413 



them, and two further apphcations at intervals of nine days will kill 

 any larvae that have hatched since and any beetles that have emerged 

 from the ground. The spraying should be done in late afternoon or 

 scorching may result. The egg-masses should be collected and placed 

 in a tray surrounded by water or oil so that the grubs are unable to 

 escape, while any adult parasites that emerge can fly away. Culti- 

 vation of the soil under infested trees destroys many pupae. Numbers 

 of the beetles can be collected by shaking them on to sheets spread 

 under the trees. In slight infestations collection of the eggs, grubs 

 and beetles is sufificient. 



Theobald (F. V.). The Woolly Aphid of the Apple and Elm {Eriosoma 

 lanigeriim, Hausmann). Part n. Treatment. — Separate from 

 //. of Pomology [sine loco], ii, no. 8 [n.d.], 7 pp. [Received 14th 

 June 1922.] 



It has been shown in a previous paper [R.A.E., A, ix, 230] that 

 infestation of apple trees by Eriosoma lanigernm (woolly aphis) 

 goes on year after year between the root system and the stem, and 

 that there is a migration from the over-wintering Aphids on elms. 

 Infestation cannot be eradicated until the root form is exterminated 

 and until the Aphids are killed when away from the elms, so that 

 sexual reproduction in its major aspect is stopped. Evidence shows 

 that the only way to get rid of the root form is by the use of either 

 immune or resistant stock, and spraying should then be done to prevent 

 the return migrants flying back from the apple to the elm. The culti- 

 vation of resistant stock, so successfully practised in America, does 

 not appeal to growers in England, but it is suggested that one of the 

 experimental stations would do well to consider the matter. The 

 relative resistance of various varieties of apple is discussed. Root 

 treatment involves soil injections or the use of soil powder fumigants. 

 Carbon bisulphide is the best fumigant, but owing to the Aphids 

 occurring anywhere from ground level to two feet deep the number 

 of operations necessary renders this method too costly, and even 

 when employed it leaves many living Aphids on the roots. Several 

 patent soil fumigants in solid form were tried without success. Grease- 

 banding the trees to stop infection by the ascending root form has 

 reduced the numbers considerably. Various sprays and washes have 

 been used with more or less success. Paraffin emulsion or paraffin 

 jelly will kill up to 50 per cent, of the insects when there is much woolly 

 covering, and up to 60 per cent, when it is light. These spra3's must 

 be applied with force, and the results are not sufificient to encourage 

 their general use. A wash made of 3 gals, of paraffin, emulsified 

 with 8-10 lb. soft soap in 100 gals, water, with the addition of \ lb. 

 nicotine (96 per cent.), has given as high as 70 per cent, mortality, 

 while 1 oz. of the nicotine to 4 oz. soft soap in 10 gals, of water has 

 destroyed as many as 90 per cent, of the Aphids. The cost of nicotine, 

 however, presents a serious difficulty. Caustic alkali washes used in 

 the winter have been found quite useless. Several of the patent 

 tobacco and nicotine washes proved to be excellent killers, especially 

 those made from tobacco waste. Nicotine sulphate, in the form 

 known as Black-leaf 40, has been found fully as effective as pure 

 nicotine, and costs only half as much. One ounce of this, with 

 4 oz. soft soap and 10 gals, of water was very effective not onl}^ against 

 E. lanigernm, but also against the case-bearer of the apple and plum 

 {Coleophora sp.), and gives greater success than paraffin-nicotine-soap 



