- 552 - 
One of the factors involving retardation or acceleration of nicotine 
evolution from a dust carrier is the size of its particles, the gas 
escaping more rapidly from coarse material; the ordinary 100-mesh 
dolomite gives about the average evolution. The fact that under certain 
conditions, especially with high temperatures, sulphur and nicotine 
dust is equal to or "better than hydrated lime and nicotine dust might 
he explained "by the difference in structure or compactness of the 
particles. The thickness of the film of nicotine on the particle 
makes a difference in the rate of nicotine gas evolution, and within 
limits thinner films give off gas more rapidly. High atmospheric 
moisture appears to retard nicotine evolution. Under semi-arid 
conditions free nicotine appears to he far more effective than nico- 
tine sulphate. 
"The percentage of kill and percentage of reduction of the aphids 
very with the late of evolution of nicotine gas; when the rate of gas 
evolution is practically constant, the use of higher-content dusts 
is likely to he followed by a higher percentage of kill and reduction, 
because the charge in the atmosphere about the insects is greater." 
HORSFALL, J. L. (2313) 
1224. THE CONTROL OF PLANT LICE ON VEGETABLES. Pa. Agr. Expt. Sta. 
Bull. 186, 16pp., illus. [Abstract in Rev. Appl. Ent. (A) 12: 328. 
1924.] 
The spinach aphid ( Myzus persicae Sulz.) and the false cabbage 
aphid ( Aphis pseudob rass icae Davis) are easily controlled by nicotine 
sprays or dusts. Spraying is cheaper, the formula recommended being 
1 l/2 pt. 40-percent nicotine sulphate, 5 lb. laundry soap and 100 gal. 
water. In dusting the best results were obtained with free nicotine 
dust containing 1.25 percent actual nicotine and nicotine sulphate 
dust containing 2 percent actual nicotine. The following formulas are 
recommended: 95 lb. superfine hydrated lime to 5 lb. nicotine sulphate; 
or 50 lb. superfine hydrated lime, 45 lb. dolomite and 5 lb. nicotine 
sulphate. The amount of dust applied per acre ranges between 30 and 
50 lb. 
KELSALL, A. (2314) 
1924. DUSTS AND DUSTING IN CROP PEST CONTROL. Sci. Agr. 5 ( 2) : 37-51. 
[Abstract in Rev. Appl. Ent. (A) 12: 540. 1924.] 
Dusting machinery may be used to project vapors of nicotine, 
tetrachloroethane, and hydrocyanic acid. 
PARROTT, P. J., end HARMAN, S. U. (2315) 
1924(?) COMPARATIVE EFFICIENCY OF DUST AND SPRAY MIXTURES IN CONTROL- 
LING THE CURRANT APHIS. N. Y. Agr. Expt. Sta. Bull. 517, 21 pp., 
illus. [Abstract in Rev. Appl. Ent. (A) 13: 30-31. 1925.] 
