Group Title: Central Florida Experiment Station mimeo report - Central Florida Research & Education Center ; CFES-68-3
Title: Weed control in spinach on the organic soils of Central Florida
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Permanent Link: http://ufdc.ufl.edu/UF00075850/00001
 Material Information
Title: Weed control in spinach on the organic soils of Central Florida
Series Title: Central Florida Experiment Station mimeo report - Central Florida Research & Education Center ; CFES-68-3
Physical Description: Book
Language: English
Creator: Scudder, W. T.
Affiliation: University of Florida -- Central Florida Experiment Station
Publisher: Central Florida Experiment Station, University of Florida
Publication Date: 1968
 Subjects
Spatial Coverage: Central Florida
 Record Information
Bibliographic ID: UF00075850
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 123193024

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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







HU i-E L ARY i

CENTRAL FLORIDA EXPERIMENT STATION APR 22 1968
Sanford, Florida
Mimeo Report CFES 68-3 ;j cFebiaEy?231ic968


WEED CONTROL IN SPINACH ON THE ORGANIC SOILS OF CENTRAL FLORIDA

W. T. Scudder, Associate Horticulturist

A selective chemical herbicide is needed for spinach grown on the organic
soils of Central Florida. Approximately 3000 acres of spinach are planted
annually on the Everglades peat and mucky peat soils of this area. At present,
there is no satisfactory herbicide available for commercial use with this crop.
While the plants are young, spinach is usually tilled by rotary cultivators to
eliminate weeds between the rows, but weeds in the rows often become serious.
If frost occurs, it will kill the less hardy species, but the occurrence of
frost is undependable. Further, populations of several frost-hardy weeds such
as curly dock (Rumex crispus), common chickweed (Stellaria media), bittercress
(Cardamine pennsylvanica), and burning nettle (Urtica urens) are building up
in the spinach producing areas.

At the present time, CDEC is the only herbicide registered for use in
spinach which provides effective weed control on these organic soils. Under
Central Florida conditions, however, this chemical is very phytotoxic. Its
use causes serious reductions in stand and stunting of growth. Studies to
select a satisfactory chemical herbicide were initiated at Zellwood in 1963.
Efficacy of treatments was determined by observing both weed control perform-
ance and tolerance of the crop to the herbicides. Selection of chemicals for
testing was based on previous organic soil screening trials and on work re-
ported by others.

During the past four years, 14 advanced trials testing herbicides for
spinach were conducted at Zellwood. Most of the experiments were planned
using a split-block design in the field. Of the two major blocks, one re-
ceived overhead irrigation shortly after the pre-emergence treatments were
applied. Each of these irrigation blocks contained three fully randomized
treatment replications. Standard plot size was one six-foot wide bed 22 feet
long, bearing four crop rows 12 inches apart. At harvest time, yields were
determined by recording the weight from 16 feet of the center two rows of
each plot.

The treatments were applied by broadcast spraying the chemicals in water
on the soil at 60 gallons per acre. The pre-plant incorporated herbicides
were mixed thoroughly into the soil two or three inches deep by using a Cultro
powered rotary tiller. The pre-emergence treatments were applied after seeding
and left on the soil surface.

Observational tolerance ratings were recorded for both stand and growth
of the crop, using a ten increment scale ranging from O to 10. A similar
scale was utilized for rating the effectiveness of weed control. Predominant
weed species were usually rated separately, although they occasionally were
grouped together and recorded as either broadleaf species or grasses. Besides


2CC copies








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the four weeds listed at the start of this paper, the plots contained other
hardy species including cudweed (Gnaphalium spathulatum) and prickly lettuce
(Lactuca scariola). In addition, the frost tender smooth pigweed (Amaranthus
hybridus) and common purslane (Portulaca oleracea) were plentiful in the check
plots prior to the first frost. There were few grasses.

Result data from several of these trials are listed in Tables 1 through 4.
The weed control ratings given are means for all species observed in the ex-
periment. Likewise, the crop tolerance data are averages of the ratings record-
ed for both stand and growth of the spinach.

Most of the herbicides tested during the 1963-64 season proved to be
toxic to the crop, although all had given indications of their potential use
for spinach in other trials. Among the better chemicals was Monsanto CP-13936
(methyl-o-nitrophenyl sulfide), but further development of this compound was
discontinued by the manufacturer in 1964. Likewise, trimeturon (Bayer 40557)
was shelved by the company after the winter 1964-65 trials. Diphenamid was
dropped from the later spinach experiments primarily because of inefficient
weed control on this organic soil.

Six chemicals, benefin, bensulide, EPTC, pebulate, trifluralin, and R-2063
(S-ethyl-N-cyclohexyl-N-ethyl thiocarbamate), were thoroughly incorporated into
the surface soil prior to planting. The use of EPTC was discontinued because
of serious crop injury which appeared in the second 1964-65 trial. Trifluralin
also has reduced spinach stand and growth occasionally. Weed control on this
organic soil by these soil incorporated chemicals generally has been erratic.
Of those tested, pebulate and R-2063 have given the best and most dependable
weed control.

