A SUMMARY OF WEED CONTROL EXPERlENTS IN SWEET CORN ON TH
ORGANIC SOILS OF THE FLORIDA ~VERGLADES 1952-19L4.
Emil A. Wolf and V. L. Guzman
This is a Mimeographed Reprint from the P:roceedings
of the Eighth Annual Meeting of the So3hoA:rn Weed
Control Conference held in St. Petersbunrg, Florida
on January 17, 18 and 19, 1955.
A SUMMARY OF WEED CONTROL EXPERIMENTS IN SWEET CORN ON THE
ORGANIC SOILS OF THE FLORIDA EVERGLADES 1952-1954*
Emil A. Wolf and V. L. Guzman
University of Florida, Everglades Experiment Station
Belle Glade, Florida
For the past three or four years approximately 20,000 acres of
sweet corn have been grown on the peat soils of the Everglades for the
fresh market. At certain times, especially during the hot, rainy fall
months and warmer spring months weeds grow extremely rapidly and, in
particular, the troublesome common sticker weeds Amaranthus spinosus Le
Two, and sometimes three, hand hoeings are necessary to remove weeds be-
tween plants in the drilled rows. A summary of the results obtained from
twelve weed control experiments with herbicides conducted in peaty muck
soils from 1952 to 1954 inclusive is presented.
MATERIALS AND METHODS
Seven herbicides were tested to determine their effects on weed
growth and yields of sweet corn. The herbicides were as follows: (CMU)
3-p-chlorophenyl-l, l-dimethylurea, (DNOSBP) salt of dinitro orthosecond-
ary butyl-phenol, (CIPC) isopropyl N-3chlorophenyl carbamate, (MCP) 2-
methyl-4-chlorophenoxyacetic acid, (Oktone) octachlorocyclohexenone, (2,-I~)
amine, and (NIX) sodiumisopropylxanthate. All the herbicidal treatments
were applied in 30 gallons of water per acre and a 25 p.s.i. pressure wiuI
the exception of Oktone which was applied in 30 gallons of diseeel fuel.
Also in one experiment NIX was applied in 90 gallons of water at a pressuY '
of 40 p.osi. Amounts used are expressed in terms of active ingredients
per acre except for CMU which is commercial grade. Treatments were re-
plicated six times in each experiment. Plots were 30 feet long, consist-
ing of from one to 16 rows. The soil was rolled prior to pre-emergence
applications. Golden Security, loana, Illinois Golden #10, Calumet, and
Gold Rush varieties were used. Plants were thinned to approximately 12
inches apart in the row after notes were taken on stand. Mechanical cul-
tivation was carried out between the rows in all experiments except one
in which mechanical and complete chemical weeding were compared.
RESULTS AND DISCUSSION
PRE-EMERGENCE EXPERIMENTS: CMU at 2 pounds and DNOSBP at 12 pounds have
given the best control of weeds without reducing yields. In one experi-
ment yields of plots treated with herbicides were significantly greater
than from the check (Table 1). CIPC caused severe injury to the corn
* This work was made possible in part by grants from the B. F. Goodrich
Chemical Company and Columbia Southern Chemical Corporation.
plants. As a result, yields were significantly reduced. MCP at 2 pounds
gave excellent weed control but produced light bending and twisting of
the very young stems of the corn plants. Yields, however, were not re-
duced. Weed control with 2 pounds of 2,4-D and 2.5 pounds of Oktone was
only fair to poor. Similarly, NIX at 12 and 15 pounds was ineffective.
In these experiments it was noted that control of weeds was best when
the soil had been rolled after seeding and good moisture was present in
the upper portion of the soil.
