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Copyright 2005, Board of Trustees, University
;" /. i? : 2: SIC i
9D -/-P 301W
93 -6/ DISEASES OF LEATHERLEAF FERN AND THEIR CONTROL '
A. R. Chase1 :!::ersitY of Florida
Central Florida Research and Education Center Research Report, RH-93-18
Leatherleaf fern (Rumohra adiantiformis) is grown for the cut foliage markets in Europe,
the United States and Canada. The majority of the fern production remains located in central
Florida although offshore production has increased dramatically during the past ten years. Warm,
moist weather promotes production of the fern, but also favors development of several diseases of
leatherleaf fern. Despite the favorable environment, relatively few diseases are common or
economically important on this crop grown in Florida.
Anthracnose or Colletotrichum Blight (Figure 1)
Anthracnose has been a problem in Costa Rica for the past few years but was not reported
in Florida until early this summer. The disease affects newly emerging fronds most severely by
causing them to become blackened preventing development. Older fronds (mature) do not appear
to be easily infected. In some nurseries the affected beds look as though a blow torch has been
used on them. Fungicides which may work on this disease include Chipco 26019, Cleary's 3336,
Daconil 2787, Dithane F-45, Dithane M-45, Domain, Fore, Systec and Thalonil (1). Follow labels
for rates and intervals of use. Growers should be very careful not to bring in cut fern from the
tropics or Florida growers with this disease.
Cylindrocladium Leaf Spot (Figure 2)
Spots are pinpoint to 1/2 inch long and are reddish to grayish brown. They can be water-
soaked and coalesce to encompass much of the frond. Disease is most severe in the summer but
can occur during warm winters. The fungicides listed for anthracnose are labeled on this fern and
can aid in control of Cylindrocladium leaf spot. Irrigation early in the day allows rapid drying of
the foliage and can reduce disease spread.
Pythium Root Rot (Figure 3)
Plants are grayish-green or chlorotic in color and may wilt. Roots are brown, mushy and
reduced (stunted). Disease is rarely severe unless the fernery has poor drainage and excessive
winter rains or applications of water for freeze protection are common. Aliette, Banrot, Banol, and
Subdue are labeled for this disease on leatherleaf fern. Provide good drainage to avoid
development of Pythium root rot.
Rhizoctonia Aerial Blight (Figure 4)
Spots occur all over the plants and are dark-brown to grayish, sometimes covering entire
fronds. The web-like mycelium of the pathogen frequently spreads up the stipes onto the fronds
especially in the center of the plants where the moisture levels are high. Disease is most common
in the summer. The fungicides mentioned for anthracnose should aid in control of Rhizoctonia
aerial blight. Keep fern cut to allow good air circulation and reduce disease development. Many
1Professor of Plant Pathology, University of Florida, IFAS, Central Florida Research
and Education Center Apopka, 2807 Binion Rd., Apopka, FL 32703.
other cut foliage crops are hosts of Rhizoctonia spp. and disease can readily spread from one crop
Figure 1. Anthracnose or
Colletotrichum blight Figure 2. Cylindrocladium leaf spot
Figure 3. Pythium root rot (plant on right)
Figure 4. Rhizoctonia aerial blight
1. Stamps, R. H., R. A. Dunn, A. G. Hornsby, D. E. Short, and G. W. Simone. 1993.
Pesticides labeled for use in commercial leatherleaf fern production in Florida 1993. Cut
Foliage Research Note, CFREC-Apopka, RH-93-B.