Chilly start good for stonefruit
From the August 2006 edition of Agriculture Today.
Stonefruit growers on the sub tropical NSW North Coast have experienced a bumper flowering and fruit set, thanks to a winter of abundant "chill hours".
Low chill stonefruit is aimed at the market in September, October and November ahead of the traditional stonefruit that appears in summer from districts such as Stanthorpe, Orange, the Sydney Basin and Northern Victoria.
But one of the risks is that the winter on the North Coast can be too warm - affecting flowering and fruit set.
"Not so this year," said NSW DPI horticulturist Phillip Wilk, based at Alstonville.
"We’ve had 50 per cent more chill hours than last year and that has set up a great start to the season."
Stonefruit varieties are defined according to their chill hours - that is, by the number of hours below 12.8 degrees C that they need to accumulate in winter to trigger flowering.
"Some low-chill varieties need as little as 100 to 200 chill hours a year while high-chill types may need up to 1200 hours," said Mr Wilk.
"If you don’t get the chill hours that a variety requires, you may have to thin the flowers and fruit very lightly and you can still lose pea-sized fruit or buds that just drop off and fail to set.
"That was the case last year when there was an inadequate chill and fruit yields were down 30 to 50 pc.
"But this year, some varieties were flowering in the first week of June and the buds are good, tight and strong, making thinning much less risky.
"Hopefully, the other ingredients will fall into line for a bumper crop this spring and early summer."
Mr Wilk said North Coast stonefruit growers were starting to use data loggers to get a detailed understanding of the temperature variation on individual orchard blocks during winter.
"We are finding huge differences in the number of chill hours between blocks, even on the one orchard," he said.
"This is important because growers need to match the chilling requirement of their varieties to the micro-climate of their site."
Mr Wilk said most growers are aiming to match the right variety for the appropriate block, so they get a sequential harvest, allowing them to effectively manage their harvest labour force.
"Growers are usually replanting about 20 pc of their orchard to new varieties in any one year, so the opportunity is always there to make changes based on more accurate information."
Contact: Phillip Wilk, Alstonville, (02) 6626 2400.
