DISEASES OF THE PEAK TREE ] 239 



The disease develops as small yellow dots early in 

 autumn, which increase in size and become reddish 

 and then brown, and in the centre become ashy grey 

 and develop many minute black points. The same 

 disease attacks the leaf-stalks in the shape of black 

 points surrounded by a reddish border, which coalesce 

 and envelop the leaf-stalk causing it first to thicken 

 and then to become fissured transversely. Brown spots 

 rather large but irregular in shape are sometimes 

 formed on the upper surface of the leaf by Ascochyta 

 pirina Pegl., the central part of these spots soon 

 becoming ashy grey, and afterwards become crowded 

 with minute black dots. The same disease has been 

 noted in rare instances also on the green fruit. 



The pear- mildew (male bianco] is a rare disease on 

 our pear trees, and is caused by Phyllactinia suffulta 

 Sacc. The young twigs and foliage affected by this 

 disease assume a powdery aspect, with microscopic black 

 spots or nodules. 



Gymno sporangium Sabinae Wtr. attacks the leaves 

 and sometimes also the fruit of the pear tree in France 

 and Italy, but this disease has not been detected in 

 these Islands. It may be remarked that the mature 

 form of this fungus, Roestelia cancellata Rebent, lives 

 on junipers, which with the exception of rare individuals 

 of funiperus virginiana, do not exist here. Another 

 fungus, Diplodia Pseudodiplodia Fuck, lives on dead 

 twigs of the pear, but its nature seems to be entirely 

 saprophytic. 



Polyporus ignarius Fr., P. squamosus Fr. P., 

 sulphur ens Fr. and P. cinnamomeus Trag. have been 

 found growing on the stem of the pear in F ranee 

 and Italy. Of these only the last, P. cinnamomeus, has 

 been found growing on the old stems of the pear in 

 the Boschetto. Should it become frequent the same 

 treatment may be adopted as suggested against Poly- 

 porus obliquus of Citrus trees. 



