692 PROTECTION AOAINST DISEASES. 



uncovered. In case the earth should be washed away by rain, 

 it must be replaced. 



(c) Nursery-beds should be manured with decomposed 

 beech leaf-mould. This has been strongly recommended by 

 several foresters, and a coating of about 1 to 1^ inches appears 

 to be sutiicient. This prevents sudden wide ranges of tem- 

 perature in the surface soil, though it is not clear on this 

 account why beech leaf-mould is preferable to other similar 

 manure. It is stated, however, that heather-humus when used 

 instead of beech leaf-mould does not prevent needle-cast. 



(/) When 2-year-old plants are used, the yearlings should be 

 lined out in nursery-lines. 



b. Dry Needle-cast. 



The principles to be followed in the case of this variety of 

 the disease should consist in plans for raising the temperature 

 of the soil, and reducing the intensity of the light, in order to 

 increase the activity of the roots and reduce transpiration. 

 Attempts should also be made to increase the powers of 

 resistance of the plants. 



Soil-temjyerature is increased by the following measures : — 



i. Draining wet soils. 



ii. Deep cultivation and manuring, for instance with burned 

 turf, but these measures can be undertaken only in permanent 

 nurseries. 



iii. Raising the level of the soil about 1 foot in places pre- 

 pared for sowing or planting. This method is useful for other 

 reasons, and especially in the case of compact or wet soils. 



iv. Covering the intervals between rows of plants in the beds 

 with substances that are bad conductors of heat, such as 

 moss, dead leaves, etc. 



Intensity of light is reduced as follows : — 



v. Reproduction of Scots pine under shelterwoods, or with 

 lateral shelter. 



vi. Sowing Scots pine with leguminous fodder-crops, such 

 as lucerne or saintfoin. This has given splendid results in 

 Brandenburg and Mecklenburg. 



vii. The hardiness of the plants is increased by giving them 

 plenty of space from the first, by carefully preserving the 



