GRASS CONTROL IN SUGAR CAME GROWN IN ORGANIC SOILS
V. L. Guzman
This report was orally presented to the Southern
Weed Conference at New Orleans, Louisiana on Janu-
ary 17. The research was conducted in cooperation
with United States Sugar Corporation and was support-
ed in part by a grant-in-aid from this Corporation.
EVERGLADES STATION IIMEO REPORT $56%.
Belle Glade, Florida
May 21, 1956
J(JUN 18 1956 2
- Gp 3 6,.
GRASS CONTROL IN SUGAR CANE GROWN
IN ORGANIC SOILS i/
University of Florida, Everglades Experiment Station
Belle Glade, Florida
Sodium Trichloroacetate (TCA) was the principal herbi'.
cide used for controlling grass weeds in sugar cane before
the discovery of Sodium a, a-dichloropropionate (Dalapon).
In preliminary tests conducted in 1953-U54, rates of 5 to
20 pounds of Dalapon in 30 and 60 gallons of water per acre
were used, Fifteen and 20 pounds of Dalapon per acre in-
Jured the sugar cane plants considerably and yields were
reduced. Rates of 5 to 10 pounds did n.t produce such se-
vere injury and grass control was commercially effective
under those conditions.
Among the various problems posed by this new herbicide
were: 1) what rates of Dalapon and what dilutions with
water should be employed in order to obtain the most effi-
cient control of grasses with the least injury to the cane
plant; and 2) what is the value of Dalapon as compared to
TCA alone or in combination with other herbicides. To ob-
tain partial answers to these problems, two experiments
were planned which for convenience in reference will be
numbered I and II.
In both experiments ratoons of the sugarcane variety
CL-1l-223 were used. Each plot consisted of 4 rows 5 feet
apart arranged in a split plot design with 5 and 6 repli-
cations respectively for experiments I and II. The her-
bicidal treatments were applied only once for experiment
I. This was done when the cane averaged 1.0 feet in
height (measured from the soil surface to the uppermost
visible dewlap of the leaf), and twice for experiment II
when the cane was 1.D and 2.0 feet tall as post-emergence
treatments to the cane plant and to the weeds. Rates of
herbicides are expressed as pounds of commercial grade
per acre, except for 2,4-D which was expressed as active
ingredient. The herbicides were applied in experiment I
V/ This work was made possible in part by grants from U.S.
Sugar Corporation, Clewiston. Florida*
on April 11, 1955, 66 days from the previous harvest,
while in experiment II the first application was made on
April L, and the second on May 23, 84 and 134 days re-
spectively from the previous harvest. The fieldfor Ex-
periment I was lightly infested with grasses. In this
field a blanket application of 2,4-D for the control of
broadleaf weeds was made several days prior to the use of
the Dalapon treatments. The field for experiment II was
heavily infested with Alexander grass (Brachiaria planti-
genea (Link) Hitchc.). At the time of the first herbi-
cidal application the grass in this field was 10 inches
high. For the past two years this field had been used for
preliminary tests with various herbicides and no mechani-
cal cultivation had been used, In these tests no cultiva-
tion was employed except in the check plots which were
rototilled twice in both experiments, in addition to one
hand hoeing in experiment I and two hand hoeings in experi-
Results and Discussion
Objective: To determine the effects of e.O. 7., and 10 pounds
of Dalapon in combination with 30, 60, 90, and 120 gallons
of water per acre on the sugar cane plant and grass control.
The major treatments were rates of Dalapon and the sub-
treatments amount of dilution with water. The treatments and
certain partial results obtained are reported in Table 1.
Control of grasses was effective with 5, 7.5, and 10 pounds
of Dalapon. More rapid kill of grasses was obtained with 10
pounds than with 7.5; likewise it was more rapid with 7.5
than with 5 pounds. However, one month after treatment dif-
ferences in grass kill were difficult to detect. The
amounts of water used affected the control of the grasses.
The 60 to 90 gallon rates appeared slightly more effective
than either 30 or 120 gallons. A similar trend in phyto-
toxicity was noticeable on the cane plants. No explanation
was found for the decrease in herbicidal action of Dalapon
when using 30 and 120 gallons of water per acre. Perhaps
30 gallons of water per acre is not enough for proper wet-
ting and coverage of the grass weeds while 120 is too much
and a certain amount of Dalapon is lost by runoff.
