Pebruary/22] headlee: contact dusts 77 



The above table senses to show that a 2% nicotine clay calcium 

 oxide dust kills 87% of the plant lice, while under the same conditions 

 nicotine delivered as a spray kills very slightly over 85%. It also 

 shows that a 1% nicotine clay calcium oxide dust kills nearly 84%. 

 This table shows that nicotine dust kill reaches its maximum between 

 24 and 72 hours after application, while nicotine delivered as a spray 

 reaches a high point of kill within the first 24 hours after application 

 and that the vast bulk of its kill is accomplished within the first 2 hours. 

 If rain falling within the period covered by the kill of the dust should 

 promptly put an end to the nicotine dust activity this long period of 

 kill would be a decided disadvantage to the employment of nicotine 

 dusts. As a matter of fact a 1.88% nicotine clay, calcium oxide dust 

 destroyed about 87% of the aphis within an exposure of 48 hours, and a 

 3.64% nicotine clay calcium oxide dust destroyed 66.6% of the aphis 

 after an exposure of 8 hours at which time a heavy rain fell. When we 

 take into consideration the fact that with a percentum of nicotine 1.76% 

 larger the kill is 20.4% less when rain interfered, we are compelled to 

 ■conclude that rain coming within the period of kill constitutes a very 

 serious interference with the effect of nicotine delivered as a dust. 



Experience covering several years in the application of nicotine as a 

 spray shows that using a mixture composed of 1>^ pints of "Black 

 leaf-40," 8 pounds of soap and water to make 100 gallons, the acre 

 cost for lice treatment should, with the present cost of nicotine, range 

 from $3.50 to about $4.00. The cost may be distributed as follows, not 

 taking into consideration the machine charge;- — Nicotine $2.34 (whole- 

 sale) or $2.91 (retail) , .soap 40c, man labor 50c, horse labor 25c, total 

 $3.49 or $4.06. Experience has shown that to get a kill with nicotine 

 delivered es a dust comparable to that obtained with nicotine delivered 

 as a spray, from 30 to 50 pounds of m.aterial is necessary per acre. The 

 cost of dusting will, therefore, range from $4.75 to $7.50, depending upon 

 the amount of dust used per acre. The cost may be distributed as 

 follows; — Dust material 30 pounds to the acre $4.50 or 50 pounds to 

 the acre $7.50, man labor 17c, horse labor 8c, total $4.75 or $7.70. In 

 making these calculations on both dust and spray it is assumed on the 

 basis of experience that one m.an and a team together with the proper 

 machinery can spray 8 acres a day or dust 24 acres a day. 



It thus appears that nicotine delivered as a dust suffers from two 

 serious disadvantages — rain falling within the period of kill (the first 

 72 hours) seems greatly to reduce if not entirely to stoD the work of the 

 nicotine dust, and the application of nicotine in a dust form at strengchs 

 sufficient to make it as effective as the same substances delivered as a 

 spray costs much more per acre. 



