Synthetic Auxin / Phenoxy Herbicide Group
A range of herbicides, collectively known as the phenoxy herbicides and synthetic auxins, affect the plant in a manner similar to endogenous auxin (IAA), a natural plant growth hormone. At low rates they can distort plant growth. At higher concentrations they affect cell walls and nucleic acid metabolism and inhibit cell division and growth, leading to plant death. They are effective in controlling a wide range of broad-leaf weeds.

    2,4-D                                  Synthetic Auxin     Group I
– (symptoms from plants exposed to 8 g a.i./ha at 12 nodes)            MORE

28 days after exposure

 
Dicamba                                     Synthetic Auxin      Group I
– (symptoms from plants exposed to 28 g a.i./ha at 11 nodes)             MORE

Fluroxypyr                                      Synthetic Auxin     Group I
– (symptoms from plants exposed to 36 g a.i./ha at 11 nodes)              MORE

Other Herbicides - Bleachers

A wide range of herbicides other than the phenoxys are commonly used in
agriculture and can cause mildto severe damage to cotton. Damaged plants
can display a wide range of symptoms, but as with the phenoxys, some
symptoms may be fairly general, over a number of herbicides. An example
is the Group C herbicides, which disrupt photosynthesis and at lower rates cause
 leaf bleaching. At higher rates, theycan cause necrosis and leaf death.

 
7 days after exposure

Other Herbicides -

Yellowers
The Group B herbicides disrupt amino acid synthesis, affecting protein biosynthesis.
Many of the Group Bherbicides are effective at very low rates for the control of broadleaf
and some grass weeds and are often used post-emergence in cereal crops. They can
have a longplant-back to cotton,especially on alkaline soils. The symptoms of
Group B damage caninclude bright yellowing of the growing tips.

25 days after exposure

27 days after exposure

27 days after exposure

25 days after exposure

Other Herbicides - Desiccants