Title: Celery stalk rot fungicide trials.
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 Material Information
Title: Celery stalk rot fungicide trials.
Series Title: Celery stalk rot fungicide trials.
Physical Description: Serial
Language: English
Creator: Pieczarka, D. J.
Publisher: Agricultural Research and Education Center.
Place of Publication: Belle Glade, Fla.
Publication Date: 1979
 Record Information
Bibliographic ID: UF00076894
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 166140847

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S .Belle Glade AREC Research Report EV-1979-10 October 1979

Celery Stalk Rot Fungicide Trials Spring 9p f;?- ~l Fr. -1.
D. J. Pieczarka-/
PR 1 8 1980

Stalk rot, caused by the fungus Rhizoctonia solani, is an important disease af-
fecting celery grown in the Everglades agricultural area. Although spring weather

conditions are most favorable for stalk rot development, it can be a problem through-
out the growing season. The disease is characterized by the formation of rusty
colored sunken lesions on the base of maturing petioles. At harvest infected peti-
oles must be stripped from the stalks before packing for market, thus reducing grade
sizes and yields. As part of the ongoing celery crop management program at the AREC-
Belle Glade, fungicide evaluation trials for stalk rot control are being conducted
to determine the fungicide or fungicide combinations and rates that are best for con-
trolling the disease. This report summarizes test results from the spring 1979 con-
trol trial.


Materials and Methods

The fungicide control trials were conducted in a research plot located at the
AREC-Belle Glade. Seedlings of the celery variety 'Florida 2-14' were transplanted
0.6 ft. (.18 m) in rows 2 ft. (.61 m) apart on February 21, 1979, and the plots were
treated with Vegadex for weed control. Each treatment consisted of 22 ft. (6.7 m)
long rows replicated six times and arranged in a randomized complete block design.
The fungicides and formulated rates evaluated were: Manzate 200, 1.5 Ibs/A (1.68

kg/ha); Kocide 101, 1.5 Ibs/A (1.68 kg/ha); Difolatan 4F, 3 qts/A (7.0 1/ha); Bravo
500, 3.5 pts/A (4.1 1/ha); Benlate 50 MIP, 0.5 Ibs/A (.56 kg/ha); Rhodia RP 26019,
0.5 Ibs/A (.56 kg/ha); Kocide + Manzate 1.5 + 1.5 Ibs/A; Kocide + Bravo 1.5 Ibs +
3.5 pts/A; Kocide + Benlate 1.5 + 0.5 Ibs/A; Manzate + Benlate 1.5 + 0.5 Ibs/A; and


a Assistant Plant Pathologist, University of Florida, Agricultural Research and
Education Center, Belle Glade? Florida, 33430. .








Difolatan + Benlate, 3 qts. + 0.5 Ibs/A.
A total of 7 fungicide spray applications were made on a 4 to 5 day schedule
starting 6 weeks after transplanting and continued until 7 days before harvest
(early blight was not a problem during the first 6 weeks, thus no fungicides were
applied for controlling it). Insecticides were applied as needed based on scouting.
Treatments were applied using a motorized plot sprayer operated at 100 psi (6.9
bars) and delivering approximately 150 gallons/A (1404 1/ha). The sprayer was
equipped with two over-the-row nozzles and two drop nozzles per row. Plots were
harvested on May 16 and 17, and data collected were: 1) stalk weight before and
after stripping for stalk rot damage; 2) the number of petioles infected per plant
and 3) stalk sizes before and after stripping for stalk rot damage.


