345 



tussock -mo til [Heinerocampa], codling-moth [Cydia pomoTiella], and 

 Taxomis glahratus {nigrosoma) (dock saw-fly). 



The usual control measures are given, special stress being laid on 

 the mechanical value of high-pressure spraying. 



Beittain (W. H.). Notes of Two Species of Tree-hoppers (Membra- 

 eidae) ovipositing in the Apple. — Proc. Entom. Soc. Nova Scotia 

 for 1916, Truro, no. 2, January 1917, pp. 34-39. [Received 

 2nd June 1917.] 



Ceresa faurina, Fitch, oviposits in the buds of apple trees, but as it 

 never causes any injury to the bud, even in extreme cases, it cannot 

 be considered of economic importance. The closely allied species 

 C. bi(balus, F. (the buffalo tree-hopper), which oviposits in the twigs 

 and smaller limbs, may, however, cause serious secondary damage 

 owing to the scars made thereby affording suitable conditions for the 

 entrance of boring insects and wood-destroying fungi. 



Sanders (G. E.). Arsenate of Lead versus Arsenate of Lime. — Proc. 

 Entom. Soc. Nova Scotia for 1916, Truro, no. 2, January 1917, 

 pp. 40-45. [Received 2nd June 1917.] 



A spraying mixture of lead arsenate and lime-sulphur has been found 

 imsatisfactory in practice owing to the chemical reactions resulting 

 in the formation of lead sulphide, which settles on the bottom of the 

 tanlc and prevents the proper agitation of the liquid, while it clogs the 

 nozzles and removes over 35 per cent, of the sulphur from solution, 

 5 per cent, of the arsenic oxide at the same time becoming soluble [see 

 this Revieiv, Ser. A, iii, pp. 655-657]. This would be obviated by the 

 use of calcium arsenate, guaranteed to contain less than 1 per cent, 

 soluble arsenic, as there is no reaction between the arsenates of calcium, 

 barium or strontium and sulphide solutions. Arsenate of lead used 

 alone is quite harmless to foliage, but mixed with lime-sulphur is much 

 more injurious than a mixture of arsenate of lime and lime-sulphur. 

 On the other hand arsenate of lime by itself causes the most severe 

 burning owing to the greater affinity of calcium for carbon than for 

 arsenic. Hence in the presence of the carbon dioxide of the leaf, 

 calcium carbonate is formed and arsenic is liberated in the form of 

 arsenic acid. 



As regards the effect of these two arsenates when mixed with sul- 

 phides other than lime-sulphur, experiments have shown that in the 

 case of barium tetrasulphide, a solution of dry (acid) lead arsenate 

 1 lb. to 40£rals., and barium tetrasulphide 3 lb. to 40. gals., slightly 

 scorched 50 per cent, of the leaves ; while a mixture of dry arsenate 

 of lime I lb. to 40 gals, and barium tetrasulphide 31b. to 40 gals., 

 slightly scorched 2 per cent, of the leaves. The combination of sodium 

 sulphide with lead arsenate usually results in scorching all the leaves 

 more or less, owing to the formation of soluble sodium arsenate, but 

 with calcium arsenate a harmless mixture is formed that can be applied 

 three or four times to strongly growing trees. Repeated application 

 to slow-growing trees, however, seems to result in the poisoning and 

 yellowing of the leaves. It still remains an open question whether 

 lead arsenate or calcium arsenate in a lime-sulphur solution has the 

 greater fungicidal value. 



