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Group Title: Belle Glade EREC Research Report - University of Florida Institute of Food and Agricultural Sciences ; EV-1992-2
Title: Chemical control of powdery and downy mildew of squash at Belle Glade, Florida in 1992
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Permanent Link: http://ufdc.ufl.edu/UF00074971/00001
 Material Information
Title: Chemical control of powdery and downy mildew of squash at Belle Glade, Florida in 1992
Series Title: Belle Glade EREC Research Report
Physical Description: 5 leaves : ; 28 cm.
Language: English
Creator: Pohronezny, Ken, 1946-
Everglades Research and Education Center
Publisher: Everglades Research and Education Center
Place of Publication: Belle Glade Fla
Publication Date: 1992
 Subjects
Subject: Squashes -- Diseases and pests -- Florida   ( lcsh )
Powdery mildew diseases -- Florida   ( lcsh )
Downy mildew diseases -- Florida   ( lcsh )
Agricultural extension work -- Research   ( lcsh )
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (leaf 2).
Statement of Responsibility: Ken Pohronezny ... et al..
General Note: Caption title.
 Record Information
Bibliographic ID: UF00074971
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 70843757

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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













CHEMICAL CONTROL OF POWDER NY DbEW OF SQUASH



IFAS, University of Florida, Everglades Reseach and Education
Center (EREC), Belle Glade.


INTRODUCTION

Powdery and downy mildew continue to be two of the most
serious foliar diseases of summer squash grown in southern Florida.
These studies were carried out to evaluate several fungicides for
control of both powdery and downy mildew and to measure any yield
affects associated with disease control.


MATERIALS AND METHODS
Summer squash was mechanically seeded using a planter junior
into a Pahokee Muck soil (pH = 6.4) on the EREC farm on 24 February
1992. Summer squash cultivar Early Yellow Summer Crookneck was
used to plant four replications of each treatment in a randomized
complete block design. Test plots consisted of four rows, each 20
ft (6.1 m) long on 6 ft (1.8 m) centers. Fertilizer according to
soil test recommendations was broadcast and incorporated prior to
bed construction.

All test materials were applied with a CO2 powered backpack
sprayer at a pressure of 25 lb/in2 (17.24 newtons/cm ). The volume
of finished spray increased from 72 to 144 gal/acre (672-1344 L/ha)
as the plants increased in size. Larvin was applied weekly for
insect control using a self-propelled high pressure, high volume
commercial spray unit. Development of powdery mildew and downy
mildew was slow at first but by the last week of April there was a
substantial amount of both powdery and downy mildew. There was
also a much higher level of watermelon mosaic virus evident in the
beds than expected.

Experimental treatments, rates, and frequency of application
are shown in Table 1. Weekly sprays were applied 17 March, 24
March, 30 March, 7 April, 14 April, 21 April, and 29 April.

The severity of powdery and downy mildew was evaluated on 4
May. As coalescence made it difficult to discern individual foci,
estimates were made of the percentage of leaf surface covered with








mildew. Adaxial surface ratings are shown for powdery mildew and
downy mildew and abaxial ratings for powdery mildew only.

Plots were harvested twice a week from 9 April until 1 May.
All fruit from the two interior rows of each plot were picked and
graded. Records were taken of the weight of marketable fruit and
oversize fruit. Combined data from six individual harvests are
presented in this paper.

All disease severity and yield data were subjected to analysis
of variance, followed by a means separation according to Waller-
Duncan's methods. Percentage data were converted to arcsine square
root equivalents before analysis (1).


RESULTS AND DISCUSSION

Very little powdery or downy mildew was seen in plots before
first fruit set. The late onset of these diseases may explain the
lack of significant differences in yield between treatments.

The Bravo formulation seems to provide relatively good control
of both diseases. Disease ratings for downy mildew and powdery
mildew on the adaxial surface were lowest for Bravo 825 on 4 May
(Table 2). There were no significant differences between
treatments when powdery mildew was evaluated on abaxial leaf
surfaces. This may be related to the method of application of the
fungicides. With the nozzle arrangement on the boom of the
backpack sprayer, most of the fungicide spray was deposited on the
adaxial leaf surfaces.

Sulfur did not provide the control of powdery mildew seen in
some past tests (2,3). Further evaluations are needed to see if
sulfur is less efficacious for powdery mildew than previously
thought. Aliette provided fairly good control of downy mildew but
not of powdery mildew. The addition of a copper fungicide (Kocide
101) to the Aliette with appropriate buffering did not enhance its
activity against powdery mildew.


LITERATURE CITED

1. Gomez, K. A., and Gomez, A. A. 1984. Statistical Procedures
for Agricultural Research. John Wiley & Sons. New York, New
York. 680 pp.

2. Pohronezny, K., Dankers, W., and Sherman, R. 1989. Chemical
control of powdery mildew of yellow squash at Homestead,
Florida in 1989.

3. Sonoda, R. M., and K. Pohronezny. 1983. Status and potential
of pesticide resistance among fungal and bacterial pathogens
of vegetable crops in south Florida. Proc. Fla. State Hort.
Soc. 96:66-69.








Table 1. Fungicide treatments evaluated for control of powdery
mildew and downy mildew of squash at Belle Glade, FL in
1992a

---Treatment ----- -Rate/100 gal
Treatment Rate/ba0 Qal


1) Aliette


3 lb

2 lb


2) Kocide 101


3) Aliette + Kocide + K2CO0

4) Bravo 720

5) Bravo 825

6) Bravo 720 alt/w Omni

7) Super Six sulfur 6F


3 lb + 2 lb + 1.8 lb

1.5 pt

1.4 lb

1.5 pt alt/w 3.0 pt


1 qt


8) Control (H20)


"All treatments applied with a CO2 powered backpack sprayer at a
pressure of 25 lb/in2, in a volume of water equal to 72-144
gal/acre.









Table 2.


Disease ratings for powdery and downy mildew of squash
experiment, Belle Glade, FL 4 May 1992a


P= = =P= I =~= 1=-3 I- -= = =


Treatment


4 Powdery Mildew
Adaxial Surface Abaxial Surface


% Downy Mildew


Aliette

Kocide

Control


Super Six Sulfur

Combob


Bravo 720


Bravo 720/Omni

Bravo 825


25.5 a

20.4 ab

19.1 ab

16.4 ab

15.6 ab

15.2 ab

11.1 b

2.9 b


30.2 ns

30.5

32.9


22.4

35.5

22.1

23.1

25.2


27.5 bc

37.2 ab

47.3 a

38.0 ab

24.7 ab

20.1 bc

21.9 bc

16.9 c


"Based on means of four replications of each treatment arranged in
a randomized complete block design. Ratings are composites for
five midcanopy leaves taken from the interior two rows of each
plot.


bKocide+Aliette+K2CO3


^ ~ ~ Ad x a su f c Ab x a qur--face-.- --- __ ,^,-.^ ^^_ ^ ^ ^^ __^__









Table 3. Yields in squash plots affected by powdery and downy
mildew at Belle Glade, FL 19920


YIELD


Treatment

Control

Aliette

Kocide

Combod

Bravo 720

Bravo 825

Omni/Bravo 720

Super Six


Marketable Weightc


55.59

57.21

66.12

64.60

59.86

57.49

70.59

53.61


Total Weightb

67.73

68.59

80.14

74.32

72.08

73.29

89.73

67.73


aBased on twice weekly harvest from 9 April until 1 May.
The two interior rows (40 row ft) were used for yield
determinations.

bIncludes oversized fruit.

cExpressed in kg/plot.

dKocide+Aliette+K2CO3




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