gEMRBiCIfAL CONR&OL Op 1aDOB 6AnMAE
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V. L. Guzman
University of Florida, Everglades Experiment Station
Belle Glade, Florida.
In the sugar cane fields of the muck lands, 2,4-D has been used for
the control of weeds for several years. The use of this excellent herb-
icide year after year has brought about the partial eradication of sus-
ceptible weeds to 2,4-D. On the other hand, the number of resistant weed
species to 2,4-D has increased steadily. In many fields grasses, which
for the most part are not affected by 2,,-D, and pellitory weed (Pariet-
aria numularia Small), are becoming more predominant.
In order to find herbicides which will control these weeds in the
sugar cane fields, three progressive steps have been employed since 1952
as follows: 1. Herbicides and their combinations were screened in tests
non-replicated except in time. 2, The best herbicides were compared in
experiments with 1/50 acre plots replicated 5 times, 3. The best treat-
ments were tested in large size replicated experiments in which conmner-
cial equipment was used.
The object of this study was to compare the efficiency of herbicides
in controlling weeds, particularly grasses and pellitory weed, in exper-
iments of large size.
The experiments were conducted in plant cane. By the time of the
first post-emergence application, the cane fields had been cultivated a
few times with a light disc in the middles and mechanical scratchers in
the row. Herbicides were applied with a high clearance sprayer which
covered three rows 5 feet apart. Each plot consisted of 12 rows 644
feet long and 5 feet apart, or an area of 0.8 acre for the first experi-
ment in which Cl. 41-223 variety of cane was used. The six treatments of
this experiment were replicated four times. Herbicides were applied
three times. This new plant cane field had for many years been planted
to vegetables. During the summer months following harvest of the vege-
table crops, Alexander grass (Bracharia plantiginea (Link) Hitchc), and
other weeds grew profusely and the soil was badly infested by grass seeds.
Hence this field represents an extreme case of weed infestation. This
condition made it necessary to cultivate 23 times in order to keep the
check plots clean of weeds.
1/ This work was made possible by a Grant-inAid from United States
The plots of the second experiment consisted of 12 rows 5 feet
apart by 1291 feet long, or an area of 1.78 acres per plot. There were
five replications for each of the four treatments (Table 2). Herbicides
were applied twice. The field of the second experiment was fallow
plowed and disced 8 times in about six months prior to planting the
cane variety F 40-96. This field was relatively clean of weeds at
planting time although pellitory weed grew abundantly later.
The herbicides used in these experiments were: 2,4-dichlorophen-
oxyacetic acid (2,4-D), sodium trichloroacetate (TCA), 3-(p-chlorophenyl)-l,
l-dimethylurea (CMU) and triethanolamine and isopropanolamine salt of
dinitro ortho secondary butyl phenol (DNOSBP).
Results and Discussion
First experiment in a field heavily infested by grasses: The effect
of the chemicals on weeds, on the height and number of cane shoots, yields
of cane and 960 sugar is recorded in table 1. Best control of weeds,
mostly Alexander grass, was obtained by mechanical cultivation, next by
CIv and TCA mixture and finally by 2,4-D and TCA mixture. The heights of
cane shoots in the cultivated check plots were significantly less than
those in the herbicide treated plots, especially during the early stages
of growth. Three months before harvesting the differences in height had
disappeared. The check plants also had a significantly greater number of
shoots than plants of the herbicide treated plots. Breaking of cane
shoots by mechanical cultivation in the check plots appeared to enhance
the development of secondary shoots (1).
Table 1. Effect of applied herbicides on
of cane shoots, yields of cane,
No. 2,4-D Salts
weed control height and number
yields of 96 sugar and cost of
Shoots Yields in T/A gain y
Height No. Cane 96USugar checkO/
1 18.3 --- 1.9 -- 7 5186 96 39.6 4.49* $32.65
2 -- 4.5 41.9 -- 5 5628 106 43.4 4.93 72.02
3 12.5 -- 41.9 -- 6 5542 105 41.3 4.66 50.43
4 -- 5.2 41.9 -- 7 4830 97 34.0* 3.82* 3.89
5 -- -- 14.9 21.2 8 4513 101 39.1 4.61 -21.98
6 Cultivated (23 times) 9 2784* 129* 36.0* 4.28*
LSD .05 1164 20 2.88 0.30
1/ Scored on basis of no control 0, excellent control 10.
2/ Calculated on basis of cost of weed control, and yields of cane per
treatment at .8.00 a ton.
* Significantly different
(1) V.L.Guzman. Herbicidal Control of Ueeds in Sugar Cane Growing in Muck
Soils. The Soil Science Society of Florida Pro. 1954 (in print).
Cane yields were significantly increased over the check except
gf* treatment 4. It is difficult to account for the difference in
yield between treatments 4 and-2. Although the types of chemical and
application rates were similar, treatment 2 received only 2,14- on
the first application while treatment 4 received at the same time
2,4-D and TCA mixture. Later the case was reversed. Plots of treatment
4 also were accidentally scratched which may have placed the herbicides
in contact with the roots and thus injured the cane plants.
CMU residue analysis made by Grasselli Chemicals, E.I.duPont de
Nemours & Company, indicated that 11.51 percent of the 21.2 pounds of
CMU applied remained in the soil one year after the initial application.
This amount appeared not to be toxic to the sugar cane plants. It is
evident, however, that 21.2 pounds of CHU is too expensive to be used in
sugar cane, but experiments now in progress indicate that 2 pounds of
CMU mixed with 2 pounds of 2,4-D may be sufficient for general weed con-
Other experiments in progress indicate that 8 to 15 pounds of
Dalapon (sodium a, a-dichloropropionate) gives excellent control of
grasses, but the cane plants were severely stunted by these rates and
yield appears to be reduced.
Second experiment in a field lightly infested with weeds: Yields of
cane and 96" sugar were not reduced by the treatments (Table 2). Cane
of the herbicidal treated plots was slightly taller than that in the
cultivated plots, before lay-by time. The control of weeds on all the
treatments was excellent. The duration of the effect of the herbicides
on weeds was four, three and two months for treatments with CMU, TCA and
DNOSBP, respectively. However, 4 months after the original treatment
was applied, weeds (mostly pellitory weed) began to grow rapidly in most
of the treated plots.
The cost of weed control with herbicides (Table 2) was relatively
higher than costs using mechanical equipment.
Table 2. Herbicidal treatments and their effect on weed control, yields
of cane and 960 sugar.
Total herbicides Control Yields in tons/A Approximate
No. applied, lbs/A of weeds./ Cane 96Sugar cost per/A
1. TCA 26.8 mixed with 8 43.58 4.90 l14.76
2.a CMU 3.7 plus 2,4-D 2 9 43.55 4.98 13.20
3.a (iNOSBP) 8.6 plus 2,4-D -2 8 43.84 5.04 15.00
4. Cultivated check (5 tines) 9 43.00 4.75 2.25
LSD .05 NS NS
1/ Scored on a basis of no control = 0, excellent control = 10.
a 2,4-D was applied separately about 3 months after the first treatment.
Post-emergence weed control with 21 pounds of TCA mixed with
2.2 pounds of 2,4-D (applied twice) in a field of plant cane infested
heavily vdth grasses, appeared to be economically profitable due to
increased yields over the cultivated check plots.. In a field where
weed infestation was relatively light (mostly pellitory weed) the use
of herbicides was not better than the cultivated check plots. CMU
gave excellent control of pellitory weed.