| Material Information
||Chemical control of Myrothecium crown rot and leaf spot of Rex begonia
||ARC-A research report
||3 p. : ; 28 cm.
||Chase, A. R ( Ann Renee )
Agricultural Research Center (Apopka, Fla.)
||University of Florida, IFAS, Agricultural Research Center-Apopka
||Place of Publication:
||Begonia rex -- Diseases and pests -- Control -- Florida ( lcsh )
Myrothecium -- Control -- Florida ( lcsh )
Leaf spots -- Control -- Florida ( lcsh )
||government publication (state, provincial, terriorial, dependent) ( marcgt )
bibliography ( marcgt )
non-fiction ( marcgt )
||Includes bibliographical references (p. 3).
||Statement of Responsibility:
||Florida Historical Agriculture and Rural Life
|Table of Contents
The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
site maintained by the Florida
Cooperative Extension Service.
Copyright 2005, Board of Trustees, University
CHEMICAL CONTROL OF MYROTHECIUM CROWN ROT
AND LEAF SPOT OF REX BEGONIA
A. R. Chase
University of Florida, IFAS .
Agricultural Research Center ApopkJ i
ARC-A Research Report RH-82-10
Myrothecium crown rot and leaf spot is a serious disease ofTmany.--. 'j
ornamental plants including gloxinia (2), aphelandra (1), dieffenbachia,
begonia, aglaonema, and lipstick vine. Symptoms are usually found on
leaves and appear as dark brown to black somewhat circular lesions which
can be wet or dry. The lower side of lesions contain black fruiting
bodies of the pathogen surrounded by a white fringe. They are easily
visible to the naked eye and are diagnostic for this disease. Leaf
spots of gloxinia and begonia may occur but the most serious symptom is
the crown rot which stops plant growth (begonia) or girdles the stem
when plants near maturity (gloxinia). The purpose of this research
was to identify the optimum chemical control for Myrothecium crown rot
and leaf spot of begonia.
Begonias were obtained from tissue culture and planted in 4" pots
in a medium containing Canadian peat, cypress shavings, and pine bark
(2:1:1 by volume) which was amended with 4.4 kg Osmocote (19:6:12), 4.2
kg dolomite, and 0.9 kg Micromax (micronutrient source) per m3 of medium.
After one week the plants became naturally infected with Myrothecium
roridum and benomyl (2.3 g/gal) was applied as a drench to all pots.
No control was achieved and the same plants were then employed in the
All plants were artificially inoculated with spores of M. roridum.
After one week chemical sprays (Table 1) were initiated and continued
on a weekly interval for a total of eight applications. Fungicides
were applied at the recommended rates to foliage and plant crowns with
the exception of CGA 64250 which was used as a soil drench applied at
the rate of 40 ml per pot twice at monthly intervals. Fifteen plants
were used in each treatment. Plants were evaluated for quality by
counting the number of healthy leaves after five applications and the
percentage of high quality plants at the end of the experiment.
All of the fungicides were safe for use on Rex Begonia except the
CGA 64250. This chemical caused leaf deformity, severe stunting and
burning. In another test, a similar reaction was noted when gloxinias
were drenched with this compound. The best plants were produced when
either Daconil or Manzate were used. The number of healthy leaves and
percentage of high quality plants at the end of the test support the
superiority of these compounds compared to the others used (Table 1).
Past research involving the control of this disease on gloxinia (3)
indicated that Rovral at 3.8 g/gal was effective and safe. Since their
tests did not include either Daconil or Manzate a comparison cannot be
made. Use of Daconil or Manzate at the recommended rates on a weekly
interval provided good, safe control of Myrothecium crown rot and leaf
spot of Rex Begonia in this test.
Use of trade names in this report implies no endorsement of specific
pesticides but were used only as a means of identification.
Table 1. Influence of chemical treatments on control of Myrothecium
crown rot and leaf spot of Rex Begonia.
Mean no. healthy
Treatment Rate leaves/plant Percentage high quality
Benlate 50WP 2.3 g/gal 3.7 ay 27
Manzate 75WP 6.8 g/gal 5.6 b 53
Ornalin 50WP 2.3 g/gal 3.5 a 7
Rovral 50WP 2.3 g/gal 3.6 a 27
CGA 64250 1.0 ml/gal 5.5 b 33
Daconil 75WP 6.8 g/gal 6.3 b 67
Zyban 75WP 6.8 g/gal 5.1 ab 33
Water --- 3.5 a 7
ZFungicides were applied weekly for eight weeks.
YNumbers followed by the same letter in the same column were not
statistically significant at the 5% level using Duncan's multiple
1. Chase, A. R. 1981. Comparison of Myrothecium sp. and Corynespora
cassiicola leaf spots on two cultivars of Aphelandra squarrosa Neese.
Proc. Fla. State Hort. Soc. 94:(in press).
2. Littrell, R. H. 1965. A Myrothecium rot of gloxinias. Plant Dis.
3. Ploetz, R. C. and A. W. Englehard. 1980. Chemical control of
Myrothecium disease of Gloxinia. Proc. Fla. State Hort. Soc. 93:181-183.