305 



disadvantages of nicotine delivered as a dust are that rain falling within 

 the first 72 hours seems to reduce, if not entirely stop, its action, 

 and the cost is greater than that of a substance that is as effective when 

 delivered in a spray form. A 2 per cent, nicotine clay calcium oxide 

 dust kills 87 per cent, of the Aphids, while under the same conditions, 

 the spray will kill slightly over 85 per cent. A 1 per cent, nicotine 

 calcium oxide dust kills nearly 84 per cent. The maximum efficiency 

 of the dust is reached between 24 and 72 hours after application whilst 

 the spray reaches a high point of toxicity within 24 hours, a great 

 deal being accomplished within the first two hours. The great 

 advantages of the dust are the greater speed with which it can be 

 applied and the independence of a water supply. As a result of 

 experiments with various carriers of the dust it was found that none 

 of the mixtures throw off 25 per cent, of the nicotine within the first 

 72 hours. Although a mixture of clay and calcium oxide appears to be 

 one of the most effective substances in the field, it only throws off 

 about 4 per cent, within the period of toxicity. The amount of calcium 

 oxide used in the field was at least 8^ per cent., whereas in the 

 laboratory tests only 5 per cent, was used. The improvement of the 

 nicotine dust is to be sought in the more rapid evolution of the 2 per 

 cent, or less of nicotine, which is within the range of reasonable practice, 

 or in the delivery of such nicotine as is evolved in close contact with 

 the bodies of the Aphids, or in developing along both these lines. 



Parrot (P. J.). Control of Sucking Insects by Dusting. — //. Econ. 

 Ent., Geneva, N.Y., xv, no. 1, February 1922, pp. 82-85. 



This paper summarises the results of experiments in continuation 

 of previous work [R.A.E., A, ix, 352] with special reference to the 

 susceptibility of apple red bugs and various Aphids. Dusting mixtures 

 containing 6-25, 0-5, 1-0 and 2-0 per cent, nicotine proved toxic 

 to Lygidea mendax, Reut. (apple red bug) and Heterocordylus malinus, 

 Rent, (dark red bug). On the average more uniform results were 

 obtained with the preparations containing the highest amounts of 

 nicotine. The cost of high dosage may be avoided by the careful 

 and liberal application of dusts containing 0-5 or more per cent. The 

 disadvantages of dusts over sprays have already been noticed [see 

 preceding paper]. In large commercial orchards dusting might be of 

 great advantage in a capacity supplementary to the usual spraying. 



Against Myzus ribis, L. (currant aphis), a spray consisting of 1 U.S. 

 pt. nicotine sulphate, 100 U.S. gals, water and 6 lb. soap was used. 

 The dusting preparations contained 0-5, 1-0 and 2-0 per cent, nicotine 

 respectively in a carrier of sulphur lead arsenate (90-10). Jhree 

 treatments were applied at the rate of 1 lb. per bush or 2 gals, of the 

 spray per bush. Both dusting and spraying mixtures afforded efficient 

 protection. The condition of the foliage dusted with 0-5 per cent, 

 nicotine was not quite as satisfactory as in the cases where 1 or 2 per 

 cent, was used. Similar sprays and dusts were also used against 

 Brevicoryne (Aphis) brassicae, L. (cabbage aphis). The most satis- 

 factory mixture appears to be a calcium hydrate preparation containing 

 2-0 per cent, nicotine applied at the rate of 201b. per acre with a 

 hand-bellow duster. Excellent results were obtained with two applica- 

 tions. From 35 to 40 lb. of material were required to produce effective 

 control with power dusting machinery. Nicotine sulphate 5 lb., 

 powdered lead or calcium arsenate 151b. and hydrated lime 801b. 

 is the formula advocated against B. brassicae and cabbage worms 