Commencing with the fall 1964 experiments, Union Carbide 22463 (80%
3,4-dichlorobenzyl-NN'-methylcarbamate + 20% 2,3-dichlorobenzyl-N'-methylcarbamate)
and propachlor were applied as pre-emergence surface treatments. Use of both
of these chemicals resulted in excellent weed control. The effects with pro-
pachlor have varied considerably from test to test. In most cases, it has
produced excellent weed control, but it has occasionally given serious crop
injury when used at rates in excess of 3 pounds active ingredient per acre.
Both crop tolerance and weed control have been excellent following applications
of UC-22463 at either 4 or 6 pounds. As shown in the accompanying tables, the
recorded yields from plots treated with either of these herbicides equalled or
exceeded those produced in the untreated and cultivated check plots. Further
study with these two chemicals, and possibly with combinations using low rates
of each, is suggested.








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Table 1. Efficacy of several herbicides used for weed control in spinach
grown on organic soil at Zellwood during the winter of 1963-64.

Treatment Exp. I Exp, II
Rate CT Yield Yield
Chemical lb ai/a rating lb/plot lb/plot

CDEC 4 1.5 4.9 19.4
CP-13936 6 3.8 21.6 36.7
Pebulate 6 4.2 17.6 37.6
4 i 4.0 17.2 33.7
Trifluralin 4 i 2.2 4.9 8.4
Diphenamid 6 4.5 17.4 33.3
8 4.5 15.7 29.2
Amiben 3 2.0 6.2 12.4
Trimeturon 6 3.5 13.9 33.1
Prometone 3 0.0 0.0 2.9
Prometryne 1.5 1.2 5.5 9.50
Check 4.2 24.0 37.4
LSD (.05 level) 1.5 8.9 11.1

aTreatments followed by "i" were incorporated to a depth of 3/4 inch by
hand raking.
bprometone rate was reduced to 2 lb ai/a in Exp. II.

Prometryne rate was reduced to 1 lb ai/a in Exp. II.


Table 2. Efficacy of several herbicides used for weed control in spinach
grown on organic soil at Zellwood during the winter of 1964-65.

Treatment Experiment I Experiment II
Rate WC CT Yield WC CT Yield
Chemical lb ai/a rating rating lb/plot rating rating lb/plot

CDEC 4 8.7 5.0 18.3 9.0 6.5 23.0
Propachlor 4 9.3 8.4 20.8 9.8 8.2 26.5
UC-22463 6 9.0 9.6 22.0 9.7 9.0 28.2
UC-22463A 6 9.7 9.6 21.0 9.7 9.2 28.3
Trimeturon 6 8.8 9.0 21.6 8.5 8.9 26.6
Trifluralin 3 i 7.5 9.8 21.5 10.0 3.0 13.0
Pebulate 6 i 9.0 10.0 18.6 9.5 10.0 23.0
EPTC 6 i 8.0 8.8 19.4 9.0 6.0 16.8
Check 0.0 10.0 20.2 0.0 10.0 26.6
LSD (.05 level) 1.5 1.2 N.S. 1.0 0.8 2.7


aTreatments followed by "i" were incorporated
rotary tiller.


to a depth of 3 inches by






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Table 3. Efficacy of several herbicides used for weed
grown on organic soil at Zellwood during the


control in spinach
winter of 1965-66.


Treatment Exp. I Exp. II
Rate WC Yield Yield
Chemical lb ai/a rating lb/plot lb/plot

CDEC 3 5.4 11.8 9.2
UC-22463 6 9.6 19.7 14.0
Trifluralin l/2 i 3.2 14.2 13.0
2 i 3.6 10.0 9.2
Benefin 2 i 4.0 17.0 13.2
3 i 4.3 13.4 12.1
Pebulate 6 i 8.9 16.6 14.3
Bensulide 6 i 3.9 14.4 11.4
R-2063 6 i 7.9 15.7 12.5
Check 3.7 16.8 14.0
LSD (.05 level) 2.8 4.1 2.1

aTreatments followed by "i" were incorporated to a depth of 2 inches by
rotary tiller.


Table 4. Efficacy of several herbicides used for weed control in spinach
grown on organic soil at Zellwood during the winter of 1966-67.

Treatment Experiment I Experiment II
Rate WC CT Yield WC CT
Chemical lb ai/a rating rating lb/plot rating rating

CDEC 3 7.4 5.0 19.7 5.5 4.0
Propachlor 3 9.6 9.4 46.4 6.3 10.0
4 9.9 6.0 36.1 8.0 8.5
UC-22463 4 9.8 10.0 53.0 6.5 10.0
6 9.9 9.6 50.3 9.0 9.5
Trifluralin 1 i 3.8 10.0 4.3 9.7
12 i 5.2 10.0 5.0 9.0
Benefin 2 i 4.3 10.0 4.0 10.0
3 i 3.9 9.9 4.7 9.2
Pebulate 4 i 5.3 10.0 4.7 9.3
6 i 5.4 10.0 25.3 4.2 10.0
Bensulide 4 i 2.6 10.0 4.0 10.0
6 i 0.4 10.0 4.2 9.3
R-2063 4 i 3.5 10.0 5.0 9.7
6 i 6.5 10.0 30.0 6.8 10.0
Check 0.0 10.0 16.0 0.0 10.0
LSD (.05 level) 3.0 0.9 13.8 2.7 1.2


aTreatments followed by
rotary tiller.


"i" were incorporated to a depth of 3 inches by




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