340 VEGETABLE FORCING 
Downy Mildew (FPeronoplasmopara Cubensis (B. & 
C.) Cl.) is a fungous disease that attacks the leaves of cu- 
cumbers. The angular, yellowish spots are followed by the 
yellowing of the entire leaf and, if the infection is severe, 
the death of the plant may occur. The cucumbers on dis- 
eased plants are small and inferior in quality. Under 
favorable conditions the disease develops and spreads to 
other plants with marvelous rapidity. It is one of the most 
destructive enemies of greenhouse cucumbers. Insufficient 
light and sunshine, high temperatures and high humidity 
are the conditions which are most favorable to the rapid 
development and dissemination of this fungous trouble. 
Spraying with bordeaux mixture is valuable, but sanitary 
measures and the proper regulation of cultural conditions 
are most important. 
Powdery Mildew (Erysiphe Cichoracearum, D. C.) is 
often destructive to greenhouse cucumbers when conditions 
of heat, light and moisture are favorable to the progress of 
the disease. This disease makes its appearance on the upper 
surface of the leaves, where the fungus produces a super- 
ficial growth which is powdery white in appearance. Severe 
attacks cause the plants to become sickly and finally to die. 
Bordeaux mixture, applied promptly and thoroughly, is 
valuable in checking the ravages of this disease. 
A bacterial wilt (Bacillus tracheiphilus, Smith) is often 
found on greenhouse cucumbers. Most entomologists 
believe that the disease is transmitted by the cucumber 
beetle and the squash bug. The disease causes the plants 
to wilt as if they were suffering from the lack of water, 
and they finally die. 
Another wilt (Fusarium niveneum, Smith) is also fairly 
common in the greenhouse. It is a fungus which works 
internally in the stem of the plant and finally closes water 
vessels, thus interfering with the functions of the stem, 
causing the plant to wilt and die. This disease is also trans- 
mitted by the cucumber beetle and squash bug, and war 
