470 DISEASES OF CULTIVATED PLANTS 



Olive leaf blotch (Cycloconium oleaginum, Castag.) forms 

 small, roundish blotches of a greyish or yellowish colour, 

 bordered with dark brown on the leaves of the olive, only 

 visible on the upper surface. The spots appear for the most 

 part in the autumn on the leaves of the year ; young leaves 

 are not attacked. The spots grow slowly and are at first 

 altogether black, due to the spores of the fungus, which 

 gradually disappear from the centre as the spot increases in 

 size. The mycelium is almost superficial, it travels along 

 the substance of the upper walls of the epidermal cells, 

 which are very thick, and does not penetrate the parenchyma 

 of the leaf. The mycelium ruptures the cuticle and comes 

 to the surface to produce the spores. 



The conidiophores are very short and bear a single spore 

 at the summit, or in some instances 4-5 spores are pro- 

 duced at the apex. The spores are yellowish-green, usually 

 i-septate, straight or slightly curved, rounded at the base, 

 apex narrowed, 17-25X11 /^. 



It is stated that half strength Bordeaux mixture checks 

 the disease. Trees that were sprayed four times, in July, 

 September, October, and November, retained their leaves 

 intact, whereas unsprayed control trees suffered much from 

 the fungus. 



Prillieux, Malad. des Plantes Agric., 2, p. 362 (1897). 



Boyer, Recher. sur Its Maladies de I' Olivier, Le Cycloconium 

 oleaginum. Montpellier, 1891. 



CLADOSPORJUM (LINK.) 



Hyphae branched, coloured ; conidia elliptical, typically 

 i-septate, rarely 2-3-septate, coloured. 



Tomato leaf rust. This disease apparently originated in 

 the new world, where it proves a dangerous enemy to 

 tomatoes, and at the present day it is equally destructive in 

 Europe, more especially when the plants are forced. It is 

 rarely recorded as occurring on plants grown in the open. 

 The foliage is the part most frequently attacked, the injury 

 first appearing under the form of small spots, which gradually 

 increase in size until very frequently the entire under surface 

 of the leaf becomes covered with a dense, short, browish felt. 

 Diseased leaves soon wilt, change to a dark brown colour, 

 and die. Discoloured stripes or patches often appear on the 



