Glyphosate

Physiological basis of tolerance

1. Classic target enzyme modification 2. Resistant biotype. Palmer amaranth may have up to 75 copies of EPSP gene.

The lack of soil activity from glyphosate is attributed to what two factors?

1. Rapidly absorbed by the soil. 2. Rapidly degraded.

What are the limitations of a selective placement applicator?

1. Slow. Since glyphosate in simply wiped onto the foliage, excessive speed reduces the amount of control. 2. Often two applications are needed, that are either a sequential or two passes, diagonal to each other, in the same application. 3. Application must be delayed until a sufficient difference develops. By this time, a substantial portion of the competition has already occurred. Benefit is not realized until subsequent crops.

When was glyphosate introduced?

1971

After 24 hours, what percent of glyphosate was absorbed?

45%

LD50 of Glyphosate

5,400 mg/kg

What enzyme does glyphosate disrupt?

5-enolpyruvateshikimate 3 phosphate (EPSP)

After 48 hours, what percent of glyphosate was absorbed?

53%

What is frequently added to glyphosate tank mix?

AMS.

Translocation of Glyphosate

Apoplastic and Symplastic

What does EPSP do?

Catalyzes reversible transfer of the enolpyruvyl group from phosenolpyruvate (PEP) to shikimate 3-phosphate.

Soil activity of glyphosate

Due to tight absorption and rapid degradation, no soil activity

Why is AMS added to glyphosate tank mix?

If the water is hard with alot of NA a and Ca ions, these cations attach themselves to the glyphosate and reduces efficacy. When AMS is added, the ammonium cation attaches to the glyphosate and it is still biologically active.

What formulation does Roundup have?

Isopropylamine salt

What weed can interfere with glyphosate?

Lambsquarter. They have glands that excrete calcium crystals onto the leaf surface.

When is addition of a surfactant justified?

Low volume and very dense vegetation

Rodeo Formulation

None

Which herbicide does glyphosate compare to?

Paraquat

Glyphosate interferes with what amino acids?

Phenylalanine Tyrosine Tryptophane

Glyphosate's tight absorption to the soil is due to what?

Phosphate group, which gives the molecule a very strong dipolar, positive charge. It acts like a cation in the soil.

Glyphosate's rapid degradation is due to what?

Phosphate group. Being a simple molecule and desirable to microbes due to the phosphorus molecule, microbes readily degrade it.

Absorption of Glyphosate

Rapid. A 24h = 45% absorbed 48h = 53% absorbed

Which glyphosate is targeted towards aquatic market?

Rodeo.

isopropylamine formulation of glyphosate?

Roundup

When did the patent expire on glyphosate?

Sept 2000

What pathway does glyphosate disrupt?

Shikimic acid pathway

What was the first selective placement applicator?

Stoneville wiper. The objective is to deposit glyphosate on the foliage of the weeds that extend above the crop.

What formulation does Touchdown have?

Sulfur Sulphosate

Sulphosate formulation of Touchdown

Touchdown

Where is glyphosate used?

Wherever complete vegetation control is needed.

What structure does glyphosate have?

aliphatic (no ring)