Diagnosing group C herbicide damage in narrow-leafed lupins

This category contains root pre-emergent Group C herbicides such as simazine and metribuzin that are routinely used in lupins. Post-emergent atrazine damages lupins.

Necrotic leaf tips are rolled and fold in a claw shape

Oldest growth is affected first and worst

Plants look pale and stunted

Seedling death from post-emergent atrazine spray (unsprayed on right)

What to look for

Paddock

Pale and scorched seedlings with worse damage on sandy soils with low organic matter.

Plant

Seedlings emerge normally but tips of leaflets roll turn ivory coloured and shrivel. Necrosis progresses down the leaflet as the leaf develops a claw shape.
Necrosis moves to successively younger leaves, as the plant becomes pale and stunted, until it recovers or dies.

Where does it occur?

Spraying herbicide

Spraying herbicide

These herbicides are more active in moist soil.
Situations where the herbicide is close to seed. This includes shallow sowing or heavy rain washing herbicide into furrows in ridged seedbeds.
Topsoils with low adsorption capacity such as sands with low organic matter.

Management strategies

No treatment - the plant becomes pale and stunted, until it recovers or dies.

How can it be monitored?

It is important to observe withholding periods for these herbicides to avoid damage to following crops.
Take care when spraying not to spray non-tolerant varieties.

Further information

HerbiGuide [1]

GRDC Incrop herbicide use [2]

APVMA registered products database [3]

Links
[1] http://www.herbiguide.com.au/
[2] http://grdc.com.au/GRDC-FS-InCropHerbicideUse
[3] http://apvma.gov.au/

Important disclaimer

The Chief Executive Officer of the Department of Primary Industries and Regional Development and the State of Western Australia accept no liability whatsoever by reason of negligence or otherwise arising from the use or release of this information or any part of it.