464 



PKOTECTION AGAINST FUNGI. 



November assume a golden-yellow colour, and swell up 

 slightly on one or both sides of the mid-rib ; the fungus 

 hibernates on the tree in this condition. The swelling 

 becomes greater at the beginning of spring, and from April 

 to the middle of May the epidermis of the needle bursts 

 and the spores are scattered, the affected needles, parts of 

 which are still green, wilting and falling in June and July. 

 The spores which are disseminated in May, when the 

 young shoots of the spruce are forming, can then infect 



them and continue 

 i ^ the disease. 



I. Subjects of Attack, 

 and Distribution. 



The fungus attacks 

 only yearling needles, 

 usually those on the 

 lower branches, and 

 rarely near the top of 

 the tree. 



Spruce is most sub- 

 ject to this disease 

 when from 10 to 40 

 years old. In damp, 

 dense, 10 to 20 years 

 old thickets, the fun- 

 gus is most common, 



Fig. 225. Spruce needles attacked by Chrytior.iyxa 

 ^dbietis, Ung. (Somewhat enlarged.) 



a & b First appearance of disease in the form of 



pale-yellowish marks on needles. 

 c Needle with reddish-brown longitudinal blisters 



(end of March and beginning of April). 

 d Needle with fully formed orange-yellow cushion 



(May). 



but the nature of the 



soil does not appear to have any influence on it. It is met 

 with up to altitudes of 5,000 feet, and is most frequent on 

 south and south-west aspects, or in valleys exposed to the 

 south, whilst damp weather favours its spread, wherever spruce 

 is extensively grown. 



The damage done consists chiefly in loss of increment, and 

 exposure to attacks by bark-beetles, but the trees are not 

 often directly killed by it. Spruce trees are not usually 

 sufficiently advanced in growth to become infected when the 

 spores ripen, and thus frequently escape. 



The disease occurs in Germany Denmark, and Sweden. 



