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Bradenton AREC Research Report BRA1982-16 7 October, 1982
INFLUENCE OF VARIOUS ADJUVANTS ON EFFICAY '- ~ U.
OF AQUATIC WEED CONTROL WITH DIQUAT1 / iOV
J. P. Gilreath2 1P AS
Diquat is labeled for control of aquatic weeds in still bodies of watierbi--_''
such as irrigation ponds. Weed control can range from excellent to none,
depending on weed species and a number of other factors. One factor which can
have a pronounced effect on the activity of a herbicide is the use af an adjuvant.
Adjuvants vary in their mechanism of activation of herbicides. Some adjuvants are
simply wetting agents, (e.g., X-77) while others are drift or dispersion
retardants (e.g., Nalquatic). These are just two of several means of herbicide
enhancement by adjuvants. This research was conducted to evaluate the influence
of several adjuvants and a liquid copper material, Komeen, on the efficacy of
diquat for control of aquatic weeds in small ponds.
Materials and Methods
The various treatments listed in Table 1 were applied to 30 feet x 80 feet
ponds at the Florida Center of Biology near Palmetto, Florida on July 28, 1982.
Experimental design was randomized complete block (the ponds were laid out in
blocks) with 4 replications. Thus, each treatment plot was an individual pond.
The herbicide treatments were applied with a 20 gallon gasoline powered sprayer
fitted with an adjustable nozzle gun which was adjusted to a coarse stream.
Volume of application was 41 gallons per acre applied at 90 psi pressure. Weather
at application was partly cloudy, air temperature 940F and 80% relative humidity.
Wind was out of the NW at 5 mph. Pond water temperature was 90OF. The predominant
weed species were Chara spp. and Ludwigia repens. Also present in erratic popula-
tions were Najas spp. and Elodea spp. Due to the inconsistent occurrence of
these species, evaluations were only made for the main species. These evaluations
were made on August 2 and August 12, 1982 using a 0 to 10 visual rating scale
where 0 = no control and 10 = 100% control or complete kill.
Results and Discussion
Control of Chara spp., a submersed species, and Ludwigia repens, a shore
and shallow water plant, was significantly enhanced by all of the adjuvants
(Table 1). Five days after treatments were applied, the full extent of weed
control was evident in all plots as no increase in weed control was observed
af-terian additional 10 days. The best control of Chara spp. was affected by
combinationss of 3 gal/acre of diquat with either 4 gal/acre Komeen or 0.5 gal/
1Mention of a specific herbicide does not constitute or imply a recommendation
or endorsement by the author or the University of Florida.
2Assistant Professor of Horticulture (Weed Science).
acre X-77 plus 1% (v/v) Nalquatic, although these were not statistically superior
to diquat plus Nalquatic. Initial control of Ludwigia repens was 100% with diquat
plus X-77 and Nalquatic and 90% with diquat plus Komeen and diquat plus Nalquatic.
These three were significantly superior to diquat alone. Slight decreases in
control of Ludwigia repens by diquat plus Komeen were probably due to some slight
regrowth from populations above the treated water line.
Overall, the combination of diquat with X-77 and Nalquatic was numerically
superior but not significantly superior to the other adjuvant-herbicide
Table 1. Influence of various additives upon aquatic weed
diquat. Bradenton. FL. Summer. 1982.
controlz activity of
Rate August 2, 1982 August 12, 1982
Treatment (gal/A) Chara Ludwigia i Chara Ludwigia
Check -- O.Ocx 0.Oc O.Oc O.Oc
Diquat + Komeen 3 + 4 10.Oa 9.0a 10.Oa 8.7a
Diquat + X-77 + Nalquatic 3 + 0.5 + 1% 10.Oa 10.Oa 10.Oa 8.7a
Diquat + Nalquatic 3 + 1% 9.7a 9.0a 9.7a 9.0a
Diquat 3 5.2b 5.5b 5.7b 6.0b
ZWeed control rating on a 0 to 10 scale where 0 = no control and 10 = 100% control.
YChara spp., Ludwigia repens.
XMeans within columns followed by the same letter are not significantly different
at the 5% level, as determined by Duncan's new multiple range test.