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Ministry of Agriculture, Food and Rural Affairs


Trade Names: Princep Nine-T, Simadex, Simazine 480

Group 5

Site of Action: Inhibitors of photosynthesis at photosystem II, Site A


At first symptoms include:

  • Interveinal chlorosis of leaves
  • Yellowing of margins of leaves

Followed by:

  • General foliar chlorosis and necrosis
  • Browning of leaf tips
  • Older leaves show more injury than new

Uptake and Translocation

  • Absorbed by roots; little or no foliar absorption
  • Translocated upwards in xylem, accumulating in apical meristem and leaves


  • Moderate residual
  • Half life: 30 days in fields, 60 days in ponds
  • Simazine is more persistent in high pH soils
  • Residues can injure crops 1 year after application
Simazine injury - chlorosisClick to enlarge.