Diagnosing frost in narrow-leafed lupins

Narrow-leafed lupins tolerate frost in early growth stages but are susceptible when growing rapidly from flowering to early pod fill.

Plants affected at flowering develop wilted upper foliage
Severe frost kills the growing point in addition to flowers and young leaves
Pale pod surface spots and brown mushy lesions and dead discoloured seed
Cracked, discoloured stems with pithy centres
Frost affected lupin pods
Brown fungal stem infection after frost

What to look for

    Paddock

  • Low lying areas, light-coloured soil types, dry soil, and areas with more retained stubble are likely to be more damaged.

    Plant

  • Plants with wilted upper foliage that shrivels and dies, or blistered pods.
  • These frozen upper stems become discoloured (dark green directly after thawing) and associated foliage shrivels and dies.
  • Often the damaged tissue (stem and pods) will take on a brown colour due to bacterial fungal infection.
  • Stems have surface splits that turn brown with a mushy interior.
  • Pods have pale surface spots or blisters and brown mushy lesions.
  • Developing pods abort and fall off.
  • Developing seed may abort.
  • Unaffected parts of the plant grow, flower and set seed if there is sufficient time and soil moisture.

What else could it be

Condition Similarities Differences
Diagnosing anthracnose in narrow-leafed lupins Similar shepherd’s crook symptoms on stems Brown lesions and pink spores in the bend of the crook
Diagnosing group I herbicide damage in narrow-leafed lupins Bent and twisted plants Plants pale and slowly die without marked leaf necrosis
Diagnosing bean yellow mosaic virus - non necrotic in narrow-leafed lupins Bent necrotic upper stems Plants die back from growing point. Usually occurs in patches or edge of paddock

Where does it occur?

Temperature
Temperature
  • Frost damage occurs when night air temperature falls below -2°C.
  • Lupins become more susceptible throughout flowering and bud formation when the plant is rapidly growing.

Management strategies

  • Frost damage is irreversible however managing a crop to only avoid frost will come at a yield cost and potentially increased disease risk. It is advisable that after a frost event, to make note of the location and severity, as this will help to inform future crop choice and post frost decisions.
  • A comprehensive frost management strategy needs to be part of annual farm planning. It should include pre-season, in-season and post frost event management tactics.

How can it be monitored?

  • Check low lying, light coloured soil types and known frost prone areas first. Then check other areas.
  • To identify frost damage check for gaps in pod set on the flowering spike and open pods that have a scarred surface to check for mushy, shrivelled or abnormal grain.

Where to go for expert help

Mark Seymour
+61 (0)8 9083 1143
Page last updated: Thursday, 6 July 2017 - 1:01pm