SYCAMORE LEAF-BLOTCH. 483 



b. Subjects of Attack, and Distribution. 



The fungus has been observed to attack beech, maple, ash, 

 and robinia, at the seedling stage, and several conifers, especi- 

 ally the spruce and Scots pine. Hence the name " omnivora." 

 The symptoms are similar in these other cases. If only the 

 leaves of the seedling are affected, it may recover, but when- 

 ever the stem is attacked from below, it succumbs. Worms 

 drag down infected seedlings into their holes, and hence gaps 

 sometimes arise in what was formerly a flourishing nursery- 

 bed. 



This fungus causes considerable damage to all the species it 

 attacks, and the spores are transported by wind, mice, roe- 

 deer, and by the tread of men or horses, or even cart wheels. 

 Damp, warm years are favourable to the spread of the fungus. 

 It has been noticed all over Germany. 



c. Protective Rules. 



i. Use Bordeaux mixture, as already described (p. 466). 



ii. Pull up all infected plants and collect leaves lying on 

 the ground as soon as the disease is noticed, and burn them. 



Seed-beds should be carefully watched in May and June for 

 this malady. The workman should wear an apron, in which 

 he places the infected plants, and should take care not to 

 tread on the beds and bury any oospores. Any bed which has 

 been attacked should be examined daily. 



iii. The soil in nurseries may be thoroughly burned, by 

 digging trenches 30cm. deep and 30cm. apart, and filling them 

 with dry brushwood and burning this. Keep the fire going 

 for two days. 



iv. Beech and coniferous seed-beds, where the disease has 

 appeared, should for several years be used only for transplants, 

 and it is then best to change the species grown. 



7. Rhytisma acerinuin, Fr. 

 (Sycamore Leaf-blotch.) 



This fungus causes black spots on the leaves of maples, 

 especially of the Norway maple and sycamore. 



During damp weather in July, round yellowish spots J to 



l I 2 



