52 



The effect of the fungus filaments within the tissues is to 

 cause the gradual death of the branch. In the case of its 

 ally, the Apple Canker fungus, Nectria galligena (see Leaflet 

 No. 56), the tree resists the parasite, forming a callus, and a, 

 canker- wound is the result. No callus formation takes place 

 in Coral Spot. The mycelium invades the woody portion of 

 the stem and kills and blocks up the water-conducting tissues. 

 It is not surprising, therefore, that in bush fruits such as 

 currants the death of the attacked branches should follow 

 sooner or later. Wood which has been destroyed by the Coral 

 Spot fungus turns first dark green or black and then brown. 

 In the case of apples (as also in trees such .as sycamore and 

 horse chestnut) larger branches may be attacked with equally 

 fatal consequences. Soon after the tissues are killed the fungus 

 commences to form spores, these being borne in amazing 

 quantities on the pink pustules above referred to. These 

 spores are very minute and are termed conidia (conidia meaning 

 dust-like) and are developed all the year round. Another 

 form of spore is, however, also produced, chiefly during spring, 

 and especially on the larger branches. These spores are formed 

 in dark red bodies named perithecia and are usually borne 

 on the site of old conidial pustules. The perithecia are com- 

 parable in function to those so well-known in American Goose- 

 berry Mildew. 



Measures of Control. 1. Prevention. It has been shown 

 that the fungus gains entrance in two ways, viz., through 

 dead branches and through wounds. All dead shoots and 

 branches should therefore be removed during pruning and 

 care taken that no snags which will die back are left. Injury 

 to bushes should also be avoided whether in pruning or in 

 cultivation with the hoe. Wounded surfaces should be 

 protected by tar. 



2. Treatment of Attacked Trees. The disease may often be 

 arrested by the rigorous use of the knife. Diseased branches 

 should be cut clean out, taking care to cut back to healthy 

 wood and to protect the wound. In the case of large boughs, 

 if the attack is dealt with early, it may be possible to save 

 the branch by removing the infected area with a knife or 

 chisel. Great care must be taken to remove all the affected 

 tissue and to tar the wounds. 



3. Sanitation. Accumulations of dead wood and sticks 

 should never be allowed in an orchard. On such debris fungi 

 of all sorts flourish, including those causing Coral Spot, Silver 1 

 Leaf, Canker and other dangerous diseases, and from these 

 fungi millions of spores are liberated into the air and blown 

 amongst the trees. The better the sanitary condition of the 

 orchard, the less the chances of infection by fungus parasites* 



