Table 2.4-4.

Table 2.4-4. Characteristics of preplant or preemergence soybean herbicides.
Herbicide¹ Family Mode of Action Site of Action Injury Symptoms Weeds Controlled Residual² Potential Problems
  1. See Table 2.4-1 for additional formulations or trade names containing these same active ingredients.
  2. N = no soil activity; S = one or two weeks soil activity; M = one or two months; L = full season, may carry over under certain conditions or if misapplied. Residual activity is dependent upon rate.
Authority / Spartan (sulfentrazone) Aryl Triazolinone Cell membrane disrupter PPO Stunted growth, yellowing, seedling death Annual broadleaves M-L Lack of rain to activate; emerged weeds at application
Axiom (flufenacet + metribuzin) Oxyacetamide + triazine Seedling growth inhibitor + photosynthesis inhibitor Multiple + D-1 quinone protein Heart-shaped unifoliate leaves; looping of grass seedlings; interveinal yellowin Annual grasses and broadleaves M Lack of rain to activate; emerged weeds at time of application; triazine-resistant weeds; crop injury due to adverse environment
Canopy (chlorimuron + metribuzin) Sulfonylurea + triazine Amino acid biosynthesis inhibitor (protein) + photosynthesis inhibitor ALS synthase + D-1 quinone protein Interveinal yellowing and necrosis of older leaves; stunting Annual broadleaves L Lack of rain to activate, high pH soils leading to carryover
Command (clomazone) Isoxazolidinones Pigment inhibitor Cartenoid biosynthesis Chlorotic; whitened plant tissue Annual broadleaves and grasses L Insufficient application rate; uneven incorporation
Dual / Cinch (metolachlor) Chloroacetamide Seedling growth inhibitor (shoot) Multiple Heart-shaped unifoliate leaves; looping of grass seedlings Annual grasses and certain broadleaves M Lack of rain to activate; emerged weeds at application; tolerant species
Lorox (linuron) Urea Photosynthesis inhibitor D-1 quinone protein Interveinal yellowing and necrosis of older leaves Annual broadleaves M Lack of rain to activate; tolerant weeds
Micro-Tech (alachlor) Chloroacetamide Seedling growth inhibitor (shoot) Multiple Heart-shaped unifoliate leaves; looping of grass seedlings Annual grasses and certain broadleaves M Lack of rain to activate; emerged weeds at application; tolerant species
Outlook (dimethenamide) Chloroacetamide Seedling growth inhibitor (shoot) Multiple Looping of grass leaves at emergence Annual grasses and certain broadleaves M Lack of rain to activate surface applications; emerged weeds at time of application, tolerant species
Prowl (pendimethalin) Dinitroaniline Seedling growth inhibitor (root) Tubulin protein Swollen roots; stunted growth; swollen, brittle stem with surface application of Annual grasses and certain broadleaves M-L Poor incorporation; lack of rain with surface-applied Prowl; tolerant species
Pursuit (imazethapyr) Imidazolinone Amino acid biosynthesis inhibitor (protein) ALS synthase Stunted growth; purple foliage; inhibited root growth Annual broadleaves, some grasses L Weeds too large or hardened-off; tolerant weeds
Python (flumetsulam) or FirstRate (cloransulam) Sulfonamide Amino acid biosynthesis inhibitor (protein) ALS synthase Prevents true leaf emergence; stunted growth, chlorosis, or purpling Annual broadleaves M-L Lack of rainfall to activate; in-furrow insecticide application, high soil pH, and/or sandy-gravelly soils leading to crop injury
Scepter (imazaquin) Imidazolinone Amino acid biosynthesis inhibitor (protein) ALS synthase Stunted growth; purple foliage; inhibited root growth Annual broadleaves L Lack of rain to activate; tolerant weeds
Sencor (metribuzin) Triazine Photosynthesis inhibitor D-1 quinone Interveinal yellowing and necrosis of older leaves Annual broadleaves M Triazine-resistant weeds, crop injury due to adverse environment; lack of rain to activate
Treflan (trifluralin) Dinitroaniline Seeding growth inhibitor (root) Tubulin protein Swollen roots; stunted growth; swollen hypocotyl Annual grasses and certain broadleaves M-L Poor incorporation; tolerant species