Extreme heat in South Australia is leading to heavy losses for stone fruit growers, with their produce burning from the inside out.

Dried Tree Fruits Australia chairman Kris Werner, who grows stone fruit at his property in Waikerie, between Adelaide and Mildura, said many growers were losing their fruit to 'stone burn' due to the heat.

"The stone burns them, which means they burn on the inside, they become squashy and you can't use them," Mr Werner said.

The extreme heat has cost Renmark stone fruit grower and packer Dino Cerrachi up to 30 per cent of some stone fruit varieties this season.

Stone fruit grower Dino Cerrachi says the extreme heat and direct sunlight cooks the fruit and makes it go "jammy". ( Supplied: Dino Cerrachi )

"It's extremely hot and we are expecting 46, possibly 47 degrees [Celsius]," he said.

"There will be quite a lot of damage from direct sunlight, especially on the north-western side of the trees, or any exposed areas at the wrong time of that sun position.

"Basically, it just sort of cooks that side or that part of the fruit that has the direct sunlight for a length of time and it gives you an impression that it is soft, but it has actually gone jammy from being cooked."

Race against time to get fruit of trees before extreme heat

Riverland stone fruit grower Dino Cerrachi says they expect to see crop losses of 25 to 30 per cent for some of their varieties due to the extreme heat. ( Supplied: Dino Cerrachi )

Mr Cerrachi said he is racing against the clock, trying to get as much fruit off the trees as possible, before the extreme heat hits throughout the day.

"We are harvesting peaches and nectarines, both white and yellow, and we only have from daybreak until about 10.30-11 o'clock to pick all of that fruit and five varieties," he said.

"We have got a lot of ground to cover in a very short time … it's already too late to be picking peaches at this point in time because the skin is very sensitive, and they will show up all sorts of markings."

Mr Cerrachi said he had tried to increase his workforce to get as much fruit off the trees as possible, but struggled to find experienced workers.

"We need experienced people and often when you look for more they haven't got the experience, but we need to get more people and try to get it off [the fruit] as quickly as possible," he said.

"However, the fruit that we actually put into the boxes is still of very high quality and that is one thing that we are extremely happy about, that the fruit that does make it through is of very good eating quality."

Growers have to use more water to keep trees cool

Mr Werner said they increased their water usage to keep the trees cool, which was a worry moving into next season.

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"Our concern is that there won't be a big allocation next season and we wanted to try and carry some water forward, so it just means we won't have water to carry forward, so we have to buy it," Mr Werner said.

"The biggest concern is that these temperatures are actually occurring because the last drought and water buyback means a third of the land around us isn't being watered anymore, so it's only going to make the temperatures get hotter."

Stone fruit growers try to get as much fruit off the trees in the early mornings before temperatures soar, causing more fruit damage. ( Supplied: Dino Cerrachi )

Mr Werner said they were finding that the quality of dried apricots was impacted as the increased watering of the trees washed the sugar out of the fruit.

"You can't get sugar into it because you have to have that six to eight day cycle where you have the drying and the wetting, and because it is so hot you are keeping them fairly wet constantly," he said.

"The sugar just doesn't get a chance to get into the fruit, so the flavour is not going to be there."

Mr Cerrachi said the high temperatures caused the trees to shut down and water was essential to prevent further fruit damage.

"What happens when it shuts down, it seems to slow down the ripening process," he said.

"It's just so hot that the trees go into saving itself mode.