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ERDC/CRREL SR-02-2
higher the organic content of soil, the higher the application rate that should be
used because the greater number of microbes in high-organic soil will break
down the chemical faster. Rainfall helps plants grow and can wash contact
herbicides off the plant and carry residuals into the soil and plant roots. Mixing
order, agitation, calibration of equipment, weather, and wind are all important
considerations for successfully applying chemicals. Temperature affects the rate
of plant growth and the absorption of residuals from the soil; high temperatures
speed up the degradation of chemicals.
Modes of action
Herbicides may be selective--affecting only certain plants, such as only
broadleaf weeds or annual grasses--or non-selective. Herbicides primarily affect
plant growth either systemically--by translocation within the plant--or by direct
contact with a specific part of the plant, such as foliage or roots. Some herbicides
have a residual effect in that they will persist for some time after application in-
stead of breaking down and becoming inert soon after application.
Growth regulator herbicides include
2,4-D (phenoxy acetic acid)
2,4-DP (phenoxy propionic acid)
dicamba
picolinic acid (picloram or triclopyr)
Photosynthetic inhibitors are
atrazine (Aatrex)
simazine (Princep)
prometon (Pramitol)
hexazinone (Velpar)
substituted urea (karmex/diuron)
substituted uracil (Hyvar XL)
Aromatic amino acid synthesis is inhibited by glyphosates (Roundup,
Rodeo, Accord, Dupont Glyphosate VMF).
Bud development is inhibited by fosamine (Krenite S).
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