346 



GREENHOUSE MANAGEMENT. 



borders. The spots (Fig. 120) increase, and running 

 together may destroy the entire leaf. They have a gran- 

 ular appearance caused by clusters of fungus threads 



(B) upon which the septate 

 spores (G) are borne. The 

 disease spreads very rapidly 

 and may become quite trouble- 

 some. If taken in time, the 

 disease may be kept in check 

 by the use of the copper com- 

 pounds. It will be well to 

 remove all diseased portions 

 and spray the plants with Bor- 

 deaux mixture. 



X'$n, -«S3?* LEAF BLIGHTS. 



FIG. 126. LEAF BLIGHT OF MIG- •VT OQT ,l w „H Wlnnfa nvo enh 



nonette. (Cercospora iiesedm.) JNeaiiy an plants are SUD- 



B, Thready c. Spores. (Band ^ t() ^ ^^ Qf certain 



fungi that are known as leaf blights. They belong to 

 several species, but are alike in causing the appearance of 

 yellow spots upon the leaves, which may spread until 

 they assume large proportions, and if they are very 

 numerous the leaves may be destroyed. Generally at 

 the place where the spot first showed, a dark brown dot 

 will later on appear ; this is due to the development of 

 a large number of spores, by which the disease will be 

 scattered. When the spots first show, the leaves attacked 

 should at once be removed and burned. Sometimes, 

 there are but one or two spots upon large leaves, and it 

 will be possible to cut off the portion of the leaf upon 

 which the spot is situated, but to be effectual a consid- 

 erable amount of the leaf should be taken off, as the 

 mycelium of the fungus has probably spread to some 

 distance beyond the margin of the discolored portion. 

 Most of these fungi work within the tissues, and no sur- 

 face application will stop their spread within the leaf, 

 but by applying the Bordeaux mixture, or cupram, we 



