The anthracnose of blackberries is the same as that on raspberries. The appearance of the disease on the various susceptible parts is similar in both cases. The causal organism is also the same.
Recent investigations in Washington have shown that black-berry anthracnose can be profitably controlled by spraying. Two applications are necessary: (1) spray just before the buds open with bordeaux mixture 5-5-50 to which has been added resin-fish-oil soap at the rate of one pound to fifty gallons of the spray. The resin is valuable in rendering the spray more adhesive, and the soap will aid in the control of leaf-hoppers. (2) Spray two or three weeks after the petals fall, using burgundy mixture in place of bordeaux. This substitution is made in order that no precipitate will be apparent after the fungicide has dried on the berries; for coating the berries with a spray that shows at picking - time is objectionable. The burgundy mixture is made from the following formula: copper sulfate (blue vitriol) two pounds, sal soda (washing soda) three pounds, and water one hundred gallons. To this mixture is added one pound of soap to each fifty gallons. The soap should be dissolved and added to the mixture after the spray tank is filled. The mixture should be thoroughly agitated during the spraying operation.
Under Washington conditions, profit from this measure of control is obtained through increased quality and quantity of healthy berries, and by the prevention of cane girdling. The practices of cane removal and spraying in the fall have been found to be unnecessary.
(This disease is more fully discussed under Raspberry, page 406.)
Rees, H. L. Experimental spraying for blackberry anthracnose. Washington Agr. Exp. Sta. Monthly bul. 3:8: 2 - 10. 1915.