482 PROTECTION AGAINST FUN<;l. 



C. Seedling and Leaf Fungi. 

 * 6. Phytophthora Fayi, R. Hrt^i. 



(Beech-seedling Mildew.) 

 a. Description and mode of Attack. 



This .very destructive fungus, also named P. omnivora, 

 De Bary, causes great damage among beech seedlings ; these, 

 when affected, turn black and die from below upwards, during 

 their germination or % immediately after the cotyledons have 

 appeared. The little stem shrivels up and turns brown above 

 and below the cotyledons, whilst they are still green, or dark 

 specks appear on the cotyledons or on the young leaves. 

 Within six or eight 'days after the first appearance of the 

 disease, it attacks the whole plant, especially in protracted 

 rainy weather in the months of May and June. In dry 

 weather the attacked plants appear as if singed by fire. It is 

 frequently accompanied by Lachnusfagi, L., a species of aphis. 

 The first infection of the beech by the parasite comes from 

 oospores that have remained in the ground since former 

 sowings. The mycelium, which is intercellular, spreads into 

 the stem and cotyledons, and numerous hyphse break through 

 the epidermis or stomata, and produce lemon-shaped spor- 

 angia. After the bursting of these, fresh sporangia are formed, 

 and the spores are spread in all directions, and in this way 

 the disease may extend over a considerable area of young 

 plants by attacking their cotyledons, or primordial leaves. 

 The development of the fungus is so nipid that in rainy 

 weather and in damp localities, in 3 or 4 days after the first 

 appearance of the disease, sporangia are formed on the host. 

 At the same time, thick-walled oospores are produced sexually 

 within the cotyledons ; these fall to the ground in the rotting 

 tissues, and may then remain alive for four years and more. 

 These oospores reproduce the malady from year to year if the 

 place be used again for sowing beech. In dense sowings on 

 damp soil, the fungus infectg the roots of the plants until 

 whole rows of them die at once. 



Beech natural reproduction in shady woods, beech seed- 

 beds and nursery lines, as well as those of other species, 

 suffer greatly from this lungus. 