Injury by stunting and light burning of the cane leaves
was more conspicuous with 10 pounds than with 7.5 pounds of
Dalapon per acre. Five pounds of Dalapon did not seem to
affect the cane plants in any material way. Yields of cane
and of 960 sugar are given in Tables 1 and 2. No significant
differences in yield occurred due either to rates of Dala-
pon applied or to the amounts of water used. These re-
sults seem to indicate that one application of Dalapon
per season at the rate of 5 to 10 pounds per acre did not
affect the yield of the sugar cane plant.
Table 1. The effect of rate and concentration of Dalapon
on grass control and on the growth and yield of
sugar cane. Harvest: December 21, 1955*
Cane 96 Sugar
Zero to ten rating with ten indicating full control.
Readings taken 20 days after the herbigidal treatments
Zero, no damage; ten, severe stunting and burning of
Fifteen days after hand weeding the check plots.
Table 2, Yield of cane and of 960 sugar in response to
treatment with three rates of Dalapon in com-
bination with four different concentrations
in water. Harvests December 21, 1955.
Main Treatments Caen Tons/A 96 ar
Dalapon, Lbs/A. //A*
5.0 61.9 7923
7.5 59.9 7680
30.0 5$7. 7232
F. value N.S. N.S,
0 60.1 7601
30 59;3 7488
60 59.6 7579
90 59.0 7544
120 60.9 78i6-
F. value N.S. N.S,
j/ 85% commercial formulation.
Objective. To compare the effects of Dalapon and TCA alone and
in mixtures with other herbicides on the cane plant and on the
control of' grass weeds The results are given in Tables 3 and'
2. The double rates of 10 pounds of Dalapon and 20 pounds of
TCA are about the maximum amounts which was thought could be
used on sugar cane per application. Dalapon at rates of 5 and
10 pounds was superior for grass control to 10 and 20 pounds
of TCA when applied as post-emergence to the grasses. Twenty
pounds of TCA did not control the large grasses under the
conditions of this experiment and the 10 pound rate proved
less effective than the 20. The mixtures of Dalapon with Kar-
rex W and/or with 2,4-D gave better control of all types of
weeds than the corresponding mixtures with TCA. The best
combination appeared to be 5 pounds of Dalapon with 1.5 pounds
of 2,.4-D. Mixtures of Dalapon or TCA with Karmex W, either
with or without 2, -D, seemed to have a strong contact effect
on the cane and weeds. However, if not completely killed,
grasses and weeds tended to recover in about a month and a half.
Dalapon at the 5 pound rate produced slightly better kill of
grasses than an equal rate of Dalapon mixed with 2,2-D. How-
ever, this combination is quite effective for killing grasses
and other weeds.
Injury to the cane was most severe in mixtures which con-
tained Karmex W and more so with Dalapon than with TCA.
The check in growth and the light burning of leaf tips of
the cane plant were noticeable up to one month after treat-
ment, The degree of injury of the cane plants by the her-
bicidal treatments was to a large extent reflected by a
proportional reduction in the yield of the cane (Table 3.;
Yields were reduced with Dalapon and TCA (Tables 3
and 4 ). The interaction of Dalapon and TCA is also signi-
ficant (Table 3). This probably indicates that Dalapon and
TCA in some of the corresponding mixtures used had different
effects on the sugar cane-plant. The over-all effect of
Dalapon and TCA on yields, however, is similar (Table L,
Table 3. Amounts of chemicals per treatment (applied twice)
and their effect on weed control, injury to the
cane plant and yields of cane and of 96 sugar per
acre. Harvest: November 22, 1955.
Dal. + Karmex W
Dal. + 2,li-D
K.W. f 2,1
Index ;/ Index 2
for for To-
Lbs/A I/ Grass C. tal WoCa
10 9 4
5 8 4
5. + 2 7 7
5+1.5 8 9
4-D 5+2+1.4 7 8
0 2/ 0
20 6 4
10 & 3
10 + 2 5 6
3D10 + 1.5 6
-D l0041.5 5 6
to- ane Sugar
t 29.7 5481
1 0.8 7544
3 37.9 6952
1 4s2.9 0331
h 34.1 6230
0 5.0 8950
1 39*8 7951
0 39.6 8120
2 3L.6 6660
1 36.8 7298
2 32.2 5969
LSD .05 for interaction
LSD .01 "
Rates per application. Double the rates to obtain the total
Zero, no control; 10, full control.
Before, hand weeding.
Zero, no injury; 10, severe stunting and burning of leaves.
Table 4. Yields of cane and of 960 sugar per acre as in-
fluenced by Dalapon and TCA treatments alone and
in cixtures'with other herbicides. Harvest:
November 22, 1955.
Cane Tons/A. Sugar Lbs/A.
