The Canadian Horticulturi^ 



Vol. XXXI 



DECEMBER, 1908 



No. 12 



Fungous Diseases of Ontario Orchards* 



M. B. Waitc, Pathologist in Charge, Investigations of Diseases o! Fruits, U. S. Department of Agriculture 



I AM called upon to discuss two very 

 comrrion and destructive diseases of 

 the orchard, — peach yellows, the most 

 dangerous and deadly disease of the 

 peach tree ; and pear blight, the contag- 

 ious and destructive disease of pomac- 

 eous fruits. Neither of these diseases is 

 preventable by spraying. I will precede 

 this discussion with a short account of 

 the treatment of some of the prevailing 

 fungous diseases in this section and will 

 tell something of sulphur as a fungicide, 

 particularly the new self-boiled lime- 

 sulphur mixture. 



SULPHUR vs. COPPER AS A FUNGICIDE 



Although both sulphur and copper 

 have been known to possess the proper- 

 ty of killing fungi for many years, sul- 

 phur antedates copper as a practical 

 fungicide. It was, in fact, in use long 

 before the year 1885 (?) when the word 

 "fungicide" was coined. The discovery, 

 widely published in 1885, by Millarde of 

 Bordeaux, France, of the remarkable 

 fungicidal properties of the copper-lime 

 mixture, put copper far in the lead as a 

 useful fungicide. Since that time it has 

 been brought out that the practicability 

 of this mixture depends not alone on the 

 copper. It is the peculiar combination 

 of copper and lime and its resulting pro- 

 perties that gives it its value. Since that 

 time much experimenting has been done 

 with other compounds, mainly of copper, 

 yet to this day no compound of copper 

 has been found approaching it in value. 

 The peculiar properties of Bordeaux mix- 

 ture are that it is harmless or nearly 

 harmless to most plants when sprayed 

 on them during active growth, it sticks 

 tightly for weeks and ev-n months on 

 the plant after it is applied, it is nearly 

 insoluble and yet will dissolve just 

 enough in rain water to give this suffic- 

 ient copper to kill most fungi. There is 

 no trouble in finding poisons and chem- 

 cais that will kill the fungi ; the problem 

 is to find poisons sufficiently insoluble 

 .so as not to hurt the plant and yet con- 

 tinually to give off just enough of the 

 fimgicidal material to do the work when 

 needed. 



With sulphur that we have had avail- 

 able for use, either the extremely solu- 

 ble compound, like the boiled lime- 

 sulphur wash, which scorches or burns 

 living plants, the liver of sulphur, which 

 has to be used extremely dilute when 

 applied to the foliage and which is read- 

 ily soluble so that it washes off with rain, 

 or else the comparatively insoluble flow- 

 ers of sulphur. The latter substance is 

 not sufficiently active as a fungicide to 

 be used alone. 



SELF-BOILED LIME-SULPHUR WASH 



Recently, through the investigations 

 of Mr. W. M. Scott, of the United States 

 Deipartment of Agriculture, the peculiar 



A Suggestion for Christmas 



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 It is something that will interest 

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 special Christmas announcement 

 on inside front cover. 



•A portion of -a paper read at the Toronto con- 

 vention of the OAtario Fruit Growers' AsBocia- 

 tloii, held last month. Pear blight and poach yel 

 Iowa will be dealt with in the next issue. 



value and desirable properties of the self- 

 boiled lime-sylphur wash have been dis- 

 covered. This mixture is very simply 

 made by adding the flour or flowers of 

 sulphur to the lime before slaking. No 

 heat is used except the heat produced by 

 the slaking lime. The value of the pre- 

 paration was discovered by Mr. Scott in 

 seeking a remedy for brown rot of the 

 peach. He found not only that this mix- 

 ture was an excellent fungicide, prevent- 

 ing the brown rot and black spot of the 

 peach, but when properly made with a 

 small quantity of soluble sulphides, it 

 could be applied to peach foliage with 

 perfect safety. For the first time, then, 

 we have a practicable fungicide, with 

 fairly good sticking qualities, slowly sol- 

 uble and not injurious to peach foliage. 

 It may also be sprayed on the .sensitive 

 Japanese plums. This important discov- 



257 



ery was made in the season of 1907 and 

 very satisfactory results were obtained. 

 In the season of. 1908 they were repeated 

 by Mr. Scott and his assistants, and 

 by some other investigators and great 

 success was attained in the prevention of 

 several of our leading diseases. This 

 gives us practically a new fungicide 

 which is in many ways a rival of Bor- 

 deaux mixture. It does some of the 

 things that Bordeaux mixture will not - 

 do ; on the other hand, it does not quite 

 equal Bordeaux mixture as a fungicide, 

 and unless a better form is discovered 

 than we have available now, this mixture 

 should not displace the standard Bor- 

 deaux, except where the latter is in- 

 jurious. 



The important point has been gained 

 that in the treatment of peach diseases 

 where the use of Bordeaux mixture or any 

 other copper compound had to be aban- 

 doned we still have a most excellent and 

 thoroughly practical fungicide. From 

 the results obtained from recent experi- 

 ments, it is quite probable that on the ' 

 Ben Davis and possibly even on the' 

 Baldwin apple, where russetting by Bor- 

 deaux is a serious matter, we can still 

 spray our fruit with a fungicide that will 

 give satisfactory results. 



Furthermore, attention should be called 

 to the fact that this sulphur spray, while 

 slightly inferior to Bordeaux mixture, is 

 a most excellent insecticide, especially 

 for certain types of insects. It is the 

 deadly enemy of mites and scale insects. 

 The self-boiled lime-sulphur mixture was 

 tried as a scalecide on dormant trees and 

 put in the background by the more active 

 form 6f sulphur in the boiled lime-sulphur 

 wash, but it looks as though we had here 

 an excellent scalecide, thoroughly satis- 

 factory for use when the trees are in fol- 

 iage, in addition to its other merits as a 

 fungicide. It is expected that the ento- 

 mologists will work out the exact status 

 of this spray as an insecticide. However, 

 at the present time they do not advise 

 its use as a dormant spray. 



FACTORY-BOILED LIME-SULPHUR 



Recently several of the chemical manu- 

 facturing firms have put on the market 

 stock solutions of the boiled limc-sulphur ' 

 wash. The.se are more perfectly pre- 