Results and Discussions

During this trial, conditions were very favorable for stalk rot development and
significant differences were observed between treatments. The effect of the various
fungicide treatments on reducing stalk rot losses is illustrated in Tables 1 and 2.
In the untreated control the mean stalk weight was reduced by 66% as a result of
stripping an average of eleven infected petioles per stalk. All fungicide treat-
ments reduced disease severity; however, Kocide + Bravo, Bravo, Difolatan and Difo-
latan + Benlate provided the best control contributing to satisfactory stalk sizes
(Table 2). The Difolatan + Benlate treatment is of particular interest because in
sweet corn trials this combination also was found to provide excellent control of
soil-borne pathogens causing preemergence and postemergence decay.
Presently, Difolatan is not labeled for use on celery but a residue tolerance

has been established. Furthermore, pencil striping, once thought to be aggrevated
by Difolatan, was not a problem in the Difolatan treatments.

At the present time, Bravo appears to be the best choice for controlling stalk
rot when this disease is a problem. In addition, Bravo also provides excellent con-
trol of celery early blight.







Table 1. Effect of fungicide treatments for controlling celery stalk rot.
Mean wt.bc-/ ean wt.c/
per stalk (Ibs) per stalk (Ibs) % wt. No. petiolesc/
Treatment Rate/A before stripping after stripping reduction stripped/stalk
Treatment

Control -- 1.99 e 0.57 f 66 a 10.6 a
Manzate 1.5 Ibs 2.39 abcd 1.10 e 54 b 8.6 b
Kocide 1.5 Ibs 2.22 cde 1.28 de 42 c 6.9 bc
Benlate 0.5 Ibs 2.21 de 1.28 de 42 c 6.9 bc
Rhodia RP 26019 0.5 Ibs 2.32 bcd 1.49 cd 36 cd 6.0 cd
Kocide + Manzate 1.5 + 1.5 Ibs 2.50 ab 1.64 bc 34 cd 5.6 cd
Manzate + Benlate 1.5 + 0.5 Ibs 2.49 ab 1.74 bc 30 d 5.3 cd
Kocide + Benlate 1.5 + 0.5 Ibs 2.52 ab 1.85 b 27 d 4.4 d
Kocide + Bravo 1.5 Ibs +:3.5 pts 2.64 a 2.29 a 14 e 2.2 e
Bravo 3.5 pts 2.47 abc 2.19 a 11 e 1.6 e
DifoqItan 3 qts. 2.44 abcd 2.13 a 10 e. 1.7 e
Difolatan + Benlate 3 qts + 3.5 pts 2.55 ab 2.42 a 5 e 0.7 e

a/ See materials and methods for metric rates.
b/ 1 .pound = 454.6 g.

c/ Stripping refers to Rhizoctonia infected petioles only.
d/ Values followed by the same letter do not differ significantly (P = 0.05) according to the Duncan's Multiple
Range Test.









Table 2. Celery yields before and after stripping Rhizoctonia infected petioles.

a/ Before and after Crates/A for each stalk size-b/
Treatment-/ stripping 2 2 3 4 6 8

Control Bd/ 0 150 457 288 36 0
A 0 0 0 47 47 31
Manzate B 202 361 322 164 31 0
A 16 50 52 132 88 74
Kocide B 187 386 353 132 26 4
A 62 62 135 171 93 58
Benlate B 93 349 384 202 16 0
A 47 50 125 148 93 86
Rhodia RP 26019 B 125 312 343 179 42 12
A 47 87 114 171 83 70
Kocide + ranzate B 203 449 343 125 10 0
A 47 137 239 132 62 47
Manzate + Benlate B 171 374 374 148 21 0
A 78 150 166 195 119 55
Kocide + Benlate B 156 449 343 140 16 0
A 31 249 249 218 78 23
Kocide + Bravo B 234 411 353 117 16 0
A 187 324 332 132 42 12
Bravo B 249 287 363 1.48 36 0
A 156 312 301 179 47] 12
Difolatan B 202 498 343 78 10 8
A 171 436 322 93 31 12
Difolatan + Benlate B 327 399 322 93 21 0
A 312 386 312 93 36 0
=1/


a- See Table 1 for rates.
b/ One acre = 2.47 hectare.

-/ Sizes refer to dozens of


stalks per crate.


d/ B = Before stripping Rhizoctonia infected petioles.
A = After stripping infected petioles.




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