Combined effect of Dalapon
and TCA (sub-treatments)
1- Check (cultivated)
4- + Kjrmex W.
5- + 2,s4D
6- -% KarmexW +' 2,4-D
The returns after deducting the cost of weed control are
given in Table 5. Although significant reduction in yield was
obtained due to use of the herbicides, the cost of cultivation
and hoeing was so high that some of the herbicidal treatments
gave economical advantage over the check.
Table 5. Cost of weed control and returns obtained in relation
to yield of 960 sugar.
Check (cultivated and hoed) !3827
Dalapon 10 lbse 327;2
Dalapon 5 lbs. 46.o4
Dalapon + K;W, .15I1
Dalapon + 2,4-D L97.*
Dalapon f K.W. + 2,2A-D 383.9
TCA: 20 Ibs. 474.7
TCA: 10 Ibs. 484.8
TCA + KLW. 397.6
TCA 4 2,4-D 43.7
TCA + K.W. A 2,L4D 56.3
Obtained by multiplying $5.97 cwt by y
Two tillivations and two hand hoeingse
Yields were not affected by one application of 10 pounds
of Dalapon in experiment I. In experiment II, however, when
10 pounds were applied in two treatments of 5 pounds each,
yields were decreased. In experiment I, rain fell two and three
days after application of the treatments, whereas in experiment
II 9 days elapsed before rainfall, after both the first and
second applications of the herbicides (Table 6). Since'Dalapon
can be washed out by rain from the leaves of the plants, it is
possible that the cane in experiment II absorbed more Dalapon
through the leaves than those of experiment I. The cane in ex-
periment II was one month older than in experiment I and there-
fore had more leaf area, which may have contributed to more
absorption of Dalapon. Furthermore, soil moisture was adequate
for rapid growth of the cane, and the relatively high tempera-
tures present after treatment (T 900F, range 670 780 F.-10
days average) may have resulted in the absorption of Dalapon by
the rapidly growing cane plant in toxic amount. Consequently,
the timing for the second application or the time interval be-
tween the first and second treatment may have been critical in
relation to the rate of growth of the cane plants.
Table 6. Rainfall in relation to the dates of application of
herbicides and previous harvest in fields for ex-
periments I and II conducted during 1955.
Apr. 2, 1955
Experiment I *
February 8-11, 1955
Apr. 11, 1955
January 10, 1975
Apr. f; 1955
May 24. 1955
pr.- Herb* applied
iy 8 1.31
ay 14 .06
ay 17; 1.14
ay 18, *07
ay 19; .43
ay 20; .27
ly 2,4 Herb. applied
me 2,' .47
me 10 .54
me 11, 2.42
In experiments conducted in the past (1,2 and 3) TCA pro-
duced yields similar to or better than the cultivated check.
However, in experiment II, cane and sugar production were decreas-
ed considerably by the use of TCA. The decrease in yield
could be attributed in part to the lack of adequate control
of grasses, probably due to the lack of rain soon after
the application of TCA.
In experiment I, yields of cane and of 960 sugar were not
affected by one application of 5$0, 7.5, and 10.0 pounds of
Dalapon in all possible combinations with 30, 60, 90 and 120
gallons of water per acre. Control of grass weeds was effective
with all rates of Dalapon used. Sixty and 90 gallons of water
per acre appeared to be slightly more effective than 30 or 120
In experiment It yields of cane and of 960 sugar were re-
duced by two applications of Dalapon or TCA either alone or in
combination with Karmex W, 2,4-D or both. Control of grasses
was more effective with Dalapon than with TCA. Best control of
grasses and other weeds was obtained with 5 pounds of Dalapon
in a mixture with 1.5 pounds of 2, -D amine. Time of the se-
cond herbicidal application in relation to the rate of growth
of the cane plant is perhaps an important factor in determin-
ing yield reduction of both cane and sugar. Certainly it is a
consideration that should be investigated further.
Acknowledgments are due Messrs. J.W, Doty, B.W. Hundertmark,
P.S. Francis and I.M. Jackson for valuable assistance rendered
in conducting these experiments.
Guzman, V.L., Herbicfdal control of weeds in sugar cane grow-
ing in muck soil. Sotl Sci. Soc. of Florida Proc. Vol. XIV,
.____ Herbicidal control of weeds in sugar cane on or-
ganic soils. Proc. Eighth Annual Meeting of S.W.C. 203-206,
_______ ., Herbididal control of weeds in sugar cane grow-
ing in muck soil. Soil Sci. Soc. of Florida Proco Vol. XV,
1955. In Press.