REPORT OF THE ENTOMOLOGIST AND BOTANIST. 219 



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of some experiments in treating several kinds of trees early last spring with pure kerosene. 

 His report is as follows : " Much to my astonishment, no ill effects of any moment resulted 

 in the case of any of the trees sprayed with kerosene. In the case of all the trees, 

 spraying was continued just long enough to moisten the plants thoroughly, but not to 

 cause the oil to run down the trunks and collect about the base, and, with the young 

 trees, the soil was carefully mounded up and pressed about the crown to avoid ail 

 danger of the oil collecting at that point." (U. S. Div. of Ent., Bull. 9, iT. S.) 



In view of these facts, it seems impossible to doubt but that if Prof. Smith's 

 instructions are followed carefully we may have in kerosene (ordinary coal oil), a remedy 

 of great value. At any rate, it is well worth the while of any one who has fruit trees 

 infested with San Josd or other scale-insects to risk the losing of one or two trees if he 

 can discover a remedy which will save his whole orchard. Care should be taken to 

 mound up some loose soil around the base of the tree treated to catch any superfluous 

 oil. This should be taken away again after the spraying, to prevent the oil from injur- 

 ing the roots. 



2. Whale-oil soap is the remedy which I have recommended to my correspondents 

 to be applied, as advised by Dr. Howard, in the dilution of only one gallon of water to 

 two pounds of the soap, the trees to be washed or sprayed with the mixture during the 

 winter, some time after the leaves fall in the autumn, and again the foDowing spring, 

 before the buds open. 



One of the chief difficulties with " whale-oil " or fish-oil soaps is the want of uni- 

 formity in their composition. It has been found after many experiments at Washing- 

 ton that what is required for spraying purposes is a caustic potash and fish-oil soap 

 which does not contain more than 25 per cent or 30 per cent of water. Mr. Marlatt 

 states that a brand of soap known as " Good's Caustic Potash Soap No. 3 " is perhaps 

 the best which has been recently put on the market. This is a soft soap, which is 

 shown by analysis to be a true potash soap, containing about 27 or 28 per cent 

 of water. Soaps made with caustic soda have been found unsuitable for spraying pur- 

 poses. Mr. Marlatt concludes his account of the Washington experiments up to date 

 as follows : — " Our examination of the soap question up to the present time seems to 

 indicate that we shall have to insist on a potash soap made with a fair quality of fish 

 or Menhadden oil, and that the water should be eliminated by boiling, so as not to 

 exceed at the outside 25 per cent of the weight of soap. Such soap can be used at the 

 rate of 2 or 2^ lbs. or more to the gallon of water, as a winter wash, without difficulty." 



3. Gas treatment : — For thorough work in treating infested nursery stock, the fumi- 

 gation with hydrocyanic acid gas seems in California to have given the best satisfaction. 

 This method, however, is expensive and the materials used are intensely poisonous. 

 However, for large nurseries where many young trees have to be disinfected before being 

 sent out, this is the best method and is very generally adopted by the large American 

 nurseries. * The plants are placed under a canvas tent made air-tight by painting it 

 twice with linseed oil. The first coat must be quite dry before the second is applied, 

 the size of the tent is immaterial, but it must cover the trees entirely, and its edges 

 should be long enough to lie on the ground, so that the tent may be made perfectly air- 

 tight by having earth thrown upon the edges to prevent the gas from escaping. The 

 latest formula for generating the gas is as follows, for every 100 cubic feet of space to 

 be fumigated : — 



Cyanide of potassium (98 per cent) 1 ounce. 



Sulphuric acid (66°) 1 " 



Water 2 ounces. 



Put the acid and water in an earthenware vessel, large enough to prevent spatter- 

 ing, then place the jar under the tent, add to it the cyanide of potassium and close 

 the opening quickly. The trees should remain exposed to the gas for at least 45 

 minutes, when it will be foiind that insects of all kinds have been destroyed. For the 

 fumigation of nursery stock before shipping, many of the large United States nurseries 



*Full details cannot be given here, but will be supplied on application to any one requiring them. 



