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Ministry of Agriculture, Food and Rural Affairs

Metribuzin

Trade Name: Sencor, Lexone, Conquest

Registration status: This herbicide is registered for use on new and established trees in tender fruit orchards.

When to suspect injury: Injury may occur from drift up into trees from under-tree applications, or from neighbouring fields under windy conditions. Use caution on low organic matter soils, and if unusually heavy rains follow application.  If you notice symptoms of leaf yellowing, wilting or necrosis, look carefully at neighbouring fields, and at weeds in the treated area.

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: S-triazine

Site of Action/WSSA Group: Inhibition of photosynthesis at photosystem II - Group 5

General Symptoms in Plants

  • Susceptible weed and crop seedlings emerge through treated soil, but 2- 5 days later they show chlorosis and necrosis
  • At this stage, the seedlings are often so small they may not be noticed
  • Plants treated after they emerge show chlorosis and necrosis between leaf veins, followed by wilting

Symptoms in Fruit Trees

  • Leaves will show interveinal chlorosis and eventually chlorosis from either drift or root uptake
  • Symptoms may appear if heavy rains follow application, especially on low organic matter soil

Uptake and Translocation

  • Some uptake through the foliage, but the major route is via the roots
  • Translocation upward through the xylem.

Persistence

  • Not very persistant in soils: at normal use rates, the half-life is 1-2 months.
  • Poorly bound to most soils and soluble in water, giving it a potential for leaching
  • Persistence varies with the climate

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.

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