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Plant Sanitation- 



effect .whatever upon the foliage, whereas each of the other applications caused 

 scorching and ultimate defoliation. In this experiment, it must be explained, 

 the spraying was done with a garden syringe, and the foliage was more nearly 

 drenched than it would have been by a spraying machine with fine nozzles. 

 But it is almost impossible to prevent men whp do spraying work from drench 

 ing the trees. They are not satisfied with covering the foliage with a fine 

 mist of spray, which is all that is required, and, unless constantly superin- 

 tended, they keep on spraying a tree till the stuff drips off the leaves. 



The third spraying, often necessary to poison the food of leaf-eating 

 caterpillars and to check scab in apples and pears or leaf-blight in plums, is 

 done when the foliage is better able to withstand the effect of Paris green than 

 it is in its half-developed stage. It is much to be regretted, however, that no 

 fungicide has been discovered which will mix harmlessly with lead arsenate. As 

 there is none available, it may be suggested that, in spraying against the Codlin 

 moth, just after the blossom has fallen from apple trees, arsenate of lead alone 

 should be used. Then, if scab be apprehended, Bordeaux mixture can be applied 

 a few days later. Where Codlin moth is not troublesome, a combination, which is 

 at once about the most effective against the apple-sucker and the aphis and 

 a cheek to scab in apples and pears and leaf-blight in plums, is fortunately not 

 liable to cause decomposition. This is a mixture of quassia, soft soap, and potassium 

 sulphide. As the two former ingredients, liberally used, proved strong enough 

 to kill the saw-fly caterpillar on gooseberry bushes last season, completely 

 clearing the infested bushes, they would be equally effective against other leaf- 

 eating caterpillars, at least if the pests were sprayed when young. This mixture 

 would not poison the food of the pests, as Paris green or lead arsenate does, 

 and therefore it would act only upon broods existing at the time of spraying. 

 But in many plantations apple-suckers and aphides on apple trees, and the 

 latter on plums, are much more destructive than any caterpillars, and in 

 such cases this unobjectionable mixture is strongly to be recommended. The 

 strength which proved effective against saw-fly caterpillars was one of 12 lb. of 

 quassia chips and 12 lb. of soft soap to 100 gallons of water. The chips were boiled 

 for an hour in twelve gallons of water with half the soft soap, and after the liquid 

 had been drawn off, the same chips were boiled again with the other half of the soft 

 soap, and the two decoctions were mixed and diluted. To this mixture 6 lb. of 

 potassium sulphide, after being separately dissolved, should be added as a fungicide. 

 If applied just before the leaf-buds on apples and plums open, it may do much to 

 prevent apple-suckers and 'aphides from harbouring on the trees where they are 

 hatched, and possibly to check scab and leaf -blight. The operation may be repeated 

 after the blossom has fallen for the same purposes. The two insect pests by that 

 time will be showing on the trees, if they are to appear at all. Many young cater- 

 pillars also will be killed by this spraying. 



If, in spite of the operations just described, leaf -eating caterpillars are found 

 to be infesting the trees, spraying with arsenate of lead, 3 lb. to 100 gallons of water, 

 may be necessary ; or, if scab is persistent on apples and pears, or leaf -blight on 

 plums treatment with Bordeaux mixture will be beneficial. Prescriptions for the 

 preparation of lead arsenate differ slightly in proportions of constituents. Dr. Dyer 

 states that one pound of dry arsenate of soda to 3 lb. of acetate of lead woidd 

 make tribasic arsenate of lead, the actual quantity of which would be 2J lb. 

 Both constituents should be of 98 per cent, purity. They should be dissolved 

 separately and mixed well. Similarly, the quantity of arsenate of lead to 100 gallons 

 of water varies in different recipes. A Bulletin from Cornell University says to 2 lb. 

 to 8 lb. Another prescription says 2 lb. "or even more, as it does not hurt the foli- 

 age." An excessive quantity of the poison is wasteful ; but, on the other hand, the 



