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93 Fungicides for Control of Rhizoctonia on Potted Ornamentals
A. R. Chasecene
University of Florida, IFAS,
Central Florida Research and Education Center Apopk rp 3 0 1994
CFREC-Apopka Research Report, RH-93-7
.,Summ y -,st of Florida
Fungicides such as the thiophanate methyl compounds (Cleary, Domain; Fungo, Topsin
M and Zyban [thiophanate methyl and mancozeb]) provide excellent control of Rhizoctonia
diseases on a wide variety of potted ornamentals. Terraclor and Terraguard have been found
to work very well on some plants but to a lesser degree on others whether symptoms involved
roots, stems or leaves of plants. Chipco 26019 also gave excellent disease control which was
a little better on aerial diseases than stem and root diseases. Comparisons of these fungicides
to Benlate indicate that on many plants affected by Rhizoctonia spp. a number of highly effective
alternatives are available.
Fungicides continue to be an integral part of preventative control of Rhizoctonia diseases
on many ornamental crops. Although Rhizoctonia spp. are soilborne fungi, they do not always
cause root diseases. Aerial blight caused by R. solani is the most common symptom on Boston
fern, while stem rot is the most common symptom on impatiens and poinsettias. This makes
the application site for the fungicides critical since soil drenches are more effective in controlling
root diseases and foliar sprays are more effective in controlling stem rots and aerial blights.
A review of the literature of ornamental potted crops reveals a wide variety of fungicides
which are effective against Rhizoctonia spp. In general, the root and basal stem diseases are
better controlled when the fungicide is applied to the soil as can be seen with the Rhizoctonia
crown or stem rot on poinsettia (Benson, 1991 and Powell, 1988). In this case, a Terraclor
drench was very effective while the same compound applied as a spray was significantly less
effective. A similar situation developed when Benlate was used to control aerial blight of Boston
fern (Chase, 1988). When this compound is used as a spray, excellent disease control occurs
but when used as a drench, disease control is reduced. Best control of impatiens crown (stem)
rot was achieved with drenches of a number of fungicides including thiophanate methyl
compounds (Domain, Fungo and Topsin M) as well as Benlate, Chipco 26019 and Terraclor
(Castillo and Peterson, 1990; Chase and Mellich, 1992 and Chase, 1993). Binucleate
Rhizoctonias are the cause of aerial blight on pittosporum and azalea. The aerial blight on
pittosporum was best controlled with either a Benlate or Domain spray while Terraneb gave no
control (Chase and Stamps, 1992). Terraneb did give excellent control of aerial blight on
'Professor of Plant Pathology, University of Florida, Central Florida Research and Education
Center Apopka, 2807 Binion Rd., Apopka, FL 32703.
Boston fern which is caused by R. solani. Control of the binucleate Rhizoctonia on azalea was
excellent with Chipco 26019 drenches in some tests and only good in others (Frisina, 1988).
Variable results from one trial to the next can be common since environmental conditions cannot
be completely controlled. Table 1 summarizes the literature review of fungicides for
Rhizoctonia control on ornamentals.
Many of the fungicides were tested on a variety of ornamentals. In most tests with
thiophanate methyl compounds (Cleary, Domain, Fungo, Topsin M and Zyban [thiophanate
methyl and mancozeb]) excellent disease control was achieved. Results were usually as good
as those achieved when Benlate was used. Terraclor and Terraguard have been found to work
very well on some plants but to a lesser degree on others whether symptoms were of an aerial
or basal type. Most trials with Chipco 26019 showed a similar pattern with perhaps more
control of aerial diseases than basal stem and root diseases.
Comparisons of these fungicides to Benlate indicate that on many plants affected by
Rhizoctonia spp. a number of highly effective alternatives are available. Be sure to read labels
to check for legal uses and perform phytotoxicity trials on a small group of plants when you are
trying a new fungicide.
Benson, D. M. 1991. Control of Rhizoctonia stem rot of poinsettia during propagation with
fungicides that prevent colonization of rooting cubes by Rhizoctonia solani. Plant
Castillo, S. and J. L. Peterson. 1990. Cause and control of crown rot of New Guinea
Impatiens. Plant Disease 74:77-79.
