2007 Extension Research Report
Disease Management
ISAGRO RICERCA SOIL DRENCH APPLICATIONS FOR MANAGEMENT OF
PHYTOPHTHORA CAPSICI ON YELLOW SQUASH AND TOMATO
A.S. Csinos, Ph.D., Scott Monfort, Ph.D., Unessee Hargett, and Lara Lee Hickman, Department of Plant
Pathology, University of Georgia-CPES, P.O. Box 748, Tifton, Ga. 31793
treatments and 5 replications.
Each plot was inoculated with P. capsici
infested vermiculite on 9 August and again on
25 September by placing 1/8 teaspoon of P.
capsici infested beet seed (approximately 15-20
seed per location) in the crown of the plant in
three locations, beginning, middle and end of
plot. Fungal inocula was produced by plating
pure cultures of Phytophthora capsici on V8agar plates and incubating for 7-10 days.
Inoculum of P. capsici vermiculite was
produced by adding 250ml of V8 broth (200ml
of V8, 800 ml of distilled water, 2g of CaCO3
per liter) to 500 cm3 of vermiculite. Flasks
containing V8 vermiculite were autoclaved for
one hour. After autoclaving, flasks containing
V8 vermiculite medium were allowed to cool
and then inoculated with V8 agar plugs of P.
capsici (approximately 1/4”x 1/4” diameter
plugs) under a laminar flow hood using aseptic
techniques. Flasks were allowed to incubate at
26 degrees Celsius for 10-14 days before field
inoculation.
P.capsici on beet seed (Detroit Medium
Top variety) was produced by soaking beet seed
in distilled water in aluminum pans for 24 hours.
Soaked beet seed was decanted and then poured
into 500ml flasks to the 250-300ml mark,
plugged with Identi-plug™ foam plugs,
covering plugs with foil and securing with
autoclave tape. Flasks were then autoclaved for
30 minutes. After autoclaving, flasks were
allowed to cool and then inoculated with V8
agar plugs of P. capsici (approximately 1/4”x
1/4” diameter plugs) under a laminar flow hood
using aseptic techniques. Flasks were allowed to
incubate at 26 degrees Celsius for 10-14 days
before field inoculation
Introduction
Phytophthora capsici is a soilborne
disease that has become a serious threat in the
production of cucurbits, pepper and tomato
crops. The disease affects all parts of the plant
including roots, stems, plant crowns, and fruit.
The disease can cause heavy crop losses and
may even force growers to move production to
other areas due to the ability of the fungus to
persist in the soil for several years. To date
there is no effective method of controlling
Phytophthora capsici and further research needs
to be done to develop better strategies for
managing the disease. This trial evaluates the
effectiveness of several chemical control agents
as compared to and in combination with a
biological application.
Methods and Materials
The study was located at the Black
Shank Farm, Tifton, Georgia in Block 1240Pcap area 1 & 2 of the Phytophthora capsici
nursery. The test area was fertilized on 31 July
with a 10-10-10 formulation applied at 500lb/A.
Fertilizer was applied and then roto-tilled into
the soil. On 09 August, test area was prepared
and beds were shaped and covered with 1 mil
black polyethylene film mulch and plumbed
with drip tape installed simultaneously in the
center of the bed approximately 1-inch deep.
The drip tape was Aquatraxx™ brand with a
12-inch emitter spacing, and a flow rate of .45
gal/min/100ft with a 12-PSI regulator. Plastic
mulch covered plots were 30 inches wide, 30
feet in length with an average of 15 squash
plants and 15 tomato plants and 5-foot alleys
between plots. The plot design was a
randomized complete block (RCBD) with 12
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The test was planted with both yellow
crook neck squash in one half of the plot and
tomato in the other half of each plot.
Commercial plant cultivars were ‘Prelude II’
yellow crook neck squash and ‘Quincy’ tomato.
Approximately 16 squash plants and 15 tomato
plants were planted in each plot on 17 August.
Plant spacing for squash was 12" and 18" for
tomato. Squash and tomato seedlings were
transplanted using a mechanical transplanter
that cuts holes in the center of the plastic and
adjacent to the drip tape just ahead of the
planters.
