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i. I t Sourca and Rate Affect Severity of
\ '' ao'nthomona Leaf Spot of Hedera helix
SA. R. Chase1
University of Florida, IFAS
,,,FlpF g daresearch and Education Center Apopka
CFREgCapka Research Report, RH-89-1
Bacterial leaf spot of Hedera helix L. (English ivy) is caused by
Xanthomonas campestris pv. hederae T(Pammel) Dowson (1). The disease has
been reported from the majority of areas growing English ivy cultivars and
has caused serious problems for almost 60 years (2,7,10). Control of
bacterial leaf spot of ivy has been based on exclusion of contaminants from
the growing area as well as some preventative bactericide applications.
Since many cultivars of English ivy are sensitive to streptomycin sulfate
it is generally not used (9). The role of host nutrition in disease
severity has been studied on some other ornamental crops susceptible to
Xanthomonas including Brassaia actinophylla Endl. (schefflera) and
Schefflera arboricola H. Ayata (dwarf schefflera). In each case,
increasing fertilizer rate resulted in decreased disease severity (5).
Similar trends have been noted with other foliage plants (4,8). The
following research was conducted to determine the effect of nitrogen source
and rate on severity of Xanthomonas leaf spot of the English ivy cultivar
Materials and Methods
Plant production. Cuttings of H. helix 'Brokamp', chosen on the basis of
high susceptibility to the pathogen 9T, were rooted in Smither's Oasis
foam media under intermittent mist. After 4 weeks, a single rooted cutting
was planted into 6 inch plastic pots containing a steam-treated potting
medium. The medium consisted of 1:1 Canadian peat and pine bark and was
amended with 7 Ib dolomite and 1.0 lb Micromax per cubic yard, after steam-
treatment for 1.5 hours at 1900F.
Fifteen plants per treatment were used for each of two tests. Plants
were grown in a glasshouse with a maximum daily light level of 1800 ft-c
and temperatures ranging from 60 to 950F depending upon time of year. The
test included both rate and nitrogen source and was designed as a 3x3
factorial experiment. Nitrogen source was set at 100% nitrate, 50% nitrate
and 50% ammonium, and 100% ammonium and rates were x, 2x and 4x (where x =
recommended rate of 34.5 lb N/1000 ft2/yr) (6). Fertilizer was applied as
a liquid at the rate of 5 oz per 6 in pot. Two tests were conducted
between 21 April and 7 November 1988. Following a 3-month growth period
plants were rated as follows: total vine length, number of leaves greater
than 1 inch long, and top quality. Top quality was rated on the following
scale: 1 (dead); 2 (poor, unsalable); 3 (marginal, salable); 4 (good,
salable); and 5 (excellent, salable). In addition, in some tests, the
SProfessor of Plant Pathology, Central Florida Research and Education
i Center-Apopka, 2807 Binion Road, Apopka, FL 32703
fresh weight of tops for five representative plants per treatment was
recorded. Leachate electrical conductivity (EC) was recorded monthly using
the pour-through method (11).
Plants were inoculated by spraying with a suspension of the pathogen
(1 x 10 cells/ml) onto leaf surfaces with a pump action hand sprayer and
immediately covering with a plastic bag for 24 hours. Numbers of lesions
per plant were determined about 14 days after inoculation.
Results and Discussion
Growth response for Brokamp was consistent regardless of time of year
of the test. Total vine length was not affected significantly by nitrogen
source (Figure 1). Fresh weight of tops significantly decreased as
fertilizer rate increased but was not affected by nitrogen source. Top
quality was affected by both nitrogen source and rate. Generally
increasing rate decreased top quality with highest ratings for plant
receiving equal amounts of ammonium and nitrate (Figure 2).
Both nitrogen source and rate affected number of lesions on ivy.
Highest numbers of lesions occurred on plants fertilized with 50-50%
nitrate-ammonium nitrogen, with lowest number on those receiving 100%
nitrate nitrogen (Fig. 3). Increasing rate of any nitrogen source resulted
in decreased numbers of lesions per plant (Fig. 3).
Fertilizer rate has also been shown to affect severity of several
other bacterial diseases of foliage plants. Xanthomonas blight of
Syngonium podophyllum Schott 'White Butterfly' caused by X. campestris pv.
syngonii Dickey and Zumoff (3) and Xanthomonas leaf spots of schefflera and
dwarf schefflera, which is caused by Xch (5), also decrease as fertilizer
rate increases. Harkness and Marlatt found that increasing fertilizer to
Philodendron scandens C. Koch & H. Sello subsp. oxycardium (Schott) Bunt.
