Bulletin 229, Diseases of Citrus in Florida


 DAMPING-OFF
Caused by Rhizoctonia solani Kiihn and Sclerotium rolfsii Sacc.
 Damping-off, a universal trouble of seedling plants, commonly
attacks citrus seedlings. This is primarily a disease of young
seedlings, attacking them at any time after the seeds germinate
until the stem tissues become woody. The first indication of
damping-off usually is a watersoaked or brown area of decaying
tissue on the stem, at or near the surface of the ground (Fig.
46). This lesion extends up the stem and girdles it to a point
about a half-inch above the ground. The soft decayed cortical








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 Fig. 47.-Damping-off of citrus seedlings.
tissue then sloughs off and the exposed woody tissue dries up
and becomes whitened. The seedlings usually are completely
girdled before they wither and die and do not fall over as in
the usual form of damping-off (Fig. 47).
 Damping-off occurs characteristically in spots or patches in
the seedbed. These spots may enlarge considerably if the soil
conditions are favorable for the spread of the causal organism.
A number of different soil-inhabiting fungi have been found
associated with the damping-off of citrus seedlings but Rhizoc-
tonia solani KUihn has been found to be the most common cause
in Florida. Sclerotium rolfsii Sacc. has also been found respon-
sible for the damping-off of citrus seedlings in some cases.