UP to a third of Victoria's cereal crops have been hit by frost and fungal disease this season.
Reports are emerging of white "dead heads" appearing in maturing green Mallee cereal crops caused by crown rot, a fungal disease historically more of a problem in northern NSW.
And growers who have begun harvesting canola and barley crops in the northwest of the state are discovering losses from frosts earlier in the season.
The losses are a cruel blow to farmers hoping for reasonable crop yields while grain prices remain relatively high.
Curyo grower Jim Rickard said some farmers were facing losses of 20-30 per cent from crown rot.
"It's always disappointing to have losses," Mr Rickard said.
Agrivision Consultants agronomist Kent Wooding said growers harvesting canola crops in the Mallee found frost had cut yields, although the full extent would not be known until the harvest was in full swing.
"It looks like isolated pockets in the Mallee have been affected," Mr Wooding said.
"Some may be the result of stem frost of two months ago."
According to the Grains Research and Development Corporation, crown rot is hosted by cereals and grass weeds.
It survives in plant residues, which can infect new crops.
Department of Primary Industries plant pathologist Grant Hollaway said a shift towards stubble retention and tighter rotations in recent years had helped increase its prevalence in Victoria.
Dr Hollaway said the disease needed a wet start to a season, followed by a dry finish.
CIMMYT International senior pathologist Julie Nicol said crown rot was "definitely a big problem" this year in South Australia, NSW and Queensland as well as in Victoria.
Up to 50 per cent losses had been reported in northern NSW wheat crops, and Dr Nicol said: "This has been a perfect year for crown rot."