Diagnosing groups D J herbicide damage in cereals

These are pre-emergent herbicides for the control of grasses and some broadleaf weeds in specific cereal crops. Damage symptoms are seen around plant emergence and plants can recover completely.

Dying wheat seedlings with short thick coleoptiles and spade-tip roots
Distorted trifluralin affected leaves (left).
Worst plants have thickened coleoptiles and stubby roots. Less affected plant can resemble have root lesion nematode damage
Shallower sown plant are more affected

Symptoms vary slightly according to group:
Group D — symptoms appear as the crop emerges. In most cases targeted weeds do not appear or are severely root pruned and do not survive.
Groups J — symptoms appear underground or as the weeds and crop emerge and are less severe than Group D.

 

Mode of Action Group

Chemical name

Example trade name
Group D

Dinitro-anilines

trifluralin

Treflan®

 

pendimethalin

Stomp®

Benzamides propyzamide Kerb®
Group J  Thiocarbamates

Thiocarbamates

triallate

Avadex®

  prosulfocarb

Boxer Gold®

 

What to look for

    Paddock

  • Poor or intermittent emergence and stunting that often varies between drill rows or soil types.

    Plant

  • Reduced or poor seedling emergence.
  • Shortening and thickening (Group D) of coleoptile.
  • Leaves emerged from shortened coleoptile unable to reach the soil surface.
  • Emerged shoots are often swollen and bright green (Group J), or have twisted and distorted leaves (Group D).
  • Severely affected plants have pruned, and thickened roots with stubby or spade tips.
  • Less affected plants can have brown poorly branched roots.

What else could it be

Condition Similarities Differences
Diagnosing group K herbicide damage in cereals Variable emergence, weak seedlings that may be worse in rows on sandy, low organic matter soils. Group K herbicide damaged plants do not have thickened coleoptiles or stubby thickened roots.
Diagnosing poor seed-soil contact in crops Variable emergence, weak seedlings that may be worse in rows. Poor seed-soil contact is more common in dense stubble and on heavy or very cloddy soil. Plants will not have thickened coleoptiles.
Diagnosing allelopathy in cereals Variable emergence and weak seedlings. Silly seedling plants remain spindly, have weak thin roots and lack thickened coleoptiles.
Diagnosing group C herbicide damage in cereals Seedling death that may be worse in rows and on sandy, low organic matter soils. Group C herbicide damaged plants will have root damage.

Where did it come from?

Contaminated soil
Contaminated soil
Low organic matter
Low organic matter
Wet conditions
Wet conditions
  • These herbicides can be lost to the atmosphere (particularly trifluralin) but are tightly bound to soil particles when incorporated into the soil. When these herbicides are used with no-till seeding, crop damage usually results from soil with herbicide being placed too close to the seed. Other contributing factors include:
  • Sowing too fast throwing herbicide treated soil into the adjacent furrows.
  • Variable depth of sowing.
  • Light-textured soils with low organic matter may be more affected.
  • Wet or waterlogged soil.

See also

Where to go for expert help

Page last updated: Friday, 29 May 2015 - 2:02pm