persist in water for periods ranging from 2 to 46 days (Hiltibran 1962,
1970,
and Chesters 1975,
and Lee 1976, Serns 1977).
2,4-D
The herbicide 2,4-D is a
acid.
It is available as the
The herbicide must be absorbed by plant tissue
acid or in salt or ester form.
The sodium and potassium salts penetrate poorly, the ammonia
to be effective.
and amine Salts somewhat better, and the hydrolyzed ester (e.g., butoxyethanol
ester, BEE) is readily absorbed and translocated.
The action of 2,4-D in the
plant is unclear except that it behaves like an auxin (Loos 1975, Westerdahl
and Hall 1983).
The herbicide 2,4-D is particularly effective against
(1982) considers 2,4-D to be the most effective and eco-
Doses of 20 to 40 kg acid equivalent/ha,
nomical treatment of this plant.
DMA (dimethylamine salt) or 2,4-D BEE, are usual.
normally of
Bates, and Stanley (1978) have reported that 2,4-D is effective against
foil, particularly when combined with water level drawdown.
Adams (1983) cau-
tions that root contact is essential for long-term milfoil control and that
the use of granular formulations can be ineffective if the pellets become
If an early season application is not
trapped and suspended in the foliage.
possible, then the use of a harvester prior to application will allow the her-
Adams (1983) also recommends that the
bicide good contact with the roots.
normal dose of 22 kg active ingredient/ha of the granular formulation of
be doubled for dense infestations in deep water
BEE
Otherwise,
dilution will
m) where there is a high water turnover rate.
be too great to produce control.
Depending on the dose and degree of infestation prior to treatment,
2,4-D remains effective against milfoil for at least the season of applica-
and Wile 1979; Getsinger,
tion, and often longer (Smith 1971; Aiken,
Davis, and Brinson 1982; Adams 1983).
Other plants may not be adequately con-
Controlled-release formulations may provide even longer control of
trolled.
Pierce (1960) found that species of
milfoil (Van, Steward, and Jones 1986).
returned in 1 month and grew heavily, while
was
Adams
also reported an invasion of
unaffected at doses up to 6 ppm.
Potamogeton after elimination of milfoil.
Although 2,4-D appears to have a short persistence in the water column,
it can be detected in mud samples for months (Faust and Aly 1961;; Smith and
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