Fungicides for Rhizoctonia Control on Ornamentals - 1993 Results

A. R. Chase,
Professor of Plant Pathology,
University of Florida, IFAS,
Central Florida Research and Education Center - Apopka,
2807 Binion Rd., Apopka, FL 32703.
CFREC-Apopka Research Report, RH-93-14

Fungicides continue to be an important part of ornamental plant production. Preventative control of Rhizoctonia diseases frequently relies on use of fungicides on many ornamental crops. Rhizoctonia spp. are soilborne fungi that commonly cause aerial blight and stem rot. The fact that the pathogen occurs in the potting medium but causes above ground diseases makes the application site for a fungicide critical. Soil drenches are more effective against diseases of roots while foliar sprays are generally more effective against aerial blights and stem rots. The following table summarizes results of fungicide tests for control of Rhizoctonia diseases of ornamentals conducted in 1993.

Many of the fungicides were tested on a variety of ornamentals. In most tests with thiophanate methyl compounds (Domain, Cleary and Topsin M), good to excellent disease control was achieved. PCNB (Terraclor) and triflumizole (Terraguard) have been found to give excellent control on some plants (vinca and spathiphyllum) but only good control on others (pothos and impatiens). Iprodione (Chipco 26019) gave excellent control of Rhizoctonia stem rot on vinca when used as a drench and Rhizoctonia stem rot on impatiens when used as a spray. Both maneb (Maneb) and mancozeb (Penncozeb) gave good control of Rhizoctonia diseases of pothos and English ivy with excellent control on Boston fern. The experimental compound from Ciba (CGA-17506) gave excellent control of Rhizoctonia diseases on vinca and impatiens.

Comparisons of these results to those of previous years indicate that on many ornamentals a large number of highly effective alternatives continue to be available for Rhizoctonia control. Be sure to read labels, check for legal uses and remember to spray fungicides when the disease affects leaves and stems and drench them when the disease affects roots.


Table 1. Fungicides for control of Rhizoctonia spp. on some ornamentals.
Plant Disease Excellent control Some control
Catharanthus
(Vinca)
Rhizoctonia
stem rot
CGA-17506 drench
Chipco 26019 drench
Terraclor drench
Terraguard drench
 
Epipremnum
(pothos)
Rhizoctonia
petiole rot
   Topsin M drench
Cleary drench
Maneb drench
Penncozeb drench
Hedera
(English ivy)
Rhizoctonia
leaf spot
Benlate spray  Topsin M spray
Cleary spray
Penncozeb spray
Maneb spray
Impatiens Rhizoctonia
stem rot
CGA-17506 drench
Terraclor drench
Chipco 26019 drench
Terraclor drench
Terraguard drench
Nephrolepis
(Boston fern)
Rhizoctonia
aerial blight
Cleary spray
Topsin M spray
Penncozeb spray
Maneb spray
 
Pittosporum Rhizoctonia
aerial blight
Domain spray Terraguard spray
Spathiphyllum Rhizoctonia
petiole rot
Terraclor spray
Terraguard spray
 

Pesticides should be applied according to label directions.

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 in this paper
does not constitute a recommendation by the authors,
nor does it imply registration under FIFRA as amended.

Reference to University of Florida/IFAS Pest Control Guides