SCentral Florida Research
SVFLORIDTA and Education Center
Institute of Food and Agricultural Sciences Research Report
1993 Fungicide Trials for Control of Some Diseases on Ornamentals
A. R. Chase'
CFREC-Apopka Research Report, RH-93-17 SP 3 0 9l4
pn',ersitY of Flori.
In 1993, a series of fungicide trials for control of diseases on ornamental plants were
completed. All tests were performed within labeled rates for those fungicides with current
labels. Some of the trials concentrated on discovering new uses for compounds currently
registered for some ornamentals (Cleary's 3336, Daconil, and Terraguard) while others involved
compounds registered on other crops (Sentinel, Terraneb and Topsin M). Additional trials were
performed to better determine the range of activity for new experimental compounds such as
fluazinam and myclobutanil. As in previous years the tests were designed to gain the maximum
amount of information which could lead to label expansion and improved availability of
fungicides for the ornamental producer.
The results of 1993 trials are summarized in Table 1. The two tests performed on
azaleas with Cylindrocladium cutting rot showed that both Terraguard (triflumizole from
Uniroyal) and Terraneb (chloroneb from Kincaid Enterprises) gave excellent disease control.
Penncozeb (a mancozeb compound from Atochem) gave some control, but the two thiophanate
methyl compounds (Cleary's 3336-W. A. Cleary and Topsin M Atochem) as well as Daconil
(chlorothalonil from ISK Biotech), did not give any measurable control in these trials.
Fusarium leaf spot was relatively easy to control with Terraguard and combinations of
Terraguard with other foliar fungicides. Powdery mildew on gerber daisy was controlled best
with Penncozeb, Maneb (maneb from Atochem) and fluazinam (ISK Biotech). The thiophanate
methyl compounds (Cleary's 3336 and Topsin M) did not provide a high degree of control in
In a field trial with Cylindrocladium leaf spot on leatherleaf fern, best control was
achieved with applications of Daconil on a ten-day interval. The experimental compound,
'Professor of Plant Pathology, Central Florida Research and Education Center Apopka, 2807
Binion Rd., Apopka, FL 32703.
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fluazinam caused some phytotoxicity to the fern but also gave good disease control.
Helminthosporium leaf spot on maranta was controlled with mancozeb type compounds such as
Fore and RH-0611 (both from Rohm and Haas). In this case, Terraguard gave a lesser but
significant degree of disease control.
Black spot on roses proved difficult to control but both Maneb and Penncozeb gave good
disease control. Topsin M did not give a significant degree of control, although Cleary's 3336
(also thiophanate methyl) resulted in a good degree of black spot control on rose.
Cylindrocladium root and petiole rot has always been very difficult to control. Previous work
has shown that best control is obtained with drenches of Terraguard which remained the case
in this test. In addition, myclobutanil, alone and in combination with mancozeb (RH-0611), also
gave a moderate degree of disease control.
Fungicide tests on diseases of ornamentals continue to show that both labeled and
experimental compounds are available which give at least good control of the most serious
diseases of ornamentals. Care must be taken to follow label instructions if we are to retain use
of these products.
Table 1. Summary of 1993 fungicide trials on miscellaneous disease of ornamentals.
Degree of control for each fungicide
Plant Disease Excellent Some Poor
Azalea Cylindrocladium Terraneb SP Penncozeb Cleary's 3336
cutting rot Terraguard Topsin M
Dracaena Fusarium leaf spot Terraguard
Powdery mildew Penncozeb Topsin M Cleary's 3336
Gerber daisy Maneb Daconil 2787
Cylindrocladium Daconil Fluazinam
Leatherleaf fern leaf spot
Maranta Helminthosporium RH-0611 (mancozeb Terraguard
leaf spot and myclobutanil)
Rose Black spot Penncozeb Topsin M
Spathiphyllum Cylindrocladium Terraguard Myclobutanil Fore FL
root and petiole rot RH-0611