Chase, A. R. 1988. Boston Fern (Nephrolepis exaltata cv. Compacta) aerial blight of
Rhizoctonia solani AG4. Fungicide & Nematicide Tests 43:288-289.
Chase A. R. 1988. New fungicides or fungicide uses for foliage plants 1988. Proceedings
of the 4th Conference on Insect and Disease Management on Ornamentals. Society of
American Florists. pp. 148-152.
Chase, A. R. 1988. Fungicides for control of leaf spots of foliage plants 1988. Central
Florida Research and Education Center, Univ. of Fl., CFREC-Apopka Research Report
Chase, A. R. 1989. Fungicide trials for Cylindrocladium, Helminthosporium, Pythium and
Rhizoctonia diseases of ornamentals 1989. Central Florida Research and Education
Center Univ. of Fl., CFREC-Apopka Research Report RH-89-15.
Chase, A. R. 1990. 1990 fungicide trials for control of Alteraria, Helminthosporium,
Phytophthora and Rhizoctonia diseases of ornamentals. Central Florida Research and
Education Center, Univ. of Fl., CFREC-Apopka Research Report RH-90-25.
Chase, A. R. 1993. Fungicides to replace Benlate for some diseases of ornamentals. Central
Florida Research and Education Center, Univ. of Fl., CFREC-Apopka Research Report,
Chase, A. R. and T. A. Mellich. 1992. Controlling Rhizoctonia diseases on ornamentals with
fungicides. Central Florida Research and Education Center, Univ. of Fl., CFREC-
Apopka Research Report, RH-92-8.
Chase, A. R. and R. H. Stamps. 1992. Fungicides for control of Rhizoctonia aerial blight.
Cut Foliage Grower 7(11/12):1-3.
Frisina, T. A. and D. M. Benson. 1988. Sensitivity of binucleate Rhizoctonia spp. and R.
solani to selected fungicides in vitro and on azalea under greenhouse conditions. Plant
Powell, C. C., Jr. 1988. The safety and efficacy of fungicides for use in Rhizoctonia crown
rot control of directly potted unrooted poinsettia cuttings. Plant Disease 72:693-695.
Stephens, C. T. and T. C. Stebbins. 1985. Control of damping-off pathogens in soilless
container media. Plant Disease 69:494-496.
Regardless of the pesticide or mixture of pesticides used, it is strongly
recommended that the effects be evaluated on a few plants, under your particular conditions
before treating all plants.
Mention of a commercial or proprietary product or a pesticide in this paper does
not constitute a recommendation by the author, nor does it imply registration under FIFRA
Fungicides for control of Rhizoctonia spp. on some ornamentals.
Excellent Some Poor
Plant Disease control control control
Brassaia Rhizoctonia Banrot drench
(schefflera) root rot
Catharanthus Rhizoctonia Benlate drench Terraclor drench
(Vinca) stem rot Terraguard drench
Epipremnum Rhizoctonia Terraclor drench Cleary drench
(pothos) petiole rot Terraguard drench Domain drench
Zyban drench Fungo drench
Euphorbia Rhizoctonia Terraclor drench Terraclor spray
(poinsettia) crown or stem Benlate drench Chipco 26019
Hedera Rhizoctonia leaf Fungo spray
(English ivy) spot Ornalin spray
Impatiens Rhizoctonia Benlate drench Terraclor spray Terraguard spray
stem rot Chipco 26019 Terraguard spray
Topsin M drench
Liatris Rhizoctonia Terraguard drench Terraclor drench
Nephrolepis Rhizoctonia Benlate spray Benlate drench
(Boston fern) aerial blight Captan spray Chipco 26019
Carbamate spray spray
Daconil spray Manzate spray
Domain spray Terraclor spray
Fungo spray Terraguard spray
Pittosporum Rhizoctonia Benlate spray Terraneb spray
aerial blight Domain spray
Radermachera Rhizoctonia Domain spray Terraclor spray
(China doll) damping-off Terraclor drench Terraguard spray
Topsin M spray
Rhododendron Rhizoctonia Chipco 26019 Benlate spray or
(azalea) aerial blight drench drench
Spathiphyllum Rhizoctonia Terraguard drench Terraclor drench