Imazethapyr is a broad-spectrum herbicide for use in soybeans and other leguminous crops. It provides excellent weed control when applied pre-plant, soil incorporated, pre-emergence and early post-emergence. Depending on the weed problem and local conditions, imazethapyr is applied at rates ranging from 40 g a.i./ha to 140 g a.i./ha.
Imazethapyr acts by inhibiting the enzyme acetohydroxy acid synthase (ALS). This enzyme is common to the biosynthetic pathway for the three amino acids isoleucine, leucine and valine. The inhibition causes a disruption in the protein synthesis and other subsequent biochemical reactions, which in turn inhibit plant growth.
Imazethapyr is readily absorbed by roots and leaves, translocated in both symplast (phloem) and apoplast (xylem), and accumulated in mersistematic tissue.
When treated with imazethapyr, the following symptoms are observable on the weeds: inhibition of growth, especially growing points, followed by purple discoloration and necrosis of the leaves within 2 to 4 weeks. After pre-emergence or pre-plant soil incorporated treatments, susceptible annual weeds may germinate and emerge; however, normal growth ceases at the cotyledon stage in broad-leaf weeds and before the two-leaf stage in grasses.
Rapid metabolic degradation is the basis of selectivity. Susceptible weeds either can not metabolise imazethapyr or metabolise it too slowly for detoxification.
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