Table 1. Total yields of marketable sweet corn ears in pounds per acre
from three weed control experiments conducted at Belle Glade,
Pre-emergence Rate/Acre Total Yields
treatments Lbs. Experiment la Experiment 2 Experiment 3
planted planted planted
Oct. 2, 1952 Feb. 18,1953 Feb. 20,1953
DNOSBP 12 5,685* 6,925 11,820
CMU 2.0 5,500* 6,935 12,L10
2,4-D 2 6,500 U11,10
CIPC 16 3,530*
MCP 2.0 5,260
NIX 15l 5,220
Check (hand hoed) 4,9h0 7,340 11,475
LSD. 0.5 395 N.S. N.S,
a. Differences in yield due to rate of treatment and interaction of
rates by treatment not significant; therefore, the yields are pre-
sented for the totals for both rates for all three varieties in the
* Significantly different from the check
1. Studies on time and method of 2,4-D applications on different sweet
corn varieties.- wo experiments were carried out in an attempt to de-
termine the effects of 0,75 pounds of 2,4-D amine salt applied at seven
stages of growth on four varieties of sweet corn. The first four treat-
ments made on plants 1 to 7.inchaa higs wre applied over the tops of the
plants and weeds; the other three were applied directionally to the base
of plants 15 to 18 inches tall, at incipient tasselling, and incipient
silking. The check was hand cultivated. There was a difference in tol-
erance of the varieties to treatment with 2,4-D. Golden Security was the
most susceptible to injury as measured by yields, followed closely by
Gold Rush. loana and Calumet varieties were most tolerant. The over-all
applications at the 1 to 2 and 2 to 3 inch stages, though causing some
slight bending and mild chlorosis of the plants, did not cause any perma-
nent injury with ary of the 4 varieties. Applications of 2,L-D at the 4
to 5 and 6 to 7 inch stages caused severe damage to the plants and the
yields. Directional applications to plants 15 inches and larger did not
produce any injury to the plants or yields. Excellent weed control (most-
ly sticker weeds) was obtained.
The second experiment, carried out in the spring of 1954, was
similar to the first except that only three varieties, Gold Rush, Golden
Security, and loana were used and over-all and directional applications
were made to all seven stages of growth. A split plot, randomized block
design was used with varieties the major treatments, methods of applica-
tion as sub-treatments, and stages as sub-sub-treatments. Again, with
the over-all application, 2,U-D symptoms on the corn plants increased in
severity from the one to seven inch stages and Gold Rush and Golden Se-
curity were more affected than loana. Treatments from 15 to 18 inches to in-
cipient tasseling showed light 2,U-D symptoms. Directional applications
of 2,4-D did not produce any symptoms except for the third and fourth appli-
cations, made when the plants were 4 to 7 inches high. Directional appli-
cations of 2,U-D generally produced better yields than the over-all type
of applications, mostly due to sharp reductions in yield from the over-all
treatments at the 4 to 5 and 6 to 7 inch stages (Table 2). These results
agree with those from the 1953 experiment except that a significant reduc-
tion in yield occurred in this experiment with over-all treatment at the
2 to 3 inch stage. With directional applications, only treatments at the
6 to 7 inch stage produced reduction in total yields of the three varie-
ties. Also, as in the 1953 experiment, there was a significant inter-
action between varieties and stage of treatment, showing there is a differ-
ent reaction of each variety to the same treatment at certain stages of
In addition to reductions in yield as indicated above, 2,4-D
caused significant reductions in ear length of the Gold Rush variety when
the plants were treated at all stages from 1 to 7 inches high (Table 3).
Length of ears of loana were significantly reduced only when the plants
were treated at the 6 to 7 inch stage, whereas with Golden Security ear
length was significantly reduced with all treatments made to plants 2 to
18 inches in height and length of unfilled ear tips was significantly
greater on ears from plants which received 2,4-D at 2 to 5 inches tall.
Length of unfilled ear tips of the other two varieties was unaffected.
Therefore, grade as well as yield of all three varieties was affected by
Table 2. Average yields of U. S. No. 1 or better sweet corn
pounds per sub-sub-plot of three varieties treated
pounds per acre of 2,U-D at Belle Glade, Florida.
planted March 10. 1954.
Stage Method of Treatment Average
Treated Over-all Dbirectional Stages
1-2" 8.52 9.00 8.76
2-3" 7.19* 10.26 8.73
4-5" 5.82* 9.44 7.63*
6-7" 4.83* 8.08* 6.46*
15-18" 8.91 9.64 9.28
Tasseling 8.51 9.72 9.12
Silking 9.39 9.92 9.66
Check 9.57 9.99 9.78
Average 7.84 9.50
LSD .05 for methods 0.85
for stages 1.38
for methods x stages 1.60
* Significantly different from the check
Table 3. Average length of U.S. No. 1 or better ears and unfilled tips
in inches of three sweet corn varieties as affected by the stages
of growth at which the corn plants were treated with 0.75 pounds
per acre of 2,4-D amine.
