Crop damage caused by frost looks a lot like copper deficiency. Leaf damage extends back from the tip of the leaf. Damage to seed heads can be easily confused too. Other than similar symptoms, there’s little evidence yet to link frost and copper deficiency.
The location of damage can help with diagnosis. Frost damage is often worse in lower parts of paddocks. Higher areas may have less damage. Moderate frost damage shows as yellowing at the level of the frost. Copper deficiency can occur anywhere in a crop depending on soil copper levels.
Copper deficiency occurs most on:
- coastal sandy soils
- sandy soils low in organic matter
- sandy duplex soils
- loams derived from granites
- peat soils.
Recent research in Western Australia didn’t find a link between frost damage and copper. Ross Brennan and Richard Bell’s trials aimed to see if micronutrients, including copper, could increase crop tolerance to frost. But the trials saw years with no frost events.
Can foliar copper protect against frost?
There’s no evidence of foliar copper reducing frost damage in broadacre crops. Copper can affect ‘ice-nucleating bacteria’. These bacteria have proteins that ice crystals form around. Copper can change these to become non-nucleating. Foliar sprays of copper have been tried, but the benefits don’t last long. For example, in citrus, a copper foliar spray had to be applied less than 10 hours before a frost event to limit damage.
This post is a revision of our 2014 article: Frost and Copper deficiency – similar symptoms different causes