A South Africa farmer inspects his crop in file photo.
A South Africa farmer inspects his crop in file photo.

A quarter of South Africa's corn crop could be ruined, as extreme heat and dry conditions sweep through its corn-producing regions, industry experts said on Thursday.

Africa's biggest grain producer planted 2.656 million hectares for the 2015 season, according to January estimates, and shortages may result in reduced exports to some of its southern African neighbours.

The price of white maize, which is a staple among 90 percent of South Africa's population, has spiked to 2,636 rand ($224) a tonne, its highest level in a year.

"Prices have sky-rocketed, they have gone up by 33 percent in two weeks," said Piet Faure, a soft commodities analyst at CJS Securities.

Soaring temperatures in the North West and Free State provinces have caused maize and other grains such as sunflower and soya beans to deteriorate, head of the producer group GrainSA said.

"We have seen large areas where the damage is already irreversible," said Jannie de Villiers, GrainSA Chief Executive of reported.

The rolling power cuts that have gripped Africa's most advanced economy are also affecting the crops as irrigation systems stop when the power is turned off.

Eskom, which supplies about 95 percent of South Africa's electricity is battling to meet its daily demand of about 30,000 megawatts and has had to reduce demand through controlled power cuts.