The Canadian Horticulturi^ 



Vol. XXXIII 



FEBRUARY, 1910 



No. 2 



Lime-Sulphur vs. Bordeaux for Summer Spraying' 



L. Caesar, Ontario Agricultural College, Guelph 



BEFORE proceeding to the discussion 

 of the value of lime-sulphur as a 

 summer spray for apple and pear 

 orchards let us first briefly call to mind 

 the main fungous diseases of apple and 

 pear orchards that require a summer 

 treatment. In apple orchards the main 

 one is clearly apple scab or black spot, 

 as it is sometimes called. Less impor- 

 tant diseases are the leaf spot and Bald- 

 win spot. Black rot canker is a very 

 . serious disease attacking the trunk and 

 branches but its main treatm.ent must be 

 before the buds burst ; yet, as the sum- 

 mer treatment is also important we shall 

 include it in our list. In pear orchards 

 we shall only deal with pear scab, omit- 

 ting the different kinds of leaf spot, be- 

 cause these are not often serious and 

 lime-sulphur has not been tested on 

 them. Pear blight, twig blight or fire 

 blight, which are all the same disease, is 

 not caused by a fungus and apparently 

 cannot be controlled to any appreciable 

 extent by spraying, so it is omitted. 



In spraying for any of the above men- 

 tioned diseases it is clear that no mix- 

 ture can be given a fair chance unless 

 it is applied at the right time and in a 

 thorough manner. Hence a word or two 

 about these points. 



To prevent most fungous diseases the 

 spray mixture must be applied before 

 the disease gets any chance to make 

 headway ; in short, it should be applied 

 early enough to prevent the spores get- 

 ting a chance to germinate. Hence the 

 date of the first application is usually 

 of special importance. For apple scab 

 the first spraying should be shortly be- 

 fore the blossoms open. If left until the 

 blossoms fall the disease gets a great 

 start for the first signs of it are on the 

 leaves about the time of the opening of 

 the first blossoms. The Second .spraying 

 should be just after most of the blos- 

 soms have fallen, which is the proper 

 time to spray for codling moth ; the 

 third, either two or three weeks later. 

 Of these three applications the first and 

 second are by far the most important 

 and should never be omitted. 



Leaf-spot and canker are controlled by 

 the same sprayings as the scab, except 

 that canker requires a special spring ap- 



* A portion of a paper read at Ihe last Convention 

 of tlie Ontario Fruit Growers' Association. It will be 

 continued in next issue. 



plication in addition to these. It should 

 be noted that leaf-spot is usually caused 

 by the same fungus that causes the 

 canker, namely, the black rot. 



Baldwin spot appears much later in 

 the season and so requires separate 

 treatment. The first spraying for it 

 should be about July ist and the second 

 about two weeks later. It is seldom, 

 however, that it is so severe in Ontario 

 as to make spraying necessary. 



Pear scab begins earlier than apple 

 scab and so requires that the first spray- 

 ing should be made just as the buds are 

 ready to burst. The second application 

 should be just before the blossoms open, 

 the third at once after the blossoms have 

 fallen and the fourth about three weeks 

 later. The early first application seems 

 to be necessary for even fair results. 



We all know that it is not only ne- 

 cessary to spray at the right dates but 



Constantly Improving 



Congratulations on the steadily 

 increasing value of The Canadian 

 HoRTici LTURiST.- — W. A. Mac- 

 Kinnon, Canadian Trade Com- 

 missioner, Birmingham, England. 



also to do it thoroughly. Most of us 

 who have done much spraying know that 

 it is very seldom that a really thorough 

 job is done. The trees are often only 

 half sprayed. Perhaps this in a number 

 of cases is due to the old motto: "Stop 

 spraying just before the leaves begin to 

 drip." This is not a safe motto and our 

 first rule should be: "Make sure that 

 every leaf and fruit is thoroughly cov- 

 ered;" and second, "try to do this with 

 as little waste as possible." One cannot 

 emphasize this thoroughness too much. 

 No man deserves real good results with- 

 out it nor indeed is he likely to get them. 



BORDEAUX vs. LIMK-SULPHUR 



Now let us pass to the mixture and 

 the results. Bordeaux has for so long 

 been the standard fungicide for all the 

 above-named diseases of the orchard that 

 it sounds almost startling to us at first 

 to hear that it has a close rival in lime- 

 sulphur. This wash either in the com- 

 mercial or self-boiled form has been con- 

 siderably experimented with in apple or- 



23 



chards as a summer wash especially the 

 last two years. The results given are 

 sufficiently good to show that it has much 

 merit as a fungicide for apple diseases. 

 They do not, however, show that it is 

 a better fungicide than Bordeaux^ so that 

 those who "swear by Bordeaux" may 

 still continue to do so. 



SPRAYING FOR APPLE SCAB 



Taking up first the results upon apple 

 scab: Prof. W. M. Scott, of Washing- 

 ton, D.C., and Dr. Brooks of New 

 Hampshire Experiment Station have 

 each made a good many careful tests 

 of both the self-boiled and commercial 

 lime-sulphur upon this disease. Each 

 report the commercial wash as giving 

 almost as good results as Bordeaux. The 

 self-boiled in last year's experiments, 



(1908) did not give quite so good results 

 although it showed a fair degree of merit. 

 It was, however, made with cold water 

 instead of hot, which would almost cer- 

 tainly have given better results. I have 

 not seen the reports of this year's work 



(1909) but from Dr. Waite's remarks at 

 the American Pomological Society con- 

 vention held at St. Catharines, I infer 

 that Professor Scott has been much 

 pleased with the way the self-boiled mix- 

 ture has also controlled the scab. 



In experiments conducted by myself 

 at Guelph this summer I sprayed eight 

 fairly large Snow apple trees with the 

 Vanco brand of commercial lime-sulphur. 

 The west side received the three applica- 

 tions at the times mentioned above, the 

 east side owing to my enforced absence 

 had to go without the middle spraying. 

 For the first application a strength of 

 one to twenty-five was used. This burn- 

 ed the leaves slightly so one to forty was 

 used for the other sprayings and no in- 

 jury resulted. The spraying was very 

 thoroughly done. In September the 

 fruit was examined and on the west side 

 where three sprayings were given less 

 than one per cent, of it was scabby ; on 

 the east, where the important spraying 

 just after the blossoms fell had to be 

 omitted, nearly fifteen per cent of the 

 apples were scabby. The fruit moreover 

 was free from russeting and the surface 

 smooth and glossy. Similar results have 

 been reported to me by correspondents. 

 .So that there is practically no doubt that 

 (Continued on page :S!)) 



