One cold night in May is causing serious stress in September for some eastern Ontario apple farmers worried about the impact on their crops.

Dean Beckstead looks after about 30,000 trees at Smyth's Apple Orchard south of Ottawa and says a few hours of temperatures as low as -7 C one night in May could cost him as much as 20 per cent of his usual crop.

"We went out the next day and there was small fruit the size of your little finger just starting to form on the trees and they were [frozen] straight through, just completely black," he said.

Beckstead said he's finding most apples near the top of his trees, which takes more time and money to pick.

"No matter whether you have one apple on the tree or you have a thousand apples on a tree it costs you the same… to look after your trees and everything,"

 "You always expect or you always hope to have a nice average size crop to be able to pay the bills and maybe make some money yourself at the end of the season."

He said he has some crop insurance but he'll have to wait until the end of the season to see if he made any money this year.

The Ontario Apple Growers Association represents hundreds of orchards across the province and said many of them will probably be disappointed with this year's crop.

"There's a lot of expenses that are already there and (if) you have no apples, you have no income to pay for it," said chair Charles Stevens.

"It really is kind of hard but that is the industry."