Stage Length of ears, inches Average
Treated Gold Rush loana Golden Security Stages
x stages .05 = 0.10
Length of unfilled
x states .05 = 0.12
* Significantly different from the check
I I I I I
the 2.-.D treatment but Gold Rush and Golden Security varieties were most
susceptible to injury.
2. Comparison of NIX and 2,4-D applied directio!ally. 2,,-D was applied
at 0.75 pounds in two experiments and at 10 pound in the third. NIX was
applied at 10 pounds in.all three experiments. In the first experiment
one application was made at lay-by. In the second, two applications were
made the first when the plants were from 12 to 15 inches in height and
the second as a spot treatment to weeds which had been missed by the first
application. In the third experiment, one application was made at tassel-
ing. In general, weed control with the 2,h-D and NIX was very good, with
2,9-D perhaps giving slightly better weed control. Some burning of the
lower leaves occurred with NIX; however, yields from both treatments were
equal to those from the checks. In the experiment where 0.75 pounds of
2,4-D was applied to Golden Security variety at tasseling, an apparent
beneficial hormonal effect was noted. A study of 10 ear samples from each
plot made separately and independently by three qualified observers indi-
cated unanimously that ears from the 2,4-D treated plots were more uni-
formly mature and about one day more advanced in maturity than those from
the check and NIX treated plots. Further study is needed on this obser-
vation before a definite conclusion can be drawn. However, if substan-
tiated this effect could be of considerable value to growers in helping
them to obtain uniform maturity for the one harvest operation and possibly
increase yield of second ears.
For best results with NIX the temperature should be 700 F or
above and no rain should occur for several hours.
3. Results with CMU. CMU was applied directionally and over-all on to
Golden Security plants 15 inches high at the rate of 2 pounds per acre
in one experiment. Weed control was excellent. A few corn plants re-
ceiving the over-all treatment showed light burning of the leaf
tips, but this disappeared in a few weeks. Yields from the treated plot,
were equal to that from the check plots,
4. Early post-emergence weed control with DNOSBP. Applications of DNOSBF
at 3.0 pounds were made on Golden Security variety at the two and four
leaf stages in the fall of 1954. One directional application of 2,4-D
was made at the lay-by stage. The check was mechanically cultivated and
hand weeded. Excellent-weed controlLas obtained with DNOSBP and 2,4-D
and-nothand weeding was necessary. Treatment of plants with DNOSBP at
the four leaf stage caused a marked check in growth, less suckering and
a reduction in mature plant size which were reflected by a two day delay
in maturity of ears and a significant reduction of yields (Table 4).
Treatment at the two leaf stage checked growth slightly and appeared to
reduce mature plant size on some replicates, but yield from plants treated
at this stage were equal to that from the check though delayed about one
day in maturity. Observations on another trial in which 3 pounds of DNOSBP
was applied just prior to the two leaf stage showed excellent weed control
for three to four weeks with no apparent injury to the plants and no cul-
tivation was necessary during that time. However, strong winds caused
severe lodging of the plants indicating that on the organic soils of the
Everglades the use of herbicides may not entirely eliminate mechanical
cultivation. It still may be necessary to move soil around the base of
the plants for mechanical support. Applications of 3 pounds of DNOSBP
at the "cigar" or rolled stage shows considerable promise especially
where annual grasses are a problem.
Table U. Total yields in pounds of marketable ears from sweet corn treat-
ed post-emergently with 3 pounds of DNOSBP per acre at two
stages compared with the untreated check. Treated September,
Treatment Total yield in
2 leaf stage 109
l leaf stage 80
LSD o05 21
5. Combined pre- and post-emergence experiments. Four experiments were
conducted to compare the effects of applying directional post-emergence
treatments of 2,U-D, NIX and CMU to plots which received pre-emergence
applications of various herbicides and a cultivated, hand-weeded check.
The 2,4-D amine was applied at the rate of 0.75 pounds in each of the
experiments, except for one in which it was applied at the one pound rate.
