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 Historic note
 Diseases observed
 Inoculations with verticillium...
 Discussion
 Literature cited














Group Title: Sub-Tropical Experiment Station - mimeographed report ; no. SUB67-1
Title: Diseases of kenaf in Dade County, Florida and their relationship to winter vegatable production
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Permanent Link: http://ufdc.ufl.edu/UF00067793/00001
 Material Information
Title: Diseases of kenaf in Dade County, Florida and their relationship to winter vegatable production
Series Title: Mimeographed report
Physical Description: 3 leaves : ; 28 cm.
Language: English
Creator: Averre, Charles W ( Charles Wilson ), 1932-
Sub-Tropical Experiment Station
Publisher: University of Florida, Sub-Tropical Experiment Station
Place of Publication: Homestead Fla
Publication Date: 1966
 Subjects
Subject: Kenaf -- Diseases and pests -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (leaf 3).
Statement of Responsibility: C.W. Averre.
General Note: "November, 1966."
Funding: Mimeographed report (Sub-Tropical Experiment Station) ;
 Record Information
Bibliographic ID: UF00067793
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 71816624

Table of Contents
    Historic note
        Copyright
    Diseases observed
        Page 1
    Inoculations with verticillium albo-atrum reinke and berth
        Page 2
    Discussion
        Page 2
    Literature cited
        Page 3
Full Text





HISTORIC NOTE


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
(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida




/ U C



Mimeographed Report SUB67-1 November, 1966

University of Florida
Institute of Food and Agricultural Sciences
SUB-TROPICAL EXPERIMENT STATION
18905 S.W. 280 Street
Homestead, Florida 33030


DISEASES OF KENAF IN DADE COUNTY, FLORIDA
AND THEIR RELATIONSHIP TO WINTER VEGETABLE PRODUCTION
by
C. W. Averre, III



Several hundred acres of kenaf (Hibiscus cannabinus L.) .(Mesta) were grown on
Rockdale soils during the summer of 1966 as a source of poles for propping pole
beans. In most cases kenaf was grown on land used for winter production of summer
squash (Cucurbita pepo melopepoo' (L.) Alef.), pole bean (Phaseolus vulgaris L.),
and ground tomato (Lycopersicon esculentum Mill.). Several compilations of diseases
affecting kenaf in other countries are Hartley, 1927 and Parrado, 1958 and for
South Florida Stoner et al., 1952, Pate 1952, and Summers, 1958) are available.
Since this is a crop new to the area several mature fields of kenaf were examined
in August and October for diseases. Disease information was needed since some of
the diseases may affect winter vegetable production. Unless specifically stated,
no critical tests for pathogenicity nor for identity of the causal agent were con-
ducted; identification of diseases was based on symptomotology and microscopic
examination of the pathogen.

Diseases observed

(1) Target leafspot caused by Pellicularia filamentosa (Pat.) Rogers (Rhizoctonia
solani Kuehn). Spots caused by this fungus are characterized by a cir-
cular light brown necrotic area bordered by a red halo and by the presence
of grey mycelium on the abaxial (underside) leaf surface (Crandall, 1948).
According to Parrado (1958) periods of high humidity favor disease develop-
ment, The stems may also become attacked and polygonal colorless spots
may develop. The incidence of disease observed initially was very low; it
was more prevalent in October.

(2) Powdery mildew caused by Leveillula taurica (Lev.) Arnaud. This fungus causes
yellowing of leaves and premature leaf fall. The spores and mycelium on
the abaxial leaf surface appears like a gray, dusty powder (Diehl, 1952).
The disease is worse during periods of high humidity (Parrado, 1958). The
disease was not serious in fields examined.

(3) Anthracnose caused by Colletotrichum hibisci Pollacci. The symptoms include
stunting of plants, deformation and wilting of the growing point,and ir-
regular bright red spots 5-10 cm in diameter on leaves that are usually
distorted. Spores develop in lesions on the main stem. Primary inoculum
probably originates from infected seedand secondary inoculum consists of
spores that develop in stem lesions. The fungus becomes systemic in the
plant largely in the phloem and the stunting and distortion symptoms are
probably caused by fungal metabolites. The disease was a limiting factor
of production in Cuba until the release of resistant varieties (Naito and
Toshikagu, 1953, and Parrado, 1958). The disease has been of no signifi-
cance in Dade County, and the only evidence of it was the presence of the







fungus in stem lesions. It was more severe in the fields visited in
October. This disease may become a problem if susceptible types are exten-
sively grown.

