POST-EMERGNCE GRASS AND TEED CONTROL IN SUGAR CANE
V, Lq G1zman
This report was presented before the Southern Weed
Conference at Augusta, Georgia in January 1957 and
is published in the Proceeding Tenth Annual Meeting
of this organization. The research was conducted
in cooperation with United States Sugar Corporation
and was supported in part by a grant-in-aid from
EVERGLADES STATION MIMED REPORT 57-16
Belle Glade, Florida
March 12, 1957
Table 1. Rates of herbicides, dates of application and their effect ...
on the cane plant and weed control.
Herbicides in Lbs/A
April 7 May 31
1.TCA+2,4-D 15 + 1.5 15 + 1.5
2.Karmex W+Dowpon 2 + 5 2 + 3
3.Dowpon+2,4-D 5 + 1.5 3 + 1.5
b.Downpon 5.0 3.0
$.Dowpon 10.0 3.0
6.Karmex W+C62L9 2 + 5 2 + 7.5
7.Check (Hand weeded)
I/ Zero, no injury; 5, severe injury
SZero, no control; 10, complete control
Total Effect on
Lbs/A tho cane Y/
pon. Thud in the TCA plots large grasses grew after a few weeks. Plots
treated with Dowpon alone were free of grasses but large sticker and
purslane weeds were present. It was necessary to use supplAmentary hand
weeding in plots treated with Dowpon alone. Karmex U, whether in combination
with Dowpon or C6249, gave fair control of both grasses ana weeds.
The leaves of the cane plants were burned by TCA and to a lessor degree
by the mixture of Karmex W and Lowpmn. In the case of TCA, however, cane
leaves grew rapidly and appeared normal within three weeks. The cane plants
treated with Karmex i plus Dowpon and with 13 pounds of Dowpon remained stunt-
ed and slightly chlorotic for about a month and a half. Cane treated with
Karmex I and C6249 did nct chow symptoms as severe as in the case of the
combinations of Karmex W andDowpon,
Table 2. Yield per acre of cane and 960 sugar as affected by post-emergence
1. TCA + 2,4-D
2. Karmex U + Dowpon
3. Dowpon + 2,4-D
6. Karmex !I + C6249
30 + 3
4 + 12.5
alone or in
of cane and 960 sugar were not affected by eight pounds of Dowpon
combination with 2,4-D amine salt (Table 2). Other treatments
a significant yield reduction of both cane and 96 sugar.
Considering the over-all performance of these herbicides on grass control
and on the cane, the use of eight pounds per season of Dowpon alone or in
combination with 2,4-D seemed to give the best control with .los-: injury to v
.the cane plants.
Table 3. Cost of weed control and gain or loss obtained by the use of
Cost of weed Returns minus cost Gain or loss
control/A of Weed Control/A 3/ over Check/A
1. TCA+ 2,4-D 813.50 $671.8.. -08.60
2. Karmex ~! + Dowpon 21.60 623.16 -133.29
3. Dowpon + 2,4-D 9.10 774.16 +17.71
4. Dowpon + Hand weeding 12.20 785.39 +28.94
5. DaIpon + 16.70 663.88 92.57
6. C6249 + Karmex W 25.40 573.98 -182.47
7, Cultivated Check 28.00 756.45
At ')$.00/A for pulling a few weeds
Assuming similar price as Dowpon
At ':.97 cwt.
Table 3 shows the loss or gain obtained with each herbicide for grass
and weed control as compared with mechanical weeding in relation to the yields.
Best results were found with the use of Dowpon at the rate of eight pournds
per season, either with or without 2,4-D,which gave a gain of :"17.71. and
.28.9L, respectively, over the check. The combination of Dowpon and 2, -D
controlled both small grasses and other weeds quite effectively.
It has been shown (1,2) that TCA plus 2,h-D gave good control of grasses
and weeds and in most cases cane yields were as good or better than the check,
In one instance, however, 960 sugar was reduced (1) and in another case both
cane and sugar yields were reduced when TCA was used alone or in mixtures with
other herbicides (3). In the present experiment TCA applications decreased
the yields of cane and sugar. This could be due to the failure of TCA to
control grasses effectively and thus in part to weed competition.
Dowpon at eight pounds per acre gave excellent results in this experi-
ment then used alone or with other herbicides for controlling grasses. Yields
were not affected by the use of eight pounds of Dowpon per season. Two
applications of five pounds of Dowpon each, decreased the yield of the cane;
however, in another experiment one application of 10 pounds of Dowpon did
not affect yields (3). In the experiment reported here two applications with
a total of eight pounds also did not affect yields. Mhe same cane variety
was used in these tests and date of application were approximately the same.
Where yield reduction occurred, Dowpon was applied on April 5 and May 24 (3).
'Jhere yields were unaffected, spraying was done on April 7 and May 31 on
cane one month younger than in the first case. These results might be inter-
preted to indicate that the stage of growth of the cane at the time of the
application could be important. It is possible also that the margin of safety
for the amounts of Dowpon to be used on the cane is relatively narrow. Hore
work is needed along this line.
Mixtures of Karmex U with Dowpon or C6249 resulted in yield reduction,
which is in agreement with results already reported (3). This may indicate
that mixtures of these chemicals are more potent on the cane than either
herbicide used alone. Perhaps lower rates of the herbicides would not harm
the cane; however, it seems likely that the weed killing action could be
impaired. It is doubtful, therefore, that mixtures of Karmex 1. with Dowpon
or C6249 would be of much practical value.
The grass killing compound C6249 appeared visually to be less toxic to
cane than Dowpon, but in spite of this appearance yields were more severely
reduced by the C6249. It was less effective than.Dowpon for killing grass,
thus further investigation seems unnecessary.
The most promising herbicidal mixture for killing grasses and other
weeds appeared to be Dowpon plus 2,4-D. Plots treated with these mixtures
were the cleanest and yields of cane and sugar were unaffected.
Various herbicides were compared for their grass killing properties
Dowpon at rates of three to five pounds seemed effective for controll-
ing crowfoot and crabgrass but was ineffective against other weeds. A mixture
of three to five pounds of Dowpon with 1.5 pounds of 2,4-D amine salt was the
most effective formulation for grass and weed control and caused no harmful
effects on yields of cane and 960 sugar.
1. Guzman, V. L. 1954 Herbicidal control of weeds in sugar cane growing
in muck soils. The Soil Science Society of Florida. Proc.Vol..XIV,1U-121..
2. 1955 Heroicidal control of weeds in sugar care growing in
muck soils. The Soil Science Society of Florida. Proc.VoXV., .3-59-.
3. 1956 Grass control of sugar cane growing in organic soils.
Everglades Station I'imeo Report 56-14. Presented orally to the Southern
Ueed Conference at New Orleans, Louisiana on January 17, 1956.
Acknowledgment is due Messrs.. 3. T. Hundertmark and P. S Francis of the
United States Sugar Corporation for valuable help in conducting this ex-
periment and Drs. J. N. Simons and H. !I. Burdine for reviewing the manuscript,