414 



wash against the aerial forms. The advantage of nicotine or nicotine 

 sulphate with soap is that it can be applied as a fine spray with very 

 much less pressure than the other washes. In order to destroy both the 

 ascending root forms and the migrants from the elms, spraying should 

 be done at the end of July or in August and not later than the second 

 week in September. 



Dust spraying, which has given considerable success in America, has 

 not been tried to any extent in this country. The only experiment 

 on a large scale against E. lanigerum was with the patent substance 

 known as Belumnite ; its killing power on both Aphids and caterpihars 

 was good, and nearly equal to that of nicotine or nicotine sulphate, 

 water and soap. 



It is of the utmost importance that young stock should be disin- 

 fected before planting ; this can be done by fumigation, using for 

 every 100 cu. ft. of space \ oz. of sodium cyanide, and for each liquid 

 oz. of cyanide, 1 liquid oz. of sulphuric acid, previously gradually 

 diluted with 4 oz. of water, the stock being left in the fumes for at 

 least two hours. It is said that immersion of young stock in petrol 

 kills all woolly Aphids without injury to the trees, while other oils 

 prove fatal to them. Immersion in paraffin jelly proved fatal, but in 

 soft soap and nicotine the root and stem forms were destroyed without 

 harm to the trees. By the fumigation method, however, eggs of the 

 mussel scale [Lepidosaphes ulmi] and all other insects were destroyed 

 at the same time. 



Theobald (F. V.). The Aphides attacking the Potato. — S.E. Agric. 

 Coll., Wye (Advisory & Res. Dept.), 1922, 12 pp., 9 figs. Price Is. 



A study of the Aphids occurring on potatoes in Britain has been 

 made with a view to determining the species that carry the virus of 

 mosaic and curly-leaf diseases. Descriptions are given of the four 

 common species occurring on potato foliage and tubers, viz., Macro- 

 sipkum solanifolii, Ashm., found on potatoes, roses and many other 

 plants, and wintering as ova on roses and as ova and apterae on 

 potato tubers and sprouts and probably on other plants. Though 

 common on potato haulms, it has only once been received from potato 

 seed. This species is probably Kaltenbach's solani, but it is thought 

 advisable to retain Ashmead's name for the present. Myzns persicae, 

 Sulz. [Aphis dianthi, Schr., vulgaris, Kyber, vastaior, Smee, persicaecola, 

 Boisd., persicophila, Rond., malvae, Oestl., and tuheroscellae, Theo.) 

 occurs on almost any plant except conifers and forest trees, and 

 commonly on potato haulms and seed. Normally, eggs are laid in 

 autumn on peaches, nectarines. Daphne, Brassica, and on potato 

 tubers, and may hatch as early as January, potato sprouts often being 

 destroyed by it. It is found nearly all the year round. M. pseudo- 

 solani, sp. n. [solani, Theo., nee Kalt.) is found only on potatoes and 

 is especially abundant on seed potatoes from January to April, 

 occurring also on the bine from August to October. A. solanina, 

 Pass., is found not very numerously in' the apterous stage under 

 leaves. This species does not readily fall on sweeping the bine. 

 A. rumicis, F., is found at times on the bine, but seems to be 

 only a casual pest. A description is given of the subterranean 

 species, Geoica [Tychea) phaseoli, Pa.ss., usually found on the roots 

 of French and runner beans, and occasionally found on potato 

 roots. It is widespread in Britain, but is not considered a serious 

 potato pest. 



