Group Title: CFREC-Apopka research report
Title: Fungicide tests for control of Phytophthora and Pythium diseases on ornamentals
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Permanent Link: http://ufdc.ufl.edu/UF00065293/00001
 Material Information
Title: Fungicide tests for control of Phytophthora and Pythium diseases on ornamentals
Series Title: CFREC-Apopka research report
Physical Description: 6 p. : ill. ; 28 cm.
Language: English
Creator: Chase, A. R ( Ann Renee )
Mellich, T. A ( Terri A. ), 1958-
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: 1992
 Subjects
Subject: Plants, Ornamental -- Diseases and pests -- Control -- Florida   ( lcsh )
Fungicides -- Testing -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: A.R. Chase and T.A. Mellich.
General Note: Caption title.
 Record Information
Bibliographic ID: UF00065293
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 - 70006766

Full Text
/lo


'RD Fungicide Tests for Control of Phytophthora
q -n and Pythium Diseases on Ornamentals

A.R. Chase and T.A. Mellich' r'o S i.n
s.0 Scienco
University of Florida, IFAS,
Central Florida Research and Education Center Apopl&EP 3 0 1994
CFREC-Apopka Research Report, RH-92-9
University of Florida
Fungicides have continued to be an important element of the disease control techniques
used by many ornamental producers. A quaternary ammonium compound (Greenshield from
Whitmire) and a numbered compound from ISK Biotech (ASC-66825, fluazinam) are two
products with unknown activity ranges on diseases of ornamental crops. In addition, tests
included metalaxyl (Subdue 2E) and fosetyl aluminum (Aliette 80WP) to provide standard
controls as well as provide information for label expansion. Some of the most important
diseases caused by soilborne fungi are root and stem rots caused by Phytophthora and Pythium
species. The specific diseases which were researched during the past year were: Phytophthora
stem rot of zebra plant, Phytophthora stem rot and aerial blight of vinca, and Pythium root rot
of schefflera.

PHYTOPHTHORA STEM ROT OF ZEBRA PLANT

Phytophthora stem rot of zebra plant (Aphelandra squarrosa) is caused by Phytophthora
parasitica which is a pathogen of many flowering, foliage, and bedding plants. Treatments
included noninoculated and inoculated controls, metalaxyl (Subdue 2E at 3.5 oz per 100 gallons),
ASC-66825 (fluazinam from ISK Biotech at 4 and 16 oz per 100 gallons), and a quaternary
ammonium compound (Greenshield at 1, 2, and 4 oz per 100 gallons). Subdue was applied as
a drench on 6 December and ASC-66825 treatments were applied as drenches on 6 and 19
December 1991. Greenshield treatments were sprayed onto the plant base on a daily schedule
from 3 to 19 December 1991. Plants were inoculated with Phytophthora parasitica (87-10) on
9 December and the degree of stem rot and plant collapse was evaluated on 20 December 1991.
Disease severity was rated on the following scale: 1 = no disease; 2 = slight wilt or rot of one
leaf; 3 = moderate wilt or rot of 2 to 4 leaves; 4 = severe wilt; and 5 = dead. Subdue and
ASC-66825 drenches gave good control of Phytophthora stem rot on zebra plant (Fig. 1).
Applications of Greenshield on inoculated plants gave more severe disease symptoms than the
inoculated control plants and grew more severe as the rate of Greenshield increased. In a
separate test, healthy (noninoculated) zebra plants were treated with the same rates of
Greenshield and developed no symptoms of disease or phytotoxicity. These results indicate that
Greenshield increased severity of Phytophthora stem rot on zebra plant.





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







PHYTOPHTHORA STEM ROT AND AERIAL BLIGHT OF VINCA

Phytophthora stem rot of vinca (Catharanthus roseus) is also caused by Phytophtho
parasitica. Treatments included noninoculated and inoculated controls, fosetyl aluminum (Aliel
80WP at 16 and 32 oz per 100 gallons), metalaxyl (Subdue 2E at 2 oz per 100 gallons), aj
ASC-66825 (4 and 16 oz per 100 gallons). Subdue was applied as a drench on 17 October a
other treatments were applied as drenches on 17 and 31 October 1991. Plants were inoculat
with Phytophthora parasitica (91-37A) on 21 October and the percentage of the plant showii
wilt and stem rot was evaluated on 4 November 1991. All of the fungicide drenches ga
excellent control of this disease on vinca (Fig. 2). No evidence of phytotoxicity was noted.

