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Ministry of Agriculture, Food and Rural Affairs


Trade Names: Dual Magnum, Dual II Magnum

Registration status: This herbicide is registered for use in tender fruit orchards as a soil residual herbicide under the trees.

When to suspect injury: Excessive rates on newly planted trees can cause injury. Do not use on soils with less than 2% organic matter.  If you notice symptoms of interveinal chlorosis, yellow to white margins and brown tips on older leaves, ask for a herbicide history of the field and determine the soil pH and organic matter.

Herbicide Information:  Knowing how the herbicide works will help to determine the likelihood of injury from either direct application or drift.  Consider how the herbicide works in plants, behaves in soils and what symptoms are common in other plants. 

Chemical Family: Acetanilide

Site of Action/WSSA Group:  Conjugation of acetyl co-enyme A/ Group 15

General Symptoms in Plants

  • Seedlings fail to emerge from soils treated with pre-emergent applications General stunting of plants due to root inhibition in cold soils
  • Seedlings are deformed following post-emergent applications
  • Leaves may be trapped or emerge underground

Symptoms in Tree Fruit

  • Slow growth and stunting from root injury, especially on newly planted trees
  • Rarely seen, only in cold, wet soil

Uptake and Translocation

  • Tree absorption generally through roots
  • Absorbed by germinating grasses mainly through shoot just above seed
  • Absorbed by germinating broadleaf weeds through roots and shoots
  • Translocated to growing pointsthrough phloem


  • Soil activity will be short, only 6 - 14 weeks

If you suspect herbicide injury, laboratory analyses of herbicide levels in plant tissue are necessary to confirm the presence of herbicides, although symptoms may be helpful in diagnosing which herbicides caused the problem

Both damaged and healthy plant tissues should be analyzed, because comparison levels are not readily available for many herbicides. Contact your lab for instructions on which plant parts should be sampled, how to handle and ship the sample, and what costs are involved to ensure an accurate and timely diagnosis.

S-Metolachlor injury to peach
Click to enlarge.