Freezing temperatures across much of France this week may have caused severe damage to newly planted sugar beet, adding to the difficulties of a sector hit by crop disease and low prices in recent seasons.
Rapeseed could also suffer losses as the oilseed enters the important flowering stage, although cereals in the European Union's biggest crop producer were seen as less vulnerable, analysts said.
Parts of France have registered record sub-zero lows for April since Tuesday, prompting producers to try to protect vineyards and orchards with anti-frost systems.
Field crops are usually sturdier than fruit. But the arrival of intense cold just as sugar beet was emerging from the soil may have destroyed part of the crop, growers group CGB said.
In its initial assessment, CGB estimated that between 10,000 and 40,000 hectares of recently sown sugar beet had suffered massive losses that would require replanting, Timothe Masson, a CGB analyst, told Reuters on Wednesday.
That would represent as much as 10% of this year's sugar beet area that the CGB has estimated at around 400,000 hectares, already about 6% less than in 2020.
Tereos, France's biggest sugar maker, said on Twitter it was assessing damage with its cooperative growers and was in contact with seed suppliers after an 'unprecedented phenomenon'.
Affected farmers could plant sugar beet again, but that would depend on cost and seed availability, CGB's Masson said.
Legislation that reauthorised neonicotinoid pesticides, previously banned to protect bees, for sugar beet from this year to curb crop disease may also influence decisions.
France's farm ministry did not immediately respond to a request for comment on how the law would apply to replanting.
Rapeseed could see localised damage to flowering crops after a difficult growing season, consultancy Strategie Grains said.
The impact on cereals like wheat should be limited to some well-advanced crops, with plants often able to replace lost stems during subsequent growth, Stephane Jezequel, scientific director at crop institute Arvalis, told reporters.