Group Title: CFREC-Apopka research report
Title: Effect of fertilizer rate on susceptibility of 'Mikado' begonia to Xanthomonas campestris pv. begoniae
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 Material Information
Title: Effect of fertilizer rate on susceptibility of 'Mikado' begonia to Xanthomonas campestris pv. begoniae
Series Title: CFREC-Apopka research report
Physical Description: 3, 4 p. : ill. ; 28 cm.
Language: English
Creator: Shaw, D. Michael
Chase, A. R ( Ann Renee )
Central Florida Research and Education Center--Apopka
Publisher: University of Florida, Central Florida Research and Education Center-Apopka
Place of Publication: Apopka FL
Publication Date: 1991
Subject: Begonias -- Diseases and pests -- Control -- Florida   ( lcsh )
Begonias -- Fertilizers -- Florida   ( lcsh )
Xanthomonas campestris -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
Bibliography: Includes bibliographical references (p. 3).
Statement of Responsibility: D. Michael Shaw and A.R. Chase.
General Note: Caption title.
 Record Information
Bibliographic ID: UF00065310
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 70069698

Full Text

/I / Effect of Fertilizer Rate on Susceptibility of 'Mikado' Begonia arston Sc e
to Xanthomonas campestris pv. begoniae L b.,, n

D. Michael Shaw and A. R. Chase' 3 0 1994

University of Florida, IFAS, ioeirsity of
Central Florida Research and Education Center Apopka
CFREC-Apopka Research Report, RH-91-9

"One of the oldest known bacterial diseases of a foliage plant is caused by Xanthomonas
campestris" (6). Because of the range of plants that X. campestris infects, serious losses occur
in the ornamental industry yearly warranting extensive research regarding control. Xanthomonas
diseases cause serious losses in the ornamental industry affecting many different commercially
grown plants (5).

Xanthomonas campestris is a difficult disease to control; therefore, "an integrated
approach to disease control should include as many factors as possible" (6). Several methods
employed in combating X. campestris include bactericides, fertilizer rates and sources and
cultural changes in the greenhouse environment. Bactericides are commonly used for disease
control on some hosts but are not very effective and may be phytotoxic to the plant (4).
Attempts to control bacterial diseases should include elimination of overhead irrigation (4) as
well as manipulating fertilizer rates supplied to the host plant. Previous work has shown that
by increasing rates of fertilizer it is possible to lower the rate of infection of X. campestris on
a variety of ornamental plants (1,2,3). Furthermore, since X. campestris is a motile organism
flagellaa), adequate crop spacing can eliminate physical contact between plants, making it less
likely for infection to pass from one plant to another.

Although increasing rates of fertilizer seems to reduce X. campestris infection, it can also
have negative effects on the host plant. For example, higher rates may cause leaf burn, root
damage, and growth inhibition. Other considerations that must be taken into account are the
concern for ground water contamination due to fertilizer leachate and the cost of the fertilizer

This report evaluates the effect of fertilizer rate on severity of Xanthomonas campestris
on Begonia rex-cultorum cv. Mikado. A rate of fertilizer which is capable of reducing the rate
of Xanthomonas infection without causing damage to the host plant would be ideal. With this
type of control it may be possible to lower the amount of bactericides applied.

'Technical Assistant and Professor of Plant Pathology, respectively, CFREC-Apopka, 2807
Binion Rd., Apopka, FL 32703.

Materials and Methods

Rooted cuttings of Begonia rex-cultorum cv. Mikado were obtained from a local
commercial foliage grower. Eighty plants were used in a test begun 21 January 1991 and
terminated 22 April 1991. Plants were grown in a steam-treated medium consisting of one part
Canadian peat and one part pine bark (1:1 v:v). Four rates of slow-release fertilizer (Osmocote
19-6-12, Grace-Sierra, Milpitas, CA 95035) were used: 1, 6, 11 and 16 grams per 6 inch pot.
Light levels ranged from 1500 to 2500 ft-c. Plant height, number of leaves, leaf length, leaf
width, top grade (plant quality), leachate soluble salts [using pour-through method (1)] were
recorded as well as fertilizer damage and disease symptoms produced by X. campestris.

