DISEASES OF CULTIVATED PLANTS 383 
CARROT 
Leaf-Spot. This spotting of carrot leaves is usually caused by the same 
fungus (Cercospora Apii Fres.) as the celery leaf-spot. Upon the carrot the 
trouble is not usually serious. 
CEDAR 
Cedar Apples or Cedar Rust. During the showers of April, May or Juue, 
large or small, jelly-like masses, often one amok or more across, with firmer 
wood-like centers, are frequent upon 
red cedar trees and upon similar 
related plants. Microscopic exam- 
inations of these jelly masses show 
that they contain the spores of arust 
fungus (Gymnosporangium macro- 
pus Lk. and other species of Gym- 
nosporangium). This fact need not 
startle us but for another, namely, 
that this is the completed or teleu- 
tospore stage of a rust which may 
seriously injure the leaves of the 
apple. The apple grower will run 
some risk then, in having about him 
diseased cedar trees. The remedy 
lies in the destruction of the cedar 
trees. 
CATALPA 
Leaf Blight. Leaf blight of 
catalpa has recently been trouble- 
some to growers and puzzling to the 
Pathologist at times. The sudden 
blackening and dying of the leaves 
in early summer has beén traced to 
frost, but other times in later sum- 
mer to root-rot, which see. Fre- 
quently we have found a leaf blight 
fungus (Alternaria sp.) which devel- . 
oped freely upon the spotting leaves - — Sea 
and appeared to be responsible in Fig. 37. Cedar apples caused by rust fungus. 
conjuction with some other rather In May these dry looking apples send out jelly-like 
unfavorable conditions for theyoung _ branches filled with spores of the rustfungus. These 
trees. This will probably give more spores may attack leaves and fruit of apple, as well as 
crataegus and juneberry, (From a photograph by 
trouble in the culture of the catalpa wy. p. Beeching). ; 
than the leaf-spot or mildew which 
have been known much longer and prove less serious. Early applications of 
Bordeaux mixture repeated at moderate intervals should check the disease. * 
Leaf-Spot. The leaf-spot (Phyllosticta Catalpae BE. & M.) is quite frequent upon 
the leaves of catalpa. It rarely causes more than occasional spots in the leaves, 
the injury being inno way comparable to that caused by the catalpa midge. 
Fungicides should be effective against the true leaf-spot. 
Mildew. The leaves of catalpa are often covered over by the powdery 
mildew fungi (Microsphaera elevata Burr., Phyllactinia suffulta Reb.). These 
mildews tend to become conspicuous by the white covering upon the leaves in 
later summer. While unsightly the injuries are rarely serious. 
