452 PROTECTION AGAINST FUNGI. 



where in a mature crop of 240 trees per acre, on the average 

 14 16 trees are cankered. It is common in Windsor Forest. 

 The fungus also attacks Abies picta, Forb., A. balsamea, Mill., 

 A. Nordmanniana, Lk., A. cephalonica, Loud., and A. Pinsapo, 

 Boiss. Cankerous stems are found on every soil and locality, 

 but the disease is less prevalent on sandy soils arid at high 

 altitudes than on loam or in or near the plains, where the 

 progress of the disease is more rapid. 



The damage in old woods is greater than in young ones on 

 account of the increase in value of the trees, and in pure high 

 forests than in mixed selection-forests. 



c. Protective Rules. 



Mix other species not subject to the disease with the silver-fir. 



Prune off the witches-brooms, which chiefly appear on young 

 trees, by sawing off infected branches close to the stem before 

 the spores are dispersed, and tarring the wounds. 



Kemove cankerous stems in thinnings and preparatory 

 fellings, and transport them speedily from the forest. Even 

 dominating cankerous trees should be removed, and dominated 

 trees left to replace them. Those cankered all round should 

 be first felled, as the crop must not be overthinned from fear 

 orwindfall. 



Old woods full of cankerous trees should be felled before the 

 prescribed period. The group-system practised in Baden 

 allows this to be done, and it is the most effective remedy. 



Weed away Stellarias and Cerastia from the neighbourhood 

 of silver-fir woods, and do not grow silver-fir near the outer 

 boundaries of such woods. It is probable that the disease 

 originates otherwise, besides from infection from the weeds 

 referred to. 



*9. Nectria Cucurbitula, Fr. 



(Spruce Nectria.) 

 a. Description and mode of Attack. 



This fungus produces the spruce-bark disease, and more 

 rarely attacks the Cembran pine and larch. Its external 

 symptoms are : Pale colouring of the needles, the bark and 

 bast turning brown and drying up, generally after insect 

 attacks, and less frequently after wounds from hail or other 

 causes. Numerous clusters of little red, gherkin-like sporocarps 



