358 



Sanders (G. E.) cI- Kei.sall (A.). White Arsenic as an Insecticide. — 



Canad. Hortic, Peterboro., Out., Fruit Ed., xliv, no. 4, April 

 1921, p. 55. 



Arsenious oxide, the ordinary white arsenic of commerce and the 

 base from which all arsenical insecticides are made, is the most 

 concentrated form in which to buy arsenic, and its cost is only one- 

 fifth to one-tenth that of other arsenicals per unit of arsenic. Its 

 disadvantages are the difficulty with which it mixes with water, its 

 poor physical condition, its low killing value (as reported by some 

 investigators), and its caustic action on foliage. 



The difficulty of mixing may be overcome in part by using a superfine 

 powder, and it has also been found that a mechanical mixture of white 

 arsenic and some other powder readily miscible in water rapidly goes 

 into suspension. This result may be obtained by mixing dry white 

 arsenic thoroughly with an equal weight of hydrated lime. This 

 mixture is, however, even more caustic than the arsenic alone. On 

 the other hand the copper of Bordeaux mixture has been found to 

 reduce the caustic action to the point of safety. In very few cases, 

 and then only to a very slight extent, would potato foliage be injured 

 by a solution of 1 lb. white arsenic to 101b. or more copper sulphate 

 in 100 gals, water. It was found that if the greater part of the 

 white arsenic goes into solution with the copper, and the ratios of 

 copper and arsenic present are within certain limits, a safe Bordeaux- 

 white arsenic mixture can be produced. The following method is 

 adapted to farm practice : — • 



Superfine white arsenic, guaranteed to pass a screen of 250 meshes 

 to the inch, must be used, with either high calcium or dolomite 

 lime. To make a copper sulphate stock solution, 10 gals, of water 

 are placed in a container and a mixture of 1 lb. of white arsenic and 

 1 lb. of hydrated lime is sifted in. The liquid is well stirred and a 

 bag containing 101b. of crystal copper sulphate suspended in it, 

 stirring being done from time to time. This solution must be made 

 at least 24 hours before it is required ; it will keep indefinitely. It 

 must be stirred before dilution for spraying. 



This formula, which must be strictly adhered to, saves from 60 to 

 90 per cent, of the insecticide cost, and owing to the presence of 

 Bordeaux mixture it encourages the use of a fungicide in spraying 

 potatoes. 



The Tortrix Tea Pest. Lime as a Treatment. [Communique of the 

 Ceylon Dept. Agric, Peradeniya.] — Planters' Chron., Coimhatore 

 xvi, no. 17, 23rd April 1921, pp. 283^-284. 



Experiments with lime as a measure against tea tortrix [Homona 

 coffearia] are being made. At present no definite deductions are 

 possible, but several planters have succeeded in temporarily eradicating 

 the moth by this treatment. The method of application consists in 

 scattering broadcast good slaked lime on the infested bushes, including, 

 when egg-masses are present, the lower sides of the leaves, as the 

 insects feed on the lower surfaces for the first eight days after hatching. 

 The lime should be applied in the early morning, when the bushes are 

 wet with dew, mist, or rain, but not during rain. From 5 cwt. per 

 acre upwards is required, and the applications may be repeated if 

 necessary. Well-scattered lime will remain on the bushes when they 

 are dry, even during moderate rains. 



