REPORT OF THE BOTANIST 253 



SESSIONAL PAPER No. 16 



so interfered with that a crop of fruit cannot be matured, ©n the leaves, small but 

 similar spots occur which often fall out, leaving a perforation. When the leaf-stalks 

 or leaf-veins are affected, the leaf may develop in a one-sided manner and the margins 

 are often inrolled. The spores are produced in masses in the centre of the older spots. 



Control. 



Treatment consists in going over the plantation as soon as the fruit is picked, 

 cutting out the old canes and any diseased new ones, and burning them. When the 

 disease becomes very bad, a new plantation of healthy shoots must be set out. Spray- 

 ing with Bordeaux mixture to protect the young canes is sometimes recommended but 

 it is doubtful if it is worth while. 



FROST INJURING FLOWERS OF STRAWBERRIES AND RASPBERRIES. 



Practically no year passes without our receiving from fruit-growers, during the 

 time of flowering of raspberries and strawberries, a number of inquiries relating to 

 the cause of what is popularly called ' black heart ' of strawberry or raspberry flowers. 

 The cultivated varieties of these plants are more or less subject to frost injury, which 

 manifests itself by producing a blackened centre in these flowers. In severe cases, all 

 flowers forming a cluster may be found affected, especially in varieties where most 

 of the blossoms open at one time. Night frosts are capable of great injury by destroy- 

 ing the styles of the flowers and thus preventing the fruit from being formed. In some 

 instances, a few styles only may be killed and the result will be a crippled, malformed 

 fruit, which does not recommend itself by its appearance to the buyer. It has been 

 found, especially in the case of strawberries, that the injury may be largely prevented 

 by covering all early-flowering varieties at nights with straw or loose litter of some 

 kind. The harvest may thus often be increased from ten to twenty per cent and more. 

 Raspberries may be planted between sheltering hedges, or they may be covered over 

 night with cheese cloth. Where these suggestions may not be practicable, spraying 

 with cold water early in the morning before the rays of the sun take effect has been 

 proved a useful preventive. 



The lighting of smudge fires and keeping them alive throughout cold nights has 

 also proved quite successful. 



leaf spot of strawberry (Mycosphaerella Fragarios, [Tub] Linden). 



This is the commonest disease of the. strawberry, and is very frequent on both 

 wild and cultivated plants. The spots are of medium size, and show first as a rather 

 indefinite, reddish or purplish discolouration. Later, the dead centre of the- spot 

 becomes whitish or ash-coloured and is surrounded by a rather indefinite area of vary- 

 ing shades of red or purple. They often coalesce to form large blotches. During the 

 summer months, spores are produced on the surface of the pale central portions, and 

 these, under suitable conditions of moisture and temperature, serve to propagate the 

 disease throughout the growing season. During the winter a second form of spores 

 develops within the dead tissues of the leaf, and these are scattered in late winter or 

 early spring. The injury consists chiefly in the destruction of so much leaf tissue 

 and consequent malnutrition of the fruit, but the development of the latter may be 

 more directly affected by the fungus attacking the fruit- stems. 



