Table 2.2-4. Characteristics of preemergence herbicides.

Table 2.2-4. Characteristics of preemergence herbicides.
Herbicide1 Family Mode
of
action		 Site
of
action		 Injury
symptoms
atrazine Triazine Photosynthesis inhibitor D-1 quinone protein Interveinal yellowing and necrosis of older leaves
Axiom (flufenacet + metribuzin) Oxyacetamide + triazine Seedling growth inhibitor + photosynthesis inhibitor Multiple + D-1 quinone protein Looping of grass leaves at emergence; interveinal yellowing and necrosis of older leaves
Balance (isoxaflutole) Isoxazole Pigment inhibitor HPPD enzyme Chlorotic whitened plant tissue
Callisto (mesotrione) Callistemone Pigment inhibitor HPPD enzyme Chlorotic whitened plant tissue
Define (flufenacet) Oxyacetamide Seedling growth inhibitor Multiple Looping of grass leaves at emergence
Dual (metolachlor) Chloroacetamide Seedling growth inhibitor (shoot) Multiple Looping of grass leaves at emergence
Eradicane (EPTC) Thiocarbamate Seedling growth inhibitor (shoot) Multiple Looping and knotting of grass leaves at emergence
Harness/Degree or Surpass/Topnotch (acetochlor) Chloroacetamide Seedling growth inhibitor (shoot) Multiple Looping of grass leaves at emergence
Lorax (linuron) Urea Photosynthesis inhibitor D-1 quinone protein Interveinal yellowing and necrosis of older leaves
Micro-Tech (alachlor) Chloroacetamide Seedling growth inhibitor (shoot) Multiple Looping of grass leaves at emergence
Outlook (dimethenamid) Chloroacetamide Seedling growth inhibitor (shoot) Multiple Looping of grass leaves at emergence
Princep (simazine) Triazine Photosynthesis inhibitor D-1 quinone protein Interveinal yellowing and necrosis of older leaves
Prowl (pendimethalin) Dinitroaniline Seedling growth inhibitor (shoot) Protein Tubulin protein Stunted shoot growth; P deficiency symptoms; swollen roots
Python (flumetsulam) Sulfonamide Amino acid biosynthesis inhibitor (protein) ALS synthase Prevents true leaf emergence, stunted growth, chlorosis, or purpling
  1. See Table 2-1 for additional products containing these active ingredients.
  2. Residual: 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, soil type, and environmental conditions.
Table 2.2-4. Characteristics of preemergence herbicides. (cont.)
Herbicide1 Weeds
controlled		 Residual2 Common causes
of
failure/injury
atrazine Annual broadleaves and certain grasses L Triazine-resistant weeds; pH below 6.0; tolerant species such as fall panicum; lack of rain to activate
Axiom (flufenacet + metribuzin) 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
Balance (isoxaflutole) Annual broadleaves, some grasses M Lack of rain to activate; poor seed burial and soil types; cool/wet conditions increase chances of crop injury
Callisto (mesotrione) Annual broadleaves M Lack of rain to activate; interactions with certain OP insecticides will cause crop injury
Define (flufenacet) Annual grasses M Lack of rain to activate; crop injury due to adverse weather conditions
Dual (metolachlor) Annual grasses and certain broadleaves M Lack of rain to activate; emerged weeds at time of application; tolerant species
Eradicane (EPTC) Annual grasses, shattercane, seedling johnsongrass, nutsedge M Poor or delayed incorporation; cool, wet soils; Johnsongrass rhizomes not broken up by tillage
Harness/Degree or Surpass/Topnotch (acetochlor) Annual grasses and certain broadleaves M Lack of rain to activate surface applications; emerged weeds at time of application; tolerant species
Lorax (linuron) Annual broadleaves and certain grasses M Lack of rain to activate, too much rainfall causes leaching; tolerant species
Micro-Tech (alachlor) Annual grasses and certain broadleaves M Lack of rain to activate surface applications; emerged weeds at time of application; tolerant species
Outlook (dimethenamid) Annual grasses and certain broadleaves M Lack of rain to activate; emerged weeds at time of application; tolerant species
Princep (simazine) Annual grasses and certain broadleaves L Lack of rain to activate; triazine-resistant weeds; pH below 6.0
Prowl (pendimethalin) Annual grasses and certain broadleaves M-L Poor seed burial resulting in crop injury; lack of rain to activate
Python (flumetsulam) Annual broadleaves M-L Lack of rain to activate; ph <5.9 with high organic matter, in-furrow insecticide appliacation, high soil pH (>7.8), and/or sandy-gravelly soils leading to crop injury, tolearant species
  1. See Table 2-1 for additional products containing these active ingredients.
  2. Residual: 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, soil type, and environmental conditions.