(4) White mold caused by Sclerotinia sclerotiorum (Lib.) dBy. The disease is
characterized by large lesions on stems which are covered with a white
mold. After a few days black sclerotia are observed in the infected areas.
The disease kills many seedlings and large plants. This fungus survives
in the soil as irregularly shaped sclerotia, 2-5 mm in size, and under
proper environmental conditions (after dormancy is broken), the sclerotia
form apothecia which produce ascospores which cause infection of the plant.
There is no secondary means of spread (Walker, 1952). The disease was
found at a very low frequency over a large area that had a crop of pole
beans during the previous winter; the disease had been observed in the
bean crop. So far as known, this is the first report of the disease on
kenaf in Florida. It was reported in New South Wales, Australia in 1954
(Annonymous, 1955).

(5) Root-knot nematode caused by Meloidogyne spp. (probably M. incognita Kofoid
and White, Chitwood). The symptoms of infected plants are well known and
include stunting of plants, poor leaf color, and large galls on the roots.
(Summers and Scale 1958). Infected plants tended to be concentrated in
circular areas about 100 ft. in diameter randomly distributed in the field.

Inoculations with Verticillium albo-atrum Reinke & Berth.

Because of the importance of verticillium wilt in Dade County (Conover, 1959 and
Strobel, 1960) and since many species in the Malvaceae are susceptible (okra,
Hibiscus esculentus L.; cotton, Gossypium hirsutum L.) to the wilt organism, inocu-
lations with a virulent tomato isolate were made by dipping 11-day old kenaf seed-
lings in a water suspension of spores and mycelium of the fungus. The seedlings
were transplanted to flats and kept in an air-conditioned laboratory to insure cool
temperatures for disease development. Okra seedlings (var. Clemson Spineless) were
inoculated in a similar manner. Five days after inoculation the okra seedlings
showed symptoms of the disease but the kenaf never did develop symptoms. The wilt
fungus was reisolated from the okra but not from the kenaf. It was concluded that
this variety of kenaf was not susceptible to this strain of Verticillium albo-atrum.

Discussion

With further planting of kenaf and further investigations, other diseases are like-
ly to be found. With the exception of one field that was badly infected with the
root-knot nematode the kenaf fields were remarkably free from disease and insects.
Kenaf has critical day length requirements (Ramos, 1958) so it must be grown in the
summer since short days induce flowering and stop vegetative growth. Since this is
the period of high rainfall, diseases associated with high soil moisture such as
damping-off caused by Pythium spp. and Phytophthora spp. can be expected in addition
to possible danger of loss from flooding.

The susceptibility of kenaf to the root-knot and white mold diseases which, also
affect vegetable crops, may present problems. The growing of kenaf on land to be
used for winter vegetable production should probably be avoided if these diseases
are present in the field.


Acknowledgment is given to Ing. Jorge L. Parrado for disease identifications and
other help.







fungus in stem lesions. It was more severe in the fields visited in
October. This disease may become a problem if susceptible types are exten-
sively grown.

(4) White mold caused by Sclerotinia sclerotiorum (Lib.) dBy. The disease is
characterized by large lesions on stems which are covered with a white
mold. After a few days black sclerotia are observed in the infected areas.
The disease kills many seedlings and large plants. This fungus survives
in the soil as irregularly shaped sclerotia, 2-5 mm in size, and under
proper environmental conditions (after dormancy is broken), the sclerotia
form apothecia which produce ascospores which cause infection of the plant.
There is no secondary means of spread (Walker, 1952). The disease was
found at a very low frequency over a large area that had a crop of pole
beans during the previous winter; the disease had been observed in the
bean crop. So far as known, this is the first report of the disease on
kenaf in Florida. It was reported in New South Wales, Australia in 1954
(Annonymous, 1955).

(5) Root-knot nematode caused by Meloidogyne spp. (probably M. incognita Kofoid
and White, Chitwood). The symptoms of infected plants are well known and
include stunting of plants, poor leaf color, and large galls on the roots.
(Summers and Scale 1958). Infected plants tended to be concentrated in
circular areas about 100 ft. in diameter randomly distributed in the field.

