186 



SCIENTIFIC AGRICULTURE. 



February, 1922. 



Apple Tree Anthracnose or Black Spot Canker Control 



By E. W. WHITE, 

 District Horticulturist, Department of Agriculture, Victoria, B. C. 



This disease is prevalent in practically- 

 all apple orchards of the coast districts of 

 Oregon, Washington and British Columbia, 

 where control mea;iures are not regularly 

 adopted. It is perhaps the most serious 

 fungous disease with which the coast fruit 

 grower has to deal, and during the past 

 twenty-five or thirty years has caused the 

 destruction of a great number of apple 

 trees with corresponding financial loss. 



It is not the intention in this paper to 

 discuss the origin or life history of this 

 disease or the proper scientific name by 

 which it should be known, but rather to 

 .give briefly the results of five years ex- 

 perimental work in the control of this 

 trouble carried out in the Keating district 

 near Victoria, Vancouver Island, B. C, 



In past 3'^ears the general recommenda- 

 tion given to our growers for the control of 

 this disease was to spray with double 

 strength Bordeaux (8-8-40) as soon as the 

 fruit was picked and before the fall rains 

 commenced. Where this system of spray- 

 ing was followed out very efficient results 

 were obtained, especially on early varieties 

 of apples, and even on late varieties in a 

 good many cases the disease was held in 

 check where the spraying was done thor- 

 oughly. 



The trouble with this control measure, 

 however, was not due to the inefficiency 

 of the spray, but to the fact tliat the har- 

 vesting period is always a busy time for 

 fruit growers and in the majority of cases 

 early varieties were not sprayed when the 

 fruit was harvested; by the time the late 

 apples were picked the wet weather had set 

 in and it was often very difficult to get 

 a fine day on which to do the spraying. In 

 consequence infection took place and each 

 year more dead wood could be found in the 

 orchards. 



Our growers Avere becoming discouraged 

 in their efforts to control the disease and 

 were claiming tliat it could not be done 

 economically and efficiently. 



Consequently in the fall of 1916 the 

 Horticultural Branch in co-operation with 

 J. W. Eastiliam, Provincial Plant Patholo- 



gist, decided to do some experimental, or 

 perhaps better, some demonstration spray- 

 ing. • 



In outlining the work we were very 

 grateful for information' relative to the 

 success achieved in controlling the disease 

 by Leroy Childs, Director of the Hood 

 River Experiment Station, by combining 

 a Bordeaux spray with the last codling 

 moth spray. 



It was confidently felt that the disease 

 could be controlled on early apples and 

 for that reason a late variety was chosen 

 with which to work. A block of 36 twenty- 

 year-old Baldwin trees was selected in the 

 orchard of Tanner Bros., Keating. These 

 trees were very badly diseased and the 

 owners had threatened to cut them out on 

 numerous occasions ; in fact, the disease was 

 so bad that practically every bit of new 

 wood which grew each year would be gird- 

 led by the canker the following spring. 

 Nothing but the bare framework of the 

 tree and innumerable dead shoots were left 

 to constitute the tree. In 1916 the trees 

 were carrying a very light crop of fruit, it 

 being the off-j^ear for bearing. 



In planning to applj' a weak Bordeaux 

 spray early, while the fruit was still on the 

 tree, it was thought that it would be neces- 

 sary to wipe the fruit before marketing 

 but this was found to be unnecessary. 



The -block of trees w^as laid out in four 

 plots, the first nine trees in each row con- 

 stituting Plots 1, 2, and 3, and the last 

 three trees in each row constituting Plot 4, 

 or check-plot. Plot 1 received only an 

 early spray of weak Bordeaux 3-4-40. Plot 

 2 received an early and late spray of weak 

 Bordeaux 3-4-40 and strong Bordeaux 6- 

 6-40. Plot 3 only received the late spray 

 of strong Bordeaux 6-6-40. Plot 4 was the 

 check plot and received nothing. 



In 1916 the first spray of 3-4-40 Bor- 

 deaux was applied on September 6th, after 

 a very dry summer, to Plots 1 and 2, con- 

 stituting 18 trees; 80 gallons of spray 

 mixture were used, averaging 4.44 gallons 

 per tree. 



