94 Diseases of Greenhouse Crops 



b. Colored areas or spots. 



White or gray^ such as mildews, white 



rusts, etc. 

 Yellow^ many leaf spots. 

 Ked or orange^ rusts, leaf spots. 

 Brown, many leaf spots. 

 Black, black rusts. 

 Variegated, leaf spots, mosaic 



2. Shot hole, perforation of leaves. 



3. Wilting, wilts, damping off. 



4. Necrosis, death of parts such as leaves, twigs, 

 stems, etc. 



5. Atrophy, dwarfing or reduction in size. 



6. Malformations or excrescences, galls, pus- 

 tules, tumors, cankers, rosettes. 



7. Exudation, slime or gum flow. 



8. Rotting, dry or soft rots. 



1. Diseases of a Mechanical Nature 



Greenhouse plants, contrary to those grown out- 

 doors, are open to but few injuries of a mechanical 

 nature, for it is seldom, indeed, that indoor plants 

 are injured by rain, hail, or frost. 



Sunburn. While most greenhouse crops require 

 a great deal of light, a few are injured by it. Some 

 varieties of tomatoes, the Earliana especially, under 

 the influence of strong sunlight are subject to sun- 

 scald. Sunburn may be overcome by shading the 

 glass. Of the various shading materials, the cheap- 

 est and quickest to use is air-slaked lime. The 