NIX was applied at a 10-pound rate in the experiment in which it was com-
pared with 2,4-D. In the experiment in which 2,4-D was applied at the IC-
pound rate conducted in the fall of 1952, heavy rains fell after the applJ.
cation of chemicals, damaging the corn plants severely, and no marketable
ears were produced. However, total weight of all ears produced from the
2,h-D treated sub-plots tended to be lower than the corresponding ones ii.
which various pre-emergence treatments had been made, indicating a poss-
ible toxic effect to the plants by the 1.0-pound rate under high tempera-
ture and excess rainfall conditions when applied following pre-emergence
treatments. In two experiments conducted under normal rainfall conditions
and designed to show any interaction between the pre- and post-emergence
treatments, no significant interactions occurred. Yields from plots re-
ceiving the combined pre- and post-emergence herbicidal treatments were
equal to those from the checks except for those receiving CIPC.
One experiment was conducted in the spring of 1954 to compare yields frca
plots treated entirely with herbicides, against yields from mechanically
cultivated, hand weeded plots. In this experiment, no mechanical culti-
vation was done on any of the herbicide treated plots. Treatments in this
experiment were (1) CMUJ as a pre-emergence, at 2 pounds, followed by a
directional application cf. 2 pounds of CMU as a post-emergence treatment;
(2) DNOSBP as a pre-emergence treatment at 12 pounds followed by direc-
tional application of 2,4-D at 0.75 pounds; and (3) a mechanically cul-
tivated, and hand weeded check. The post-emergence treatments were appli-
ed while the weeds were very small. The control of weeds with the herbi-
cidal treatments was excellent until harvest. Differences in yield were
not statistically significant; however, there was a trend toward better
yields from the herbicidal treated plots as reflected by the following
average yields in pounds per plot for the three treatments: Cultivated,
17.8: CMU pre- and post-, 20.0; and DNOSBP with 2,4-D, 23.8.
Twelve herbicide experiments were carried out with sweet corn
on the organic soils of the Florida Everglades from 1952 to 1954. Amounts
are expressed in the terms of active ingredient on a per acre basis ex-
cept for CMU which was commercial grade.
CMU at 2 pounds and DNOSBP at 12 pounds have given the best results with-
out reducing yields. Good moisture of the surface soil is necessary for
best weed control.
1. Studies of time and method of 2._-D application on different varieties.
Golden Security-7ad Gold- Rush vaieties were most suEseptible to injury by
0.75 pounds of 2,h-D amine. Ioana and Calumet were most tolerant. Yields
were severely reduced by over-all applications of 2,4-D at the 4 to 5 and
6 to 7 inch stages in both experiments. In one experiment, significant
reduction in yields also occurred when the plants were treated over-all
at the 2 to 3 inch stage. Directional applications caused a significant
reduction in yields only at the 6 to 7 inch stage. On the basis of the:3.
two tests, it appears that over-all applications of 2,4-D can be made sa.:-
ly on the sweet corn hybrids commonly grown in the Everglades area on pl ::..
up to 2 inches high. Although no reductions in yield or grade resulted
from over-all applications to plants from 15 inches high to silking, somr.
2,4-D symptoms were noted on these plants, therefore, it is suggested
that later treatments should be restricted to directional applications
after the corn reaches 12 to 15 inches tall.
2. Comparison of NIX and 2, -D applied directionally. Good post-emer-
gence weed control was obtained with both materials. Some burning of the
lower leaves occurred with NIX at 10 pounds but no significant reduction
in yield occurred.
3. Results with CMU. Directional and over-all applications of 2 pounds
of CMU on plants ~ inches tall gave good weed control without reducing
4. Early post-emergence with DNOSBP. Application of DNOSBP at 3 pounds
per acre as early post-emergence treatment when the corn plants were in
the two leaf stage gave very good weed control without affecting yields.
Treatments at the four leaf stage significantly reduced yields and delay-
ed maturity of the ears by approximately two days.
5. Combining pre- and post-emergence applications, Ccmbinations of pre-
and post-emergence applications of herbicides did ot affect yields except
in the case of CIPC and in the case of 2,4-D when applied at the one pound
rate under conditions of heavy rainfall and high temperatures. Pre-emergence
applications of DNOSBP at 12 pounds and CMU at 2 pounds with post-emergence
applications of 0.75 pounds of 2,4-D or NIX at 10pounds gave good to ex-
cellent weed control.
(1) Guzman, V. L. and E. A. Wolf. Effect of 2,L-D on Four Sweet Corn
Hybrids at Different Stages of Growth. 199 Proc. of the Florida
State Horticultural Society 66: 141-147.