JOURNAL 



OF THE 



Royal Horticultural Society. 



Vol. XXIX. 1905. 

 Part IV. 



FUNGOID PESTS OF FOREST TREES. 



By M. C. Cooke, M.A., LL.D., V.M.H., A.L.S. 



"We have illustrated some of the most prominent pests of forest trees, 

 but they are very numerous, and not of so much interest to horticulturists 

 as other sections ; hence we have not considered it incumbent upon us to 

 enumerate other than those which are most likely to present themselves 

 under ordinary circumstances. Those persons who are specially interested 

 in forestry will not find our list by any means exhaustive, but simply 

 suggestive, except in so far as regards the trees which surround, or are 

 included in, large gardens and shrubberies. 



Ochry Maple Spot. 

 Phyllosticta aceris (Sacc), PI. XIX. fig. 1. 



The ordinary leaf- spots are not any considerable damage to forest 

 trees, unless they are unusually plentiful ; in any case they must be 

 regarded as diseases. The common Maple is very subject to one which 

 forms nearly circular bleached ochraceous spots on the leaves, over which 

 are scattered the dot-like receptacles immersed in the tissues. The 

 sporules, which are contained within these receptacles, are ovoid, and 

 rather small (5x3^) with two guttules, which are extruded from the 

 receptacles through a minute orifice when mature. 



The above species was first recorded for Italy, and in no other 

 country except Britain. 



It is almost impossible to suggest any remedy for these leaf-spots, 

 since spraying is out of the question with objects of this size, although it 

 may be adopted whilst the trees still remain as seedlings. 



Sacc. Syll. iii. 61 ; Grevillea, xiv. 71. 



Quite twenty other species of leaf-spot, caused by Phyllosticta and 

 Septoria, have been recorded in different parts of the world on leaves of 

 Acer. 



