248 EXPERIMENTAL FARMS 



1-2 EDWARD VII., A. 1902 



erude oil should not be used in a higher percentage than 20 per cent. The safe limit 

 for plums and pears seems to be 25 per cent, and for apples 30 per cent may be used. 

 For peach trees, Mr. Fisher believes that not more than one quart of crude oil, costing 

 two or three cents, should be applied to each average-sized peach tree, whether this be 

 applied undiluted by means of a very fine specially prepared nozzle or in a mechanical 

 mixture. The only purpose of the water in such a mixture is to act as a vehicle for the 

 oil by which it may be distributed over a wider area as a very thin film. The water 

 evaporates almost immediately and leaves the oil on the trees. For this reason it is 

 important not to go over the same part of the tree twice as has sometimes been done 

 with ill effects by thoughtless operators. 



' Freeman, Ont. — The specific gravity of the Canada crude oil used against the 

 scale was 39£° to 30°, and that of the Pennsylvania crude oil was 44*°. The Canada 

 oil killed the scale and protected the trees from re-infestation better than the American 

 oil, but was also slightly more trying to the peach trees. Japan plums were not in- 

 jured by 25 per cent Canada oil with water, and in one instance two applications were 

 made, the second two days after the first. The only case of injury that has come to my 

 notice from the use of crude oil on plum trees was when it was used undiluted, and in 

 this case Japans and the Egg varieties alone suffered.' — George E. Fisher. 



3. Fumigation. — Undoubtedly the most effective remedy for small trees or bushes is 

 fumigation with hydrocyanic acid gas which will destroy every living scale without 

 injury to the plant. For small trees this has proved most useful, but for large trees 

 the necessary tents and apparatus are expensive, easily injured, and handled with diffi- 

 culty, particularly when there is a wind blowing. There are also difficulties which are 

 yet to be overcome in the way of getting the gas equally diffused beneath large tents. 

 Mr. George E. Fisher has done good work by using inverted tight barrels as gas cham- 

 bers for fumigating bushes and small trees. These were ordinary tight apple barrels 

 each of which contained 4^ cubic feet of space and for which 1\ grammes of cyanide 

 of potassium, 2 grammes of sulphuric acid, and 3 grammes of water were used to 

 generate the necessary gas. In a few instances double quantities were used without 

 any injury to the trees. Larger trees were covered with tents. Mr. Fisher says : — 

 1 We used cyanide 20-100 and 25-100 of a gramme to the cubic foot of space inclosed, 

 mostly 25-100, though I think that 20-100 did just as effective work in September as 

 did 25-100. The 20-100 was exposed 35 minutes and apparently killed all of the scale. 

 Most of the trees treated with 25-100 were exposed 45 minutes without injury and 

 20-100 killed the scale at 35 minutes in September. I still think there is a lot in the 

 time of year this work is done. Prof. Lowe, of Geneva, New York, says he used cyan- 

 ide in various strengths from last December to June, 18-100, 25-100 and 30-100. The 

 25-100 had no effect in killing the scale during low temperatures, and 30-100 used at 

 the same time killed it all — exposure in both cases 45 minutes. In June 18-100, ex- 

 posure 30 minutes, killed all of the scale. This bears out my contention that the scale 

 is much more susceptible to the gas treatment when it is active than when dormant. 

 It also goes to show that a stronger gas will kill it in very cold weather, which I have 

 doubted, but which I shall take some pains to prove this winter.' 



In practice it may be found convenient not to trust solely to any one of the above 

 remedies, but to use a combination of two or more, in accordance with the difficulties 

 which in treating any orchard may arise from many causes, dependent upon the local- 

 ity, the size of the trees, or the facilities for obtaining materials. For small trees 

 fumigation will probably be found most convenient and for large ones spraying with 

 Whale-oil Soap or Crude Petroleum after the trees have been pruned of all unnecessary 

 wood. 



When judging the conditions of trees which have been infested by scale, or which 

 have been treated for its eradication, it is necessary to consider, first, what the condi- 

 tion of the trees is at the time, and also what state, judging from surrounding trees, 

 they would have been in if nothing had been done to relieve them. It is not always 



