Bulletin 208, Cucumber Diseases in Florida


maldehyde or steam. If this cannot be done it would be necessary
to use new soil in the benches. Spraying or dusting will have
very little effect on the disease, but considerable benefit is derived
from field applications as preventive.

 POWDERY MILDEW
 Powdery mildew, caused by Erysiphe cichoracearum D. C., ap-
pears upon the leaves of the host plant in all sections of the state,
but its severity depends upon the time of year the plants are
grown. It is much worse during late spring and summer than at
any other times of the year. It is widespread in the United
States and occasionally does considerable damage, although in
Florida it is of very little importance, since the cucumber crop is
produced before June 1. Some trouble has been noted in the
greenhouses in the state.
 The disease is found on all members of the cucumber family
and is severe on squashes. Spores of the fungus are produced in
abundance on the leaves, mostly on the upper surface and are
easily scattered when the leaves are moved. They are carried
considerable distances by the wind and rain. The fungus lives
on wild plants along the fences, woods and roadsides during the
period cucumbers are not growing.


Fig. 26. Cucumber plants severely infected with powdery mildew.