14 METHODS OF CONTROLLING TOBACCO INSECTS. 



cation should be made within three or four days after the eggs begin 

 to hatch. A thorough application of from three-fourths of a pound 

 to 1 pound to the acre should be sufficient to kill the young larvae. 

 Do not wait until the worms become half grown before making the 

 application, for in addition to being very much harder to kill than 

 the young ones, they will do considerable damage to the leaves before 

 they are killed. In dry weather a thorough application will remain 

 effective for a week or ten days, but if there is a rain the application 

 should be repeated immediately. The number of applications and 

 the dosage will be influenced by weather conditions — whether wet 

 or dry — by the numbers of young worms that appear, and by the 

 earliness or lateness of the crop. By watching the effect of an applica- 

 tion it can be easily determined whether it is losing its effectiveness 

 and whether another application is necessary. The presence of a few 

 large worms does not necessarily mean that the poison is ineffective. 

 Some worms will escape the most careful applications, and these 

 should be hand picked. The strength of the later applications upon 

 tobacco that is nearly grown may be increased to 1,.1£, or even 2 

 pounds to the acre. 



Caution. — Do not apply Paris green until two or three days have 

 elapsed after suckering, for if a light rain should wash the Paris 

 green into the fresh wounds made by breaking out the sucker, the 

 caustic cll'ect of the free arsenic may cause the leaves to drop oil'; 

 also, do not apply a heavy dose of Paris green to tobacco when it is 

 beginning to "grain," for the leaves are then more susceptible to 

 "Paris green burn" than they are a few days previous to "graining." 



Spraying tobacco versus dusting. — In this circular we have recom- 

 mended dusting tobacco instead of spraying for two reasons: First, 

 the labor of spraying is very much greater than that required to 

 apply the dust. When tobacco is nearly full grown, that is, has 

 begun to lap in the row, it will require from 120 to 150 gallons of 

 water to spray an acre. Therefore, to apply the spray to 1 acre a 

 5-gallon knapsack sprayer must be refilled from 24 to ,30 times. 

 Second, the Paris green is not kept in suspension very easily in a 

 knapsack sprayer and the last of the spray from the tank is likely to 

 contain more than its proportion of the Paris green and thus cause 

 injury to the plant. Furthermore, if great care is not used in apply- 

 ing the spray, a part of the plant is very likely to be drenched and 

 the Paris green will be collected along the midribs and in the axils 

 of the leaves in sufficient quantity to cause serious injury. It is not 

 denied that a more even and thorough application can be made in 

 spray form, but with negro labor, and with most white labor, we do 

 not believe it will be made as satisfactorily as in the dust form. 



Arsenic left upon tobacco. — There is fear among growers that if 

 arsenicals are used a sufficient amount of arsenic may be left 