INOCULATION: Plants were placed in intermittent mist (15 sec/30 min for 12 hr day) 1 day
prior to inoculation and were inoculated with a solution of Xanthomonas campestris pv. begoniae
(1 x 107 colony forming units per ml) by a hand sprayer onto leaf surfaces. After inoculation,
plants were placed in plastic bags for 24 hours, with mist treatment continuing until termination
of the experiment.

Results and Discussion

Twenty-one days after fertilizer application plant height remained comparable for plants
treated with 6, 11, and 16 g/6-inch pot. Forty-nine days after treatment, significant differences
were seen, with plants receiving the highest rate of fertilizer (16g) being most stunted. The
effects of fertilizer on total number of leaves were also substantial with that of Ig having the
most leaves to 16g having the least leaves (Figs. 1 and 2). Leaf length and leaf width did not
show a significant difference statistically, but some trends were recorded (Figs. 3 and 4). It was
shown that there were slight differences in plant quality due to fertilizer levels, where plant
quality was based on a scale of 1-5 (1=dead, 2=not salable, 3=salable, 4=good, salable,
5 =excellent quality plants) (Fig. 5). Leachate soluble salts increased as fertilizer rates increased
with all soluble salts levels lower after 49 days as compared to 21 days (Fig. 6). The extent of
fertilizer damage was significant in that plants receiving 1 or 6g showed the least amount of
damage; those receiving 11 or 16g showed increasing levels of damage in order of fertilizer rate
(Fig. 7).

Xanthomonas damage was significantly affected by fertilizer levels (Pr > F 0.0001).
Plants receiving 16g showed less than 1% damage due to Xanthomonas while those receiving
1 or 1 g showed significantly higher rates of damage. Plants receiving 6g Osmocote showed
comparatively less damage than plants with 1 and 11g. This may be a result of insufficient
replications, since disease severity rating varied widely. Past literature has shown that
increasing to 20 or more replicates can eliminate these unusual dips, since the degree of
variation is reduced.


trnmmnA itr

er-ApopKa, Kesearcn Keport, Knu-u-y.

1989. Effect of Osmocote rate on severity of Xanthc
University of Florida, IFAS, Central Florida Resea
Research Report, RH-89-11.

1988. Effect of fertilizer level on severity of Xanthc
2. Proc. Fla. State Hort. Soc. 101:339-340.

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Plant Height


8 11 16
g Osmocote/6 inch pot
Figure 1. Effect of Osmocote 19-6-12
rate on plant height of Mikado Begonia.

Number of Leaves

7////]// _

g Osmocote/6 inch pot
e 2. Effect of Osmocote 19-6-12 on
iber of leaves on Mikado Begonia.


---------- ^III III III

I I -


Leaf Length


1 6 11 16
g Osmocote/6 inch pot
Figure 3. Effect of Osmocote 19-6-12
rate on leaf length of Mikado Begonia.

Leaf Width


16 11 6
g Osmocote/6 inch pot
Figure 4. Effect of Osmocote 19-6-12
rate on leaf width of Mikado Begonia.

Plant Top Grade

Top Grade

1e n ie
6 11 16
g Osmocote/6 inch pot
Figure 5. Effect of Osmocote 19-6-12 on
top grade; evaluated on a scale from
5 (excellent salable) to 1 (dead).

Soluble Salts



g Osmocote/6 inch pot
Figure 6. Effect of Osmocote 19-6-12
on soluble salts of Mikado Begonia.

Days After Treatment
M 21 days = 49 days

4000 -1




0 -

V__ I1



Fertilizer Damage

Damage Rating

4 -

1 6 11 e16
g Osmocote/6 inch pot
Figure 7. Effect of Osmocote 19-6-12
rate on damage of plant tissue. Based
on a scale from 5 (dead) to 1 (none).

Xanthomonas Damage

Percentage of Infection


10% -





16 11 16
g Osmocote/6 inch pot
Figure 8. Effect of Osmocote 19-6-12 on
percentage of damage caused by
Xanthomonas blight.

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