424 DISEASES OF CULTIVATED PLANTS 



Nursery stock more especially often suffers severely from 

 this disease. Duggar, who has devoted considerable attention 

 to the subject, states that three sprayings with Bordeaux 

 mixture give almost perfect protection. The first immediately 

 after the petals fall, and two subsequent sprayings at intervals 

 of two or three weeks. 



Duggar, B. M., Cornell Univ. Agric. Exp. St., U.S.A., 

 Bull. 145 (1898). 



Strawberry leaf blight (Septoria fragariae, Desm.) often 

 causes considerable injury to the foliage of cultivated straw- 

 berries ; it also occurs on wild species of Fragaria and 

 Potentilla. The fungus forms rather large, circular, brownish 

 patches with a red margin. At a later stage the central 

 portion becomes pale coloured, and is studded with numerous 

 minute perithecia, out of which the spores ooze in whitish 

 tendrils. Spores elliptic-oblong, 3-septate, hyaline. 



Saccardo gives this fungus as a form of Sphacrella fragariae 

 (Tul.). 



Treatment same as for strawberry leaf spot, which see. 



Wheat blight. During a cold, backward spring the leaves 

 of autumn-sown wheat are often more or less covered with 

 patches caused by Septoria tritici (Desm.). Such leaves turn 

 yellow and die prematurely. According to Cavara this fungus 

 causes serious injury to the wheat crop in the north of Italy. 

 It also occurs on other cereals. 



The conceptacles are very minute and immersed in the leaf, 

 and form very minute black dots at the surface, due to the 

 mouths of the conceptacles protruding through the epidermis. 

 Conidia filiform, hyaline, 3-5-septate, 50-60X3-5 /*. 



Janczewski considers that certain other very minute con- 

 ceptacles, containing myriads of exceedingly minute, slender, 

 curved, hyaline spermatia, which are often found accompany- 

 ing S. tritici, to belong to that species. These minute bodies 

 he has called Phoma secalinum. 



Very frequently an ascigerous fungus, called Leptosphaeria 

 tritici, is found mixed with Septoria tritici on the leaves of 

 wheat. The perithecium is black, subglobose, with a con- 

 spicuous neck, which usually protrudes through a stoma. 

 The asci are subcylindrical, 8-spored, spores 2-seriate in the 

 ascus, elliptic-oblong, ends narrowed, 3-septate, yellowish. 





