METRIBUZIN (LEXONE and SENCOR)
LINURON (LOROX)

Mode of action: Photosynthesis inhibition

Specific mode: C1 class (metribuzin), C2 class (linuron)

Chemical family: triazinone (metribuzin), phenylurea (linuron)

Uptake: root and foliar

Movement: move from roots to vine, no movement from leaves

Common application: pre-emergence

Weed Control: annual grasses, annual broadleaves, perennials
[for Nebraska, grasses as foxtails, crabgrass and fall panicum, and broadleaves as kochia, lambsquarter, pigweed, common ragweed and wild mustard, and thistles]

Weed Stage: pre-emerged and early post-emerged broadleaves

Injury by Metribuzin

Potato Injury: Photosynthesis inhibitors result in the production of free radicals which disrupt cell membranes. Because of compounds upwardly movement in plant's xylem, symptoms appear in the leaves. These compounds do not prevent emergence but become effective when the plants are exposed to sunlight, form leaves and begin photosynthesis. Initial symptoms are a yellowing (chlorosis) of leaf margins and tips especially of older leaves. Yellowing first occurs between the veins and moves inward to the mid-vein. As injury progresses, leaves turn brown (necrotic) and die. Younger leaves are more affected as they enlarge. Plant death is not common but loss of yield and quality is. Symptoms are more pronounced in soils with pHs above 7.2 (alkaline). Varieties vary considerably in their sensitivity to injury. As a general rule with many exceptions, white and red-skinned varieties are more sensitive than russet-skinned ones. Russet Norkotah is one of the least sensitive and metribuzin has been successfully used early post-emergence on this variety.

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