Insect Pests and Fungoid Diseases. 435 



the autumn from this cause. The development of the fungus is most rapid 

 in a damp, still atmosphere. In the summer the fungus produces large 

 numbers of spores, each of which is capable, under suitable conditions, of 

 acting as a fresh centre for the spread of the disease. On the approach of 

 winter, or other unfavourable conditions, it produces numerous resting 

 bodies, known as Sclerotia, irregular in size and form and brown or black 

 in colour; these germinate in spring and again give rise to the botrytis 

 form. In many plants, such as potatoes and beans, these sclerotia are 

 formed inside the stem. 



Certain other sclerotium-forming fungi (S. bulborum, &c.) attack bul- 

 bous plants, such as the onion, the sclerotia being formed in the scales of 

 the bulb. 



Treatment : Cut off all diseased plants or portions of plants, or any 

 leaves or fruit which may be affected. Do this thoroughly as well as gently 

 and carefully, as any small portion left or any scattered spores may start a 

 fresh epidemic. Burn them at once. Dust the plants and the surface of 

 the soil with lime and sulphur. Keep both plants and surroundings as 

 dry as possible. 



Persistent spraying with Bordeaux mixture or cupram will keep the 

 disease in check. 



The soil should be limed before cropping again. 



STRAWBERRY LEAF SPOT (Sphczrella Fragaricz) This disease 

 first appears as small purplish spots on the leaves. These spots gradually 

 increase in size, and the colour changes to reddish-brown with a purple 

 edging. The disease is often very serious on some varieties. By injuring 

 the leaves its effect is to reduce the crop-bearing powers of the plants, 

 often to a serious extent. 



Treatment : Spray with Bordeaux mixture when growth starts in 

 spring and again when first flowers are open. When crop is gathered cut 

 old leaves, removing and burning them. This is safer than the method 

 sometimes recommended of burning off leaves whilst on the plant. In 

 either case spray new growth two or three times with Bordeaux mixture, 

 at intervals of several weeks. 



STRAWBERRY MILDEW ( Sphcerotheca Castagnei).This appears 

 first as a white cobweb-like growth on the underside of the leaves, and 

 afterwards spreads to the fruit. 



Treatment: Spray with Bordeaux mixture, or dust the plants whilst 

 wet with a mixture of lime and sulphur. See that the spray or powder 

 reaches the underside of the leaves. 



"POTATO DISEASE" ON*TOMATOES (Pkytophthora infestans). 

 Tomatoes grown in the open-air are liable, especially during wet sunless 

 periods in the latter part of summer, to attacks of this disease, sometimes 

 to a serious extent. The symptoms are similar to those found when pota- 

 toes are attacked, i.e., dark brown blotches appear on the stems and leaves. 

 These blotches increase in size and number until, in a bad attack, the 



