Unexpected frost on the North Coast killed many of the small developing stone fruit that was already set and wiped out many open flowers. It also damaged large numbers of structural limbs on the north facing side of many trees.

North Coast stone fruit growers rely on getting their stone fruit to market early to compensate them for the high cost of production, yet this year they will not only get their crops to market late - they also have less and small fruit.

The reason is the odd weather: unexpected frosts dipping to a record low of minus 6.5 degrees Celsius, combined with onethird of the average rainfall.

The low-chill stone fruit industry is established in the sub tropical climates around Alstonville, Stuart’s Point and Gosford in NSW, and southern Queensland.

It is primarily aimed at supplying the early peach and nectarine market where fruit is usually harvested between September and late November.

Generally, the varieties grown are those from the University of Florida which require very little chilling or low chill to flower and fruit successfully.

In sub tropical areas, the trees usually struggle to accumulate enough chilling to flower and set fruit, however, this season the whole region was slammed with some of the coldest night time temperatures in recent times.

Up until June, most stone fruit trees had not received enough chill and it seemed that flowering would be very patchy.

Normally the cumulative chill hours for the season range between 200 hours at Alstonville to 450 to 600 hours at Bangalow.

This winter there were quite a few days in June and July at Bangalow where night time temperatures were below zero.

On July 19, it was recorded at a record minus 6.5C.

This frost killed much of the small developing fruit that was already set and wiped out many open flowers.

It also damaged large numbers of structural limbs on the north facing side of many trees.

Most growers have a number of methods to reduce mild frost damage to their orchards.

These include using large fans to keep air circulating, using overhead sprinklers and using chemical sprays.

Unfortunately, this season nothing seemed to work. The prolonged cold spell was coupled with a drier than normal rainfall pattern.

The whole northern region missed out on its normal summer rainfall resulting in clear nights and warm days.

Rainfall was approximately one third of its normal average for the year.

The odd weather pattern has resulted in a late stone fruit crop that will be down by approximately 20 per cent volume.

Growers have been reluctant to thin fruit or flowers early as a precaution against a late frost.

This unfortunately may produce a larger than normal volume of smaller fruit.

The abnormal weather pattern may mean that the region will in future receive a shorter sharper burst of chill rather than the slow build-up that normally occurs as winter approaches.

If this is so, growers will need to adjust the varieties they grow to take account of the short colder conditions so that early flowering does not occur before sufficient chill has accumulated.

Contact Phillip Wilk, Alstonville, (02) 6626 2450