170 FRUIT INSECTS 



fumigate the stock again with hydrocyanic acid gas before 

 setting. Fumigation with this gas, if properly and thoroughly 

 done, is the most effective and practicable treatment for nursery 

 stock. The dipping of such trees in the lime-sulfur wash or other 

 sprays is not so effective and may injure the trees, especially if 

 the roots are dipped. 



After much experimentation with fumigation tents, whale- 

 oil soap, undiluted kerosene and crude oil, and mechanically 

 mixed oil-water sprays, these have been largely superseded by 

 the cheaper, more effective and safer sprays of oil emulsions, 

 miscible oils and the lime-sulfur wash, which must be brought 

 in contact with each scale. Several applications of a 10 to 

 15 per cent kerosene emulsion spray during the summer has 

 been safely used on apples to check the development of the pest, 

 and a 25 per cent crude petroleum emulsion (formula, p. 486), 

 makes an effective spray for use on old apple trees as the buds 

 are swelling in the spring. The miscible oils should not be 

 diluted more than 1 gallon of oil to 10 or 12 of water to get 

 satisfactory results. The lime-sulfur wash should be used in 

 preference to other sprays on peaches, for when apphed in early 

 spring it kills the scale and also acts as an effective fungicide 

 against the destructive peach leaf-curl fungus. Badly infested 

 trees should be sprayed twice, first in late autumn after the leaves 

 drop and again in early spring before growth begins. Some are 

 able to successfully control the pest with only one application 

 in early spring. The cheapest and safest spray, the one which 

 has withstood the severest tests of experimenters and orchard- 

 ists, and has given the most uniformly successful results, is the 

 lime-sulfur wash. The oil emulsions or miscible oils are non- 

 corrosive, more agreeable to use, spread better, so that less 

 material is necessary, and they penetrate more effectively the 

 crevices of the bark or the fuzzy coated twigs of apple trees, but 

 unless properly applied there is always more or less danger of 

 injuring the trees. The market brands of miscible oils are simply 