Inoculations with Verticillium albo-atrum Reinke & Berth.

Because of the importance of verticillium wilt in Dade County (Conover, 1959 and
Strobel, 1960) and since many species in the Malvaceae are susceptible (okra,
Hibiscus esculentus L.; cotton, Gossypium hirsutum L.) to the wilt organism, inocu-
lations with a virulent tomato isolate were made by dipping 11-day old kenaf seed-
lings in a water suspension of spores and mycelium of the fungus. The seedlings
were transplanted to flats and kept in an air-conditioned laboratory to insure cool
temperatures for disease development. Okra seedlings (var. Clemson Spineless) were
inoculated in a similar manner. Five days after inoculation the okra seedlings
showed symptoms of the disease but the kenaf never did develop symptoms. The wilt
fungus was reisolated from the okra but not from the kenaf. It was concluded that
this variety of kenaf was not susceptible to this strain of Verticillium albo-atrum.

Discussion

With further planting of kenaf and further investigations, other diseases are like-
ly to be found. With the exception of one field that was badly infected with the
root-knot nematode the kenaf fields were remarkably free from disease and insects.
Kenaf has critical day length requirements (Ramos, 1958) so it must be grown in the
summer since short days induce flowering and stop vegetative growth. Since this is
the period of high rainfall, diseases associated with high soil moisture such as
damping-off caused by Pythium spp. and Phytophthora spp. can be expected in addition
to possible danger of loss from flooding.

The susceptibility of kenaf to the root-knot and white mold diseases which, also
affect vegetable crops, may present problems. The growing of kenaf on land to be
used for winter vegetable production should probably be avoided if these diseases
are present in the field.


Acknowledgment is given to Ing. Jorge L. Parrado for disease identifications and
other help.







Literature Cited


Annonymous. 1955. New Plant diseases. Agr. Gaz. New South Wales 66(6):312.
Data source: Rev. Appl. Mycol. 35:162, 1956.

Conover, R. A. 1959. Verticillium wilt of tomato in Dade County, Florida.
Proceeding Fla. State Hort. Soc. 72:199-201.

Crandall, B. S. 1948. Pellicularia target spot leaf disease of kenaf and roselle.
Phytopathology 38: 503-505.

Diehl, W. W. 1952. Powdery mildew of kenaf in Florida. Plant Dis. Reptr.
36(2): 52.

Hartley, C. 1927. Notes on Hibiscus diseases in West Java. Phytopathology
17:25-27.

International Cooperation Administration. 1948. Proceedings of the World
Conference on Kenaf. International Cooperation Administration.
Washington 25, D. C. 288 p.

Pate, J. B. 1952. Preliminary reports of some of the diseases and pest problems
on kenaf, Hibiscus cannabinus L. in South Florida. Plant Dis. Reptr.
36:121-126.

Parrado, J. L. 1958. Diseases of kenaf in Cuba. In Proceedings of the World
Conference on Kenaf, pp. 113-123. International Cooperation Administration
Washington 25, D. C. 288 p.

Ramos, L. J. 1958. Photoperiodicity and kenaf. In Proceedings of the World
Conference on Kenaf, pp. 65-73. International Cooperation Administration.
Washington 25, D. C. 288 p.

Stoner, W. N., F. V. Stevenson, W. G. Genung, W. H. Thames, Jr., C. C. Seale,
E. 0. Gongstad and J. B. Pate. 1952. Preliminary reports of some of the
diseases and pest problems on kenaf, Hibiscus cannabinus L. in South
Florida. Plant Dis. Reptr. 36: 121-126.

Strobel, J. W. 1960. Studies of verticillium wilt disease in Florida. Proc.
Fla. State Hort. Soc. 73: 168-172.

Summer, T. W. 1958. Important diseases affecting kenaf in Florida. Proc. Soil
Crop Sci. Soc. Florida. 18: 323-326.

Summer, T. E. and C. C. Scale, 1958. Root-knot nematodes, a serious problem
of kenaf in Florida. Plant Dis. Reptr. 42: 792-795.

Walker, J. C. 1952. Sclerotinia disease. In diseases of vegetable crops. McGraw
Hill BookCo., New York. 529 p.




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