Diseases of Plants 299 
leaves, the plants may in a short time become almost 
leafless. In such a condition the plants will produce 
few or no fruits. 
In the center of the discolored spots, small dark dots 
or pustules may be found. These are cistern-like cavities 
in which countless spores are produced. Around the 
spores is a material which when wet becomes jelly-like 
and swells, pushing the spores in sticky clusters out of the 
opening of the case. They will cling to insects and to 
the hands of the gardener, and thus become distributed. 
Rain may splash spores from leaf to leaf and from plant 
to plant. Spores which fall to the ground will withstand 
severe drying for at least three days, during which time 
they may be blown about with the dust. Many gar- 
deners quite naturally make the mistake of thinking 
that the disease is caused by wet weather, but the wet 
weather simply favors the spread of the parasite. 
Control of this disease is effected largely by preven- 
tive measures. Clean soil should be used in flats and 
cold frames in which seedlings are started. The spores 
live over winter on stems and leaves of old plants; hence 
the dead remains of all tomato plants should be burned in 
autumn. The spread of the disease can be checked by 
spraying with Bordeaux mixture (4-4-50 formula) at 
intervals of about 1o days, or more often during rainy 
weather. At the first signs of this disease the gardener 
should tie up plants to stakes, remove and burn the lower 
and infected leaves which are wilting and showing 
blotches, and then spray with Bordeaux mixture. All 
this work, as well as that of cultivation, should be done 
when the plants are dry. 
