238 [ DISEASES OF THE PEAR TREE 



dots with coalescing whitish margins. Fusicladium 

 pirinum is considered by Aderhold as the conidial form 

 of Venturia pirina Cooke, whose perithecia are formed 

 in autumn on the diseased leaves and also on the twigs. 

 A bad attack of this fungus in moist summers may result 

 in the destruction of 50 per cent, of the crop, certain pears 

 like Angelica of Malta growing in shaded situations 

 being very liable to it, while others such as Duchesse 

 de Berry d'ete and Beurr6 superfin being liable to the 

 minutely dotted form above alluded to. As a remedy 

 against these diseases it is recommended to collect and 

 burn all diseased twigs, leaves and fruits, and to spray the 

 trees repeatedly with a i per cent, solution of Bordeaux 

 mixture. 



On the leaves of the pear during the autumn months 

 are sometimes developed small whitish round spots 

 surrounded by a brown or reddish margin. These spots 

 are due to the presence of the fungus Sphaerella sentina 

 Fckl; other spots discoidal in shape, with or without 

 a brown margin, are produced by Phyllosticta piricola 

 Sacc. Ph. pirina Sacc. is an allied species also common 

 on our pear trees, and hardly distinguishable from the first 

 except by the use of the microscope. Large irregular 

 brown spots on the upper surface of the leaf made 

 up of black lines crossing each other in all directions 

 are due to Asteroma geographicum Desm.; and large 

 brown spots, also on the upper surface, with a radiating 

 black margin, are due to Vermicularia trichella Tr. 

 Another fungus Stigmatea Mespili Sor, which also attacks 

 the quince and the medlar, causes small spots which 

 penetrate the tissues of the leaf and are visible on 

 both surfaces. At first these spots are reddish and 

 then become brown with a small round' crust in the 

 centre. The leaves affected by this fungus soon become 

 brown and drop off. 



Gleosporimn 'pirinum Pegl. is another fungus fre- 

 quently attacking the leaves of the pear in our orchards. 



