TOXICOLOGY AND MODE OF ACTION - Agrochemical and Pesticide Safety - page 155

Dalapon, the sodium salt of dichloropropionic acid, acts similarly, mainly
against monocotyledons. Uptake is possible via the roots as well as the
leaves. Transport takes place in via both the xylem and phloem. The most
powerful action is obtained by spraying in the spring on young growing
plants. Deposition in the growth-active zones is possible as breakdown in the
plants occurs only very slowly. Little is known about the mechanism of ac-
tion, although the protein-precipitating properties, inhibition of pantothenic
acid synthesis, and other reactions contribute to it.

The very low toxicity of Dalapon to fish makes its application possible
in the elimination of reeds, sedges and rushes, etc., on and in drainage ditches,
but only after permission has been granted by the appropriate water authorities
and not in water protection areas. Table 5.9 lists several commercial products
containing aliphatic acids.

Glyphosate, due to its excellent systemic properties and broader spectrum
of ac ti vit y, ha s gr ea tly re pl ace d th e us e of he rb ici de s ba se d on TC A an d
Dalapon in previous years. Uptake occurs through the leaves, and transport
predominantly via the phloem, so that root or rhizome weeds are particularly
severely affected. Some days after its use, its effect is visible in brightening
of the leaves and inhibited growth; treated plants die after about 2-3 weeks.
Glyphosate blocks the synthesis of aromatic amino acids, which are particu-
larly important as precursors of proteins and secondary plant compounds.
Figure 5.8 shows a package of Roundup.

Glufosinate is a postemergent, nonselective, partially systemic contact
herbicide which acts on leaves as well as in the plant after uptake and trans-
port. Its action is delayed at lower temperatures. It causes inhibition of photo-
synthesis and interferes with amino acid metabolism of the plant, thereby
causing accumulation of NH 4 . The most important uses are in the control of
seed and root weeds in vineyards, and in fruit growing. A relatively quick deg-
radation with a half-life between 30 and 40 days occurs in the soil.

Table 5.9 Commercial products containing aliphatic acids.
Active Ingredient

Product—Trade Name

TCA (trichloroacetic acid) Konesta, NaTA

Dalapon Dalacide, Dalapon-Na, Gramevin, Unipon

Glyphosate Accord, Ranger, Rodeo, Roundup

Glufosinate Basta, Dash, Finale, Liberty

Toxicity

Several members of this family of herbicides are severely irritating and
can cause permanent damage to the eyes.