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amount in the minimum of time, or that it should be less volatile 

 and so act more slowly but for a longer time. The former is the better 

 method, even though it loses its efficiency very soon. 



Almost any cheap, readily available material that is capable of 

 being reduced to an impalpable " smoky " dust, fairly bulky and 

 free from undesirable effects, may be used as the filler. The filler 

 should be finely divided, fairly heavy, and as dry as possible before 

 adding the nicotine, and a material that does not absorb the nicotine 

 readily produces a more quickly acting dust. A light filler is better 

 for large trees Uke walnuts, especially with insects that are easily 

 killed. Brief notes are given on materials that have been tested, and 

 these include kaohn, which in many respects is the best material that 

 has been found. The chief objection to hydrated lime is the irritation 

 it causes to the skin and eyes of the operator. Quick lime produces 

 heat in the reaction, causing the loss of some of the nicotine. Calcium 

 carbonate makes a satisfactory filler when dried and finely pulverised. 

 Calcium sulphate forms hard lumps in drying. Diatomaceous earth 

 tends to cling together in flakes and particles and is very absorptive. 

 Talc is heavy and more expensive, but, when thoroughly pulverised, 

 makes a very good dust and sticks well. Although sulphur is heavy 

 and non-absorptive, it has been shown that when mi.xed with it a 

 given amount of nicotine is more effective against insects than with 

 any other filler mentioned. Only the very finest grades should be 

 used, and it cannot be used on certain crops, especially cantaloups, 

 strawberries and walnuts, in California in the hot weather without 

 danger of scorching. Tobacco dust when well ground is ab^iorptive, but 

 is too expensive as a carrier. 



Various compounds of nicotine have been tested, but with the 

 exception of nicotine oleate none are as effective as pure nicotine. 

 Other poisons have also been tried, but none show promise of success 

 compared with nicotine, except pyrethrum, which is too expensive. 

 The addition of some other substances increases its effect. About 5 per 

 cent, of kerosene may be added to a fairly dry dust without destroying 

 its dusting qualities. Dry lime-sulphur or a similar preparation also 

 increases efficiency. Black-leaf 40, kerosene and dry lime-sulphur 

 form a very powerful dust. In hquid form 0-1 per cent, nicotine is 

 considered a strong mixture, and in dust 10 per cent., and the greatest 

 possibility of reducing the amount of nicotine lies in making it as 

 quickly volatile as possible. The hotter the weather the greater the 

 effect produced by a given strength of dust. The possibihty of reducing 

 the cost of manufacture and of a new type of dusting machine are 

 discussed. 



The following species have been experimented upon with at least 

 promising results : Macrosiphum rosae, L. (rose aphis), Acyrthosiphon 

 [M.) pisi, Kalt. (pea aphis). Aphis gossypii. Glover (melon aphis), 

 A. rumicis, L. (black bean aphis), A. malifoliae, Fitch (rosy apple 

 aphis), Brevicoryne {A.) brassicae, L. (cabbage aphis), Toxoptera 

 aurantii. Boy. (black citrus aphis), Scirtothrips citri, Moulton (citrus 

 thrips), Thrips tahaci, Lind. (onion thrips), Taeniothrips inconsequens, 

 Uzel [pyri, Dan.) (pear thrips), Eutettix tenclla. Baker (beet hopper), 

 Ery throne lira comes, Say (vine hopper), Anasa tristis, DeG. (squash 

 bug), Pieris [Pontia) rapae, L. (cabbage worm), Pseudohazis eglanterina, 

 Boisd. (brown day moth), Hyphaniria citnea, Drury (fall webworm), 

 the butterflies, Lemonias chalcedon, D. & H., Pyrameis [Vanessa) 

 cardiii, L., and Vanessa caryae, Hb., Nysius ericae, Schill. (false chinch 

 bug), N. ericae miniUus, Uhl., Malacosoma spp. (tent caterpillars) and 



