Group Title: CFREC-Apopka research report - Central Florida Research and Education Center-Apopka ; RH-90-23
Title: Effect of Osmocote rate on severity of Phytophthora stem rot of Aphelandra squarrosa 'Dania'
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Permanent Link: http://ufdc.ufl.edu/UF00065852/00001
 Material Information
Title: Effect of Osmocote rate on severity of Phytophthora stem rot of Aphelandra squarrosa 'Dania'
Series Title: CFREC-Apopka research report
Physical Description: 4 p. : ill. ; 28 cm.
Language: English
Creator: Chase, A. R ( Ann Renee )
Central Florida Research and Education Center--Apopka
Publisher: University of Florida, IFAS, Central Florida Research and Education Center-Apopka
Place of Publication: Apopka FL
Publication Date: 1990
 Subjects
Subject: Aphelandra -- Diseases and pests -- Control -- Florida   ( lcsh )
Phytophthora -- Control -- Florida   ( lcsh )
Fungal diseases of plants -- Control -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (p. 2).
Statement of Responsibility: A.R. Chase.
General Note: Caption title.
 Record Information
Bibliographic ID: UF00065852
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 70287587

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Effect of Osmocote rate on severity of Phytophthora
stem rot of Aphelandra squarrosa 'Dania'

A. R. Chase1

University of Florida, IFAS
Central Florida Research and Education Center Apopka
Pc" CFRIC Apopka Research Report, RH-90-23

The folywing report summarizes research performed to evaluate the potential
for use',&' fertilizer to lrduce severity of Phytophthora stem rot of Aphelandra
squarrosa 'Dani(a' Symptoms of Phytophthora stem rot are wilting and collapsed
stems due io rotting at the soil-line (1).

Materials and Methods

Plant production. Rooted cuttings of A. squarrosa 'Dania', obtained from
commerical producers, were used in two tests performed between 9 January and 2
August 1990. Plants were grown in 6 inch pots using a steam-treated medium
consisting of Canadian peat and pine bark (1:1, by volume). Light levels ranged from
2000 to 2600 ft-c. with temperatures between 65" and 95" F. Ten plants were used
for each of seven rates of Osmocote 19-6-12 (applied as a top-dressing): 0.7, 2.9, 5.1,
7.3, 9.5, 11.7, and 13.9 g/6 inch pot. The recommended rate for aphelandras under
these conditions is about 5 g (4). Plant height, number of leaves, quality and
leachate soluble salts [using the pour-through method (5)] were recorded 8 weeks
after fertilizer was applied. Plant quality was rated using the following scale: 1
(dead), 2 (poor, unsalable), 3 (marginal, salable), 4 (good, salable), and 5 (excellent,
salable).

Inoculation. Plants were inoculated, two months after fertilization, with a
mycelial slurry of Phytophthoraparasitica grown on potato-dextrose agar medium and
watered lightly into the potting medium.

Results

Leachate soluble salts increased as fertilizer rate increased and ranged from
300 to 6500 umhos/cm. Increasing the Osmocote rate also affected height, plant
quality, and number of leaves of aphelandra. Rates between 5.1 and 13.9 g
Osmocote gave good growth (Fig. 1 3). Only plants receiving the lowest rate of
fertilizer (0.7 g) showed substantially reduced growth.

'Professor of Plant Pathology, Central Florida Research and Education Center -
Apopka, 2807 Binion Road, Apopka, FL 32703.








The severity of stem rot caused by P. parasitica was rated on a scale from 1
(no disease) to 5 (dead) was highest for plants receiving 9.5 g or higher rates of
Osmocote (Fig. 4). None of the underfertilized plants showed any signs of stem
rot.
Summary

When fertilizer rate is to be used as a cultural control method several factors
must be considered. Rates which reduce disease significantly must not result in plant
damage, excessive costs (due to high rates), or significantly increased potential for
ground water contamination. Fertilizer rates which result in the lowest severity of
Phytophthora stem rot of Aphelandra corresponded to best plant growth (about 3 to
7 g Osmocote 19:6:12/6" pot). This range of rates is close to those previously
recommended for production of Aphelandra. An additional consideration is that
fertilizer rates used to decrease one disease should not increase the potential for
other diseases. Previous research on Aphelandra and Dieffenbachia showed that
increased fertilizer levels resulted in increased severity of Myrothecium leaf spot
disease (2, 3). Fertilizer rates which reduce severity of Phytophthora stem rot of
Aphelandra would probably reduce severity of Myrothecium leaf spot as well.

Literature Cited

1. Chase, A. R. 1981. Phytophthora stem rot of Aphelandra squarrosa. Plant
Disease 65:921-922.

2. Chase, A. R., and R. T. Poole. 1985. Host nutrition and severity of
Myrothecium leaf spot of Dieffenbachia maculata 'Perfection'. Scientia
Horticulturae 25:85-92.

3. Chase, A. R., and R. T. Poole. 1986. Effect of nutrition on growth of
Aphelandra squarrosa and its susceptibility to Myrothecium leaf spot.
Nurserymen's Digest 20(6):71-72.

4. Conover, C. A., and R. T. Poole. 1984. Light and fertilizer recommendations
for production of acclimatized foliage plants. Foliage Digest 7(8):1-6.

5. Wright, R. D. 1986. The pour-through nutrient extraction procedure.
HortScience 21(2):227-229.





Figure 1. Effect of Osmocote 19-6-12 rate on height of Aphelandra
squarrosa 'Dania'.


Height (inches)
61


K


X


0.7 2.9


5.1 7.3 9.5


g Osmocote/6 inch pot

Figure 2. Effect of Osmocote 19-6-12 rate on number of leaves on
Aphelandra squarrosa 'Dania'.


Number leaves


15 -


10-


0.7 2.9 5.1 7.3 9.5 11.7
g Osmocote/6 inch pot


13.9


s








Figure 3. Effect of Osmocote 19-6-12 rate on plant quality of
Aphelandra squarrosa 'Dania'. Plant quality was rated on a scale
from 1 (dead) to 5 (excellent, salable).
Plant quality


5.1 7.3 9.5 11.7


13.9


g Osmocote/6 inch pot

Figure 4. Effect of Osmocote 19-6-12 rate on severity of stem rot
disease on Aphelandra squarrosa 'Dania' caused by Phytophthora
parasitica. Disease severity was rated from 1 (no disease) to 5
(dead).


Disease


severity


2.5 F


2-


5.1 7.3 9.5
g Osmocote/6 inch pot


13.9


i




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