172 Commercial Gardening 



equally well marked on both surfaces of the leaf. These patches continue 

 to increase in size, usually retaining a more or less circular outline, and 

 often run into each other. By degrees the centre of each patch becomes 

 greyish, or often almost white, and is bounded by a reddish border, which 

 is often quite bright in colour during the autumn. The pale central por- 

 tion soon becomes covered with minute tufts of the summer fruit of the 

 fungus, once known as Ramularia tulasnei and supposed to be the only 

 form of fungus connected with the disease. The dispersal of the summer 

 spores causes the disease to spread rapidly during dull, damp weather. 

 Later in the season the winter form of fruit appears on the pale patches. 

 These dead patches do not fall away from the leaf, but persist until the 

 leaf actually decays, when the spores are liberated. 



When the disease appears early in the season, the crop of fruit is much 

 reduced both in quantity and in quality, The plants are also weakened 

 for the following season. 



The most certain way of dealing with Strawberry beds that have been 

 diseased is to mow off the leaves soon after the fruit has been picked, and, 

 when the mown leaves are fairly dry, to cover the whole bed with a 

 sprinkling of straw, litter, or other convenient material that will burn well, 

 and set it on fire. By this method not only are all diseased, spore-carrying 

 leaves destroyed, but also dead fragments of leaves and spores lying on the 

 ground. The destruction of many injurious insects is also included. 



During the spring following the burning, the plants should be sprayed 

 with sulphide of potassium, commencing when the leaves are quite young. 

 Spraying should be continued at intervals until the blossom begins to open. 

 If this procedure is followed the disease can be eradicated. 



Strawberry Mildew (Sphcerotheca humuli). This pest has long been 

 known as an enemy of Strawberries, both cultivated and wild plants 

 suffering equally. This same fungus is also the cause of the still more 

 serious " Hop Mildew ", and is also more or less common on about twenty 

 kinds of British wild plants, hence the opportunities for cultivated plants 

 becoming infected are ample. Fortunately, in the case of Strawberries, only 

 the leaves, as a rule, are attacked, and that usually somewhat late in the 

 season. When the leaves are attacked the edge bends upwards, exposing 

 a considerable amount of the under surface of the leaf, which, on careful 

 examination, is seen to be more or less covered with a very delicate, 

 whitish mildew, which is powdery here and there, due to the accumulation 

 of the summer spores of the fungus. When the fungus attacks the foliage 

 early in the season, before the flowers expand, the mildew passes on to the 

 fruit, which usually becomes entirely covered with a white mildew. The 

 fungus does not usually retard the growth or ripening of the fruit, but it 

 renders it absolutely useless being devoid of all sweetness, and having 

 an insipid and watery taste. It is not unusual to meet with fruit on sale 

 that has been rinsed in water to get rid of the mildew; but it presents a 

 dull, waterlogged appearance, and, as stated above, is worthless for eating 

 or jam making. 



