362 



than sprayed fruit, but on the other hand it will be more spotted with 

 apple scab. The extent to which this will develop in spite of dusting 

 will depend on the season, the fruit being efficiently protected by 

 this method in all but the severest outbreaks. This being so, owners 

 of large orchards may be advised to take the risk of loss during a 

 year of exceptional scab infestation, the risk being more than counter- 

 balanced by the advantage gained by covering the whole orchard 

 often and at the proper time. The small fruit-grower, on the contrary, 

 might be well advised to adhere to the slower, but rather more certain 

 method of hquid applications. 



Sanders (G.E.). Control of Orchard Insects. — Canadian Horticulturist, 

 Toronto, x\i, no. 5, May 1918, p. 118. 



Fungicides mixed with poison solutions exert a very appreciable 

 influence on the killing value of sprays! Bordeaux mixture added to 

 the average poison decreases its killing value by about 50 per cent. 

 When rapid killing is desired and a fungicide is necessary, a poisoned 

 Bordeaux spray may be made of : — 1 lb. sodium arsenate dissolved 

 in water, the solution being used to slake 5 lb. fresh stone Ume and 

 then made up to 20 gals. ; 4 lb. copper sulphate is then dissolved 

 in another 20 gals, water and the two are poured together. The 

 sodium in this combination causes the arsenic to act rapidly, offsetting 

 the action of the Bordeaux in this respect. 



Lime-sulphur and barium tetrasulphide reduce the killing value of 

 poisons by 15 to 20 per cent., an amount which is neghgible in prac- 

 tice. When large quantities of poisons must be used against biting 

 insects, it has been found injurious to the foHage to add large quantities 

 of fungicides to them, as the lead arsenate so used breaks up and 

 forms so much soluble arsenic, while calcium arsenate used in excess 

 is not sufficiently protected from the air by the sulphide solution. 



Sodium sulphide and potassium sulphide, on the contrary, increase 

 by from 10 to 15 per cent, the killing value of poisons that can safely 

 be used with them. This makes sodium sulphide a most valuable 

 carrier for poisons where outbreaks of canker worms and such insects 

 have to be dealt with, a mixture of 2 lb. soluble sulphur and 2 lb. 

 calcium arsenate to 100 gals, water having been used in such outbreaks 

 with the greatest success, the only ill-effects from one application 

 being 1 to 10 per cent, of yellow leaf. In ordinary practice a decrease 

 of the amount of calcium arsenate with sodium sulphide to Ij lb. 

 per 100 gals, and the addition of 15 to 25 lb. hydrated hme is 

 recommended. 



In cases of outbreaks of biting insects apphcations of simple lead 

 arsenate are recommended rather than combinations, and this at the 

 rate of 10 to 15 lb. standard paste soon after the larvae emerge. As 

 this strength of lead arsenate is at least equal to lime-sulphur or soluble 

 sulphur as a fungicide, it may safely be used alone at double or triple 

 strength at any of the five spraying periods when an outbreak of biting 

 insects is threatened. 



The killing value of four standard poisons which, when they are 

 used alone, is 100 per cent., when they are mixed with sodium 

 sulphide is 1131 per cent. ; with lime and sulphur is 80-8 per cent. ; 

 and with Bordeaux is 56 '5 per cent. 



