco or corn must, therefore, 

 be commenced the season before the crop is planted. Best results have 

 been obtained by summer plowing, as the land was thus rendered 

 bare of vegetation, and conditions were not suitable for egg laying 

 when the moths emerged. By this means infestation of the land is 

 prevented in the first place. It has been found that it is difficult 

 to prevent injury, or to eradicate the worms, if they have once 

 become established. Summer treatment of land makes conditions 

 unfavorable for the moths to deposit eggs, destroys weeds which 

 furnish food for the young larvae, and kills many of the insects while 

 in the pupal stage. 



The results of an experiment made in 1910 to ascertain the effect 

 of plowing on pupae is given in Table VIII. Larvae were placed in 

 large field cages. When the greater number had pupated, one of 

 the cages was removed temporarily and the land plowed. 



Table VIII. — Effect of plowing on pupal stage of the tobacco Crambus. 



Cage No. 



Number 

 of larvae. 



Collected . 



Moths emerged. 



Num- 

 ber. 



118 



Per 

 cent. 



1 



200 

 200 



June: Second and third week. . . 

 do 



July: Third and fourth week., 

 do 



42 



2 (check) 



59 











