56 THE NURSERY 



the surface raked over constantly when the grubs are near 

 the surface ; they can then be collected and destroyed. 



The grubs bite right through small roots and gnaw the 

 bark from larger roots. 



As regards damage Iby fungi, the most frequent cause 

 of trouble is from Phytophthora omnivera, Hysterium 

 pinastri, and Rosellinia quercina. 



The Phytophthora omnivera is the cause of the " damping 

 off" of the cotyledons of seedling Beech. It also attacks 

 Ash and Maples, and occasionally other seedlings. It is 

 somewhat similar to the " Potato Disease." 



The cotyledons become black and rotten ; and wet, damp 

 weather favours the disease. 



The Hysterium pinastri is the Leaf-shedding Disease. 

 It is most common on Scots Pine when from 2 to 6 years 

 of age, but it also attacks other evergreen conifers. Early 

 in the autumn, black spots appear on the leaves ; these 

 contain the mycelium of the fungus ; next spring, about 

 April, the leaves become brown all over and are shed. It is 

 most common in damp localities, and in crowded nurseries. 



The Rosellinia quercina is the Oak Root seedling fungus. 

 It attacks the roots of Oak seedlings of I or 2 years of 

 age, though occasionally when a few years older. The first 

 signification of the disease is generally the sickly appearance 

 of the leaves of the young plants. But an examination of 

 the roots will probably decide the point. The diseased tap- 

 roots will show small black pustules, about the size of a pin's 

 head. This disease spreads very quickly from plant to 

 plant. When discovered, a trench should be dug round the 

 infected area, and the plants in that area pulled up and 

 burnt, and quick-lime spread over the area and dug in ; and 

 Oak should not be placed on such ground again for some 

 /ears. Other diseases may be mentioned, such as Septoria 

 parasitica on Spruce, Botrytis cinerea on most conifers, 

 and Pestalozzia Hartigii chiefly on Spruce and Silver Fir. 



Wherever any of these three fungous diseases appear, 

 the plants in the infected area should always be at once 

 burnt, and the soil dressed with quick-lime. 



