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Round Up / glyphosate



Chemical Structure

Chemical Name:

N-(phosphonomethyl)glycine.

Chemical Family:

Amino acids.

WSSA Resistance Group:

4

Crop/non-crop registration:

Non-selective (except in ROUND UP READY transgenic crops such as soybeans, canola, cotton, corn, sugarbeets), used for killing established weeds before crop planting and after harvest ('burndown'), brush and tree control in revegetation areas, right-of ways, turf renovation

Sensitive weeds:

Non-selective, but annual and perennial grasses most affected; perennial weeds controlled include: quackgrass, perennial sow-thistle, field bindweed, poison ivy, common milkweed, yellow nutsedge; also controls woody brush species such as birch, alder, poplar, wild raspberry, willow and maple.

Application method:

PREPLANT, POST, and POST-HARVEST.

Absorption & Translocation:

Absorbed through foliage (especially the isopropylamine salt of glyphosate in the presence of a surfactant) and translocated via symplast throughout the plant; accumulates in underground tissues, immature leaves, and meristems (i.e. carbohydrate sinks); glyphosate may interfere with its own translocation from treated leaves by interfering with carbon partitioning and metabolism.

Mode of Action:

Inhibition of the shikimic acid pathway and inhibition of S-aminolevulinic acid synthesis.

Metabolic pathway inhibited:

Inhibits 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase which produces EPSP from shikimate-3-phosphate and phosphoenolpyruvate in the shikimic acid pathway; EPSP inhibition leads to depletion of the aromatic amino acids tryptophan, tyrosine, and phenylalanine, all required for protein synthesis or for biosynthetic pathways leading to growth; failure of exogenous addition of these amino acids to completely overcome glyphosate toxicity in higher plants suggests that factors other than protein synthesis inhibition may be involved.

Basis of Selectivity:

Non-selective in agricultural crops; conifers are tolerant at some stages.

Symptoms:

Growth is inhibited soon after application followed by general foliar chlorosis (yellowish orange) and necrosis (browning), within 4-7 days in highly susceptible grasses and within 10-20 days in less susceptible species; chlorosis may first appear and be most evident on immature leaves and growing points; foliage sometimes turns reddish-purple in some species; re-growth of treated perennial and woody species often appears deformed with whitish markings or striations; multiple shoots (sometimes called 'a witch's broom' may develop at nodes.

Residuality:

None (<1month); crops can be planted or seeded directly into treated areas following application due to strong adsorption to soil.

Toxicity:

Oral LD50 = 5600 mg/kg - practically non-toxic (ROUND UP = >5000 mg/kg - practically non-toxic).

Additional comments:

Other herbicides are required to control weeds emerging after the application; rainfall within 6 hrs after application or heavy frost within 24 hrs may reduce control; ROUNDUP TRANSORB is rainfast as soon as 1 hr after application; for effective control of most perennial weeds, apply POST between bud and bloom stage; quackgrass can be treated in spring or fall when actively growing with at least 3-4 new leaves on emerged shoots.