PESTS OF GARDEN VEGETABLES. 



807 



Horseradish Leaf Spot. 

 Phyllosticta Armoracice (Cooke), PI. VII. fig. 103. 



A number of specimens of this parasite were collected in a garden, fully 

 a quarter of a century ago, and distributed, under the name of Septoria 

 Armoracice, when the distinctions between Septoria wad. Phyllosticta were 

 not recognised. The spots and their disposal upon the leaves appear to 

 be precisely the same as in Septoria. 



The receptacles, or perithecia, are minute and immersed in the spots. 

 The sporules are small, oblong, and colourless (6 x 3-4 /u), and are 

 produced in great quantity. 



It is uncertain where else this species has been obtained, as we know 

 of no record beyond the specimens above named. 



The external appearance of the affected leaves is the same in the 

 three species of Phyllosticta, Ascochyta, and Bamularia, as visible to the 

 naked eye. 



Cooke, Fun. Ex. 32. 



Horseradish Leaf Spot. 

 Ascochyta Armoracice (Fckl.), PI. VII. fig. 104. 



As already stated, the leaf spots caused by this disease can scarcely 

 be distinguished from those caused by the Bamularia, except possibly in 

 the recognition of the minute dot-like receptacles which are seated upon 

 the spots. 



The sporules, which are produced within the receptacles, are oblong, 

 obtuse at the ends, and divided transversely into two cells (18-20 x3ju), 

 which is the only apparent distinction between Ascochyta and Phyllo- 

 sticta. 



This cannot be considered a dangerous or troublesome garden pest, 

 but if its banishment is desired, it would be well to try spraying with one 

 of the copper solutions. 



The fungus is known in the Rhine Provinces, Holland, and Italy. 



Sacc. Syll. iii. 294 ; Fckl. Sym. Myc. 388. 



Horseradish Spot Mould. 

 Bamularia Armoracice (Fckl.), PI. VII. fig. 105. 



This little white mould is common enough on leaves of Horseradish ; 

 although it probably does no harm to the roots, still it makes the foliage 

 look shabby enough. 



The spots are at first ochrey-white, then pallid, and somewhat circular, 

 until they run together into a larger blotch. The fertile threads arise 

 from the buried mycelium in small tufts, and are erect and unbranched. 

 The conidia, or sporules, grow singly at the tips of the threads, and are 

 rod-shaped, sometimes a little thickened at the middle, and obtuse at the 

 ends (20 x 4). 



There is hardly any appearance of mould to the naked eye, or at most 

 only a little mealiness on the spots. Finally many of the decayed spots 

 drop out, leaving holes in the leaves. 