(heart-leaf philodendron) reduced severity of red-edge disease caused by X.
campestris pv. dieffenbachiae (Xcd) (Pammel) Dowson (8). Anthurium blight,
also caused by Xcd, is most severe at optimal fertilizer rates
(corresponding to optimal plant growth) (4). In general, overfertilized
plants appear to be less satisfactory hosts for many pathovars of X.
campestris than optimally fertilized plants.
Although overall rate of fertilizer applied to H. helix 'Brokamp'
affected plant growth, the source of nitrogen did not. Both factors,
however, affected the number of lesions caused by Xch, with decreased
numbers of lesions resulting from increases in fertilizer rate and highest
numbers of lesions on plants receiving either 50-50 or 75-25% nitrate-
ammonium nitrogen. Since nitrogen source does not influence plant growth,
use of either 100% ammoniacal or 100% nitrate nitrogen at twice the
recommended rate of 34.5 lb N/1000 ft /yr should reduce development of
Xanthomonas leaf spot on H. helix 'Brokamp'.
1. Arnaud, G. 1920. Une maladie bacterie-une du lierra (Hedera helix L.)
C. R. Hebd. Seances Acad. Sci. 171:121-122.
2. Burkholder, W. H., and Gutterman, C. E. F. 1932. Synergism in a
bacterial disease of Hedera helix. Phytopathology 22:781-784.
3. Chase, A. R. 1987. Effect of fertilizer rate on susceptibility of
Syngonium podophyllum 'White Butterfly' to Erwinia chrysanthemi or
Xanthomonas campestris. Foliage Digest 10(8):15-16.
4. Chase, A. R., and Poole, R. T. 1986. Effects of host nutrition on
growth and susceptibility of Anthurium scherzeranum to Xanthomonas leaf
spot. Nurserymen's Digest 20(6):58-59.
5. Chase, A. R. and Poole, R. T. 1987. Effects of fertilizer rates on
severity of Xanthomonas leaf spot of schefflera and dwarf schefflera.
Plant Disease 71:527-529.
6. Conover, C. A. and Poole, R. T. 1984. Light and fertilizer
recommendations for production of acclimatized potted foliage plants.
Foliage Digest 7(8):1-6.
7. Dye, D. W. 1967. Bacterial spot of ivy caused by Xanthomonas hederae
(Arnaud 1920) Dowson, 1939, in New Zealand. N. Z. J. Sci. 10:481-485.
8. Harkness, R. W., and Marlatt, R. B. 1970. Effect of nitrogen,
phosphorous and potassium on growth and Xanthomonas disease of
Philodendron oxycardium. J. Amer. Soc. Hort. Sci. 95:37-41.
9. Osborne, L. S., and Chase, A. R. 1985. Susceptibility of cultivars of
English ivy to two-spotted spider mite and Xanthomonas leaf spot.
10. White, R. P., and McCulloch, L. 1934. A bacterial disease of Hedera
helix. J. Agric. Res. 48:807-815.
11. Wright, R. D. 1986. The pour-through nutrient extraction procedure.
V X R A T E.... ...........................................................................
I I 2X RATE
N 60 C 4X RATE
NITRATE AMMONIUM-NITRATE AMMONIUM
Figure 1. Effect of nitrogen source and rate on vine length of
Hedera helix 'Brokamp'. Only rate of nitrogen significantly
affected vine length.
E5n X RATE
T 4 2X RATE
3 ......................... ............................... ... 2 X R A T E.......
S E'3 4X RATE
NITRATE AMMONIUM-NITRATE AMMONIUM
Figure 2. Effect of nitrogen source and rate on top quality of
Hedera helix 'Brokamp'. Both source and rate of nitrogen
affected top quality.
., ,., . . .iii :
\\. .... ......."" "'
.....\ ...... .:... .....
....A.E AM.NUMN.RTE AMONU
IT.... .... R. ...
Figure... 2..fcto.itoe.ou ..ndrt. n o uaiyo
Hedra elx ..rokp. ..... sorc.adrae.fniroe
U Ml X RATE
M 22 2X RATE
F o .
.3 -\...... ..... .. .
S 0 NITRATE AMMONIUM-NITRATE AMMONIUM
Figure 3. Effect of source and rate of nitrogen on susceptibility
of Hedera helix 'Brokamp' to Xanthomonas campestris pv.
hederae. Both source and rate of nitrogen affected number of