Everglades Station Mimeo Report 60-22 May 10, 1960
THE EFFECT OF DALAPON ON SUGARCANE GROWTH AND YIELD: Preliminary Report
J. R. Orsenigo
SUMMARY Dalapon is used to a limited extent to control grass weeds in sugar-
cane in Florida. Annual grass seedlings have been controlled effectively by
split (2 or 3) applications of dalapon totaling 10 Ib/A per season. Cane growth
and yield responses to dalapon application have not been consistent. Recent
experiments have evaluated some of the factors associated with injury to sugar-
cane. Significant reductions in sugarcane growth rate and total growth, % yield
of 960 sugar, and tons per acre of cane and of 960 sugar have been associated
with dalapon treatments. Injury was greatest under the following spraying condi-
tions: Application broadcast overall to the foliage; 4 Ib/A per application; or
three applications. Less injury was associated with: directional spraying;
3 Ib/A per application; or two applications. Two directional applications of
3 Ib/A had no influence on cane growth or yield. Further evaluation is anticipa-
The herbicide dalapon ("Dowpon", sodium salt of 2,2-dichloropropionic acid)
is effective in controlling small grass weed seedlings in sugarcane and is used
commercially to a limited extent in Florida. The response of sugarcane to dala-
pon has been investigated in recent years by the Everglades Experiment Station
assisted by a grant-in-aid from the United States Sugar Corporation. Trials
prior to 1956 were conducted by Dr. V. L. Guzman; since 1957 trials have been
conducted by the author and supported additionally by field, laboratory and
analytical facilities of the above Corporation.
Sugarcane has been injured by single sprays of high rates of dalapon while
single, low-rate sprays have not controlled annual grass weeds successfully.
Cane injury from dalapon was reduced by using several repeated low-rate sprays.
In earlier trials, yield of sugarcane did not differ between overall or direc-
tional dalapon sprays. However, cane yields were reduced by applying dalapon
late in the season (May).
Dalapon applied soon after harvest when weeds were small (January-March)
was more effective in control of grass weeds than later applications to larger
grasses (April-May). One dalapon spray controlled small grass seedlings but two
sprays were required for larger grasses. Seedlings of annual grasses have been
controlled effectively by 10 Ib/A/season of dalapon split into two or three
An experiment was initiated in 1956 to study the rate and number of dalapon
applications associated with optimal grass weed control and minimal sugarcane
injury. In the first crop harvested, yields of sugarcane and of 96 sugar did
not differ significantly among the various dalapon treatments and the mechani-
cally-weeded control. Identical treatments were repeated on the same plots
in the second year of the experiment and practical grass weed control was
obtained with two 5 lb/A or three 3, 4, or 5 lb/A treatments. Traces of cane
injury were evident for two months after a single 5 Ib/A spray and for several
months after two or three 4 or 5 Ib/A sprays. Although tons of sugarcane
per acre did not differ significantly, yield of 960 sugar was reduced signifi-
cantly below the check by all dalapon treatments.
Additional research was prompted by the preceding divergent results.
Dalapon was applied two or three times at 3 or 4 Ib/A either as broadcast-over-
all or directional sprays to plant cane. The interval between repeat treatments
was one month. The combinations applied are illustrated more clearly in Table
1 which also presents growth and yield data.
Dalapon treatment caused significant differences in sugarcane growth-rate
and total growth, V yield of 96 sugar, tons of cane per acre and tons of 960
sugar per acre. The most severe reductions were associated with the following
dalapon usages: overall spraying, 4 Ib/A/per application, three sprays. Lesser
reductions accompanied directional application, 3 Ib/A/per application, and two
sprays. Two sprays of 3 lb/A applied directionally did not differ from the
cultivated control in growth or yield. This experiment is being continued to
ascertain cane regrowth and recovery. Additional experiments are planned to
evaluate completely the response of sugarcane to dalapon.
Safety in the use of dalapon in sugarcane appears to be related directly
to proper management in application. The following suggestions are offered for
effective, safe use of dalapon:
Apply to young grass weeds as early as practicable in growth of both
weeds and cane.
Avoid wetting cane foliage with dalapon sprays; use directional equipment.
Do not use rates higher than 3.5 lb/A of commercial "Dowpon" per spraying
nor make more than two applications per crop season.
Table 1. Growth and yield data for sugarcane response to dalapon applications. Variety Cl. 41-223.
Method Rate Number
4 months 9 months
j Yield 960 Sugar
Tons per Acre
Sugarcane 96V Sugar
Overall 3 Ib/A
Directed 3 ib/A
f" 4 lb/A
1. Measured to the youngest visible dewlap
of marked canes.
These data are for 4 and 8 months after the first
NB. Overall sprays wet at least 90 per cent of the cane foliage; directional sprays did not wet more than 15
per cent of the foliage. Rates of application correspond to 3.5 and 4.7 lb/A, respectively, of commercial
product, "Dowpon". Yield and analytical determinations by the Research Department of the United States