Small Grains Underseeded with Peas, Vetch, 
and Small-seeded Legumes
Bob Parker
Reviewed October 16, 2008
•  diuron (Karmex or Direx)
winter oats and peas only
Rate  1.2 to 1.6 lb ai/A (1.5 to 2 lb/A of the 80% DF)
Time  After planting but before crop emerges.
Remarks  To control annual grasses, particularly Italian ryegrass, and broadleaf weeds in drill-planted winter oat–vetch or winter oat–pea mixtures in western Oregon and Washington.
Caution  Use lower rate on coarse soils. Do not use on sand, sandy loam, gravelly soils, exposed subsoils, or soils with less than 1% organic matter. Do not replant treated area within 1 yr after treatment. Do not apply after vetch or peas emerge.
Site of action  Group 7: photosystem II inhibitor
Chemical family  Substituted urea
•  triallate (Far-Go) +
•  diuron (Clean Crop Diuron 80WDG)
wheat or barley with Austrian peas, west of Cascades in Oregon only
Rate  1 to 1.25 lb ai/A triallate (1 to 1.25 quarts/A Far-Go) + 1.2 to 1.6 lb ai/A diuron (1.5 to 2 lb/A of the 80% DF).
Time  Apply triallate from up to 3 wk before planting until immediately after planting (should be incorporated by harrowing twice at right-angles). Apply diuron after planting but before crop emerges.
Remarks  For use on wheat–Austrian pea or barley–Austrian field pea mixtures only. This combination is more effective than diuron alone for control of ripgut brome, wild oat, and heavy infestations of Italian ryegrass.
Caution  Plant peas 2 to 3 inches deep. Do not disturb seeds when incorporating. Do not apply diuron on sand, sandy loam, gravelly soils, exposed subsoils, or soils with less than 1% organic matter. Do not use on oats.
Site of action  (triallate) Group 8: lipid synthesis inhibitor, but not an ACCase inhibitor; (diuron) Group 7: photosystem II inhibitor
Chemical family  (triallate) thiocarbamate; (diuron) substituted urea
•  MCPA amine or sodium salt
Rate  0.125 to 0.25 lb ae/A
Time  Spray when cereals are well tillered but before boot stage, and when small-seeded legume seedlings are 2 to 3 inches tall and peas are 4 to 6 inches tall.
Remarks  MCPA product labels differ; consult label for legumes that can be treated. Controls annual broadleaf weeds in cereals underseeded with alfalfa, trefoil, and red, alsike, white, or ladino clover. Use low gallonage and low spray pressure to avoid excessive injury to legumes. Spray when cereals are well tillered but before boot stage. Cereals or weeds must provide a protective canopy for legumes.
Caution  Not for cereals underseeded with vetch or sweet clover.
Site of action  Group 4: synthetic auxin
Chemical family  Phenoxy acetic acid