PYTHIUM ROOT ROT OF SCHEFFLERA

Pythium root rot of schefflera (Brassaia actinophylla) is caused by Pythium splende
which is the most common species of Pythium infecting foliage crops. Two tests we
completed with this disease of schefflera. Treatments in the first test included noninoculated a
inoculated controls, metalaxyl on both noninoculated and inoculated plants (Subdue 2E at 2







ie best ti


)wth was found on plants treated with the Subdue drench (Table 1). Good
urred on plants treated with the high drench rate of Aliette 80WG and the
ich of Aliette 80WG and Chipco 26019. Other treatments gave a lesser degree


'idence of phytotoxicity was noted.

CONCLUSIONS

These tests indicate that Subdue remains one of the best fungicides for controlling both
iytophthora and Pythium diseases on ornamentals. In addition, Aliette provides good control
' Pythium root rot on schefflera when used as a drench but not as a spray. The use of
reenshield on zebra plants inoculated with Phytophthora resulted in worse disease than if they
td not been sprayed. Always be careful when trying new products on your crops since this
pe of problem can occur even when overt symptoms of phytotoxicity are absent. The
imbered compound ASC-66825 has proven to have activity against a stem rot caused by
lytophthora but not Pythium root rot. Further testing with this product is required before its
ae range of activity is known.







Table 1.


Effect of Aliette 80WG, Subdue 2E, Chipco 26019 50WDG, and Aliette 80WP
on height and root and top growth of schefflera (Brassaia actinophylla) infected
with Pythium splendens.


Treatment Rate/100 Height (in) Percent roots Top weight
gallons 17 Mar 18 Mar (g) 18 Mar
Noninoculated 7.5 ab 35.5 abc 34.4 abc
Inoculated 7.5 a 34.5 abc 34.6 abc
Aliette 80WG 2.5 lb 7.9 a 56.0 abcd 37.9 abc
spray
Aliette 80WG 5.0 lb 8.0 a 63.5 cd 40.7 abc
spray
Subdue 2E 2 oz 8.7 a 72.0 d 55.0 d
Chipco 26019 50WDG 1.0 lb 7.7 a 32.0 ab 31.5 a
Aliette 80WG 2.5 lb
Chipco 26019 50WDG 0.5 lb 8.6 a 61.5 bcd 44.0 bc
Aliette 80WG 0.4 lb
Aliette 80WP 2.5 lb 7.6 a 47.5 abcd 31.7 a
spray
Aliette 80WP 5.0 Ib 7.7 a 29.0 a 32.7 ab
spray
Aliette 80WG 0.4 lb 8.3 a 73.4 d 43.1 abc
Aliette 80WG 0.8 lb 8.2 a 59.0 bcd 45.2 cd
* Spray treatments were applied to the point of drip on 6 February and 4 March 1992. All
other treatments were applied as a drench at about 1 pint/ft2 of pot surface area on the
same dates.

b Numbers in the same column followed by different letters were significantly different
using Duncan's New Multiple Range Test, P = 0.05.








Figure 1.


Effect of Subdue 2E, ASC-66825, and Greenshield on severity of Phytophthora
stem rot of zebra plant (Aphelandra squarrosa) caused by Phytophthora
parasitica.

Disease rating


Disease rating: 1-none, 2-slight,
3-moderate, 4-high, 5-dead


0
Noninoc Inoo Subdue 66825 66825 Grnshid Grnshid Grnshid
ulated ulated 3.5 oz 4 oz 16 oz 1 oz 2 oz 4 oz
Treatment

Figure 2. Effect of Aliette 80WP, Subdue 2E, and ASC-66825 on Phytophthora stem rot
and aerial blight of vinca (Catharanthus roseus) caused by Phytophthora
parasitica.


Percent diseased


- ~I


Aliette Aliette
16 oz 32 oz


Subdue 66825 66825
2 oz 4 oz 16 oz


Treatment


Noninoc
ulated


Inoc
ulated







Figure 3. Effect of Subdue 2E and ASC-66825 on root and top growth of schefflera
(Brassaia actinophylla) infected with Pythium splendens.


Noninoc Inoc Subdue Subdue 66825
ulated ulated noninoc Inoc 4 oz
Treatment

S Percent roots M Fresh weight tops


66825
16 oz




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