Additional fertilizer was applied
through the drip lines to all plots throughout the
growing season at a rate. Pesticide applications
were made weekly to control aphids and
whitefly. Admire Pro at the rate of 4oz/A was
applied through the drip tape on 18 and 25
August, and 01, 08, 14, and 28 September.
Individual treatments were made 7-days
before transplanting (10 August- Treatments 5
& 7), at transplanting (17 August- Treatments 57 & 9-12), four weeks after transplanting (06
September- Treatments 2-4 & 8-12), and 4
weeks before 1st harvest (27 September Treatments 2-4 & 8-12). All treatments were
applied through the drip line simultaneously
using the Hickey Injection System, with an
injection period of four hours.
Plant vigor ratings were conducted on
05 September and 20 September. Vigor ratings
were conducted on a 1-10 scale with 10
representing live and healthy plants and 1
representing dead plants. Stand counts were
made to record live plants, any diseased or dead
plants and to determine if any phytotoxicity was
occurring on plants. Counts were conducted on
25 and 28 August, 05, 12, 20 and 25 September,
and 11 October.
Plots were irrigated with additional
overhead water twice a day beginning on 29
September and ending on 06 October. Each
irrigation time was fifteen minutes long with
1/4" of water being applied equaling ½"
additional irrigation water per day.
The squash crop was hand harvested
with each harvest being separated into
marketable and cull fruits, counted, and
weighed. Squash harvests were conducted first
since this crop matures and produces earlier
than tomato. Squash harvests were conducted
on 15, 22, and 28 September with the final
harvest being taken on 06 October. Squash fruits
are considered harvestable when the blossom
has fallen off.
The tomato crop was hand harvested
with each harvest being separated into
marketable and cull fruits, counted and weighed.
Tomatoes were harvested one time only and
were harvested green due to possible loss of
plants to cold temperatures and frost. Tomato
harvest was conducted on 13 November.
All data was collected and analyzed
using SAS 9.1 with an analysis of variance
(P=0.05) and means were separated using LSD.
Summary
The fall of 2006 was unusually dry and
thus disease pressure was low. Although plots
were initiated in an infested field, and plots
were inoculated at transplant, very little disease
developed.
Very little differences occurred among
treatments for yield at the P=0.05 level of
probability. The lowest disease occurred with
Ridomil Gold applied at-plant, 4 weeks after
transplanting, and 8 weeks post planting for
yellow squash.
No differences (P=0.05) in yield
occurred in tomato among treatments although
Kiralaxyl plus Remedier (Treatment 7) had the
highest yield numerically. The lowest level of
disease occurred with treatment 7, Kiralaxyl
plus Remedier, and was significantly lower than
the Ridomil Gold standard.
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Table 1. Treatment List and Field Application Schedule- Isagro Ricerca Soil Drench
Applications for Management of Phytophthora capsici on Yellow Squash
Fall 2006 Trial, Black Shank Farm, Tifton, Georgia
Treatments
Rate
Application Code
____________________________________________________________________________________________
1.
Untreated Control
---------------
-----
2.
IR6141 Kiralaxyl 50WP
@ 1.06 lb/A
C, D
4.
IR6141 Kiralaxyl 50WP
@ 2.12 lb/A
C, D
3.
IR6141 Kiralaxyl 50WP
@ 1.6 lb/A
C, D
5.
REMEDIER 4WP
@ .2.2 lb/A
A, B
6. Kiralaxyl 50WP
@ 0.21 lbs/A
B
7.
@ 0.21 lbs/A
@ 2.2 lbs/A
A, B
A, B
8. Ridomil Gold 4EC
@ 0.2 gal/A
C, D
9. Kiralaxyl 50WP
@ 1.06 lbs/A
B, C, D
10. Kiralaxyl 50WP
@ 1.6 lbs/A
B, C, D
11. Kiralaxyl 50WP
@ 2.12 lbs/A
B, C
12. Ridomil Gold 4EC
@ 0.2 gal/A
B, C, D
Kiralaxyl 50WP
+ REMEDIER 2WP
____________________________________________________________________________________________
Field Application Schedule:
A-
7-days Before Transplanting
B-
At transplanting
C-
(4) weeks after transplanting
D-
(4) weeks before harvest
____________________________________________________________________________________________
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