Fruit growers 'complacent'

HAVELOCK NORTH - Complacency by orchardists in New Zealand's main pipfruit region, Hawkes Bay, contributed to last season's worst outbreak for several years of the bacterial disease fireblight, says an agricultural consultant.

John Wilton says the mix of complacency and warm weather created problems.

The disease is a political hot potato, because it is the main non-tariff trade barrier used by Australian orchardists to keep cheaper and better quality New Zealand apples out of their market.

The transtasman opposition has so far been supported by the Australian Government, in spite of New Zealand scientists showing that there is almost no risk of mature apples carrying the bacteria that spread the disease.

Australia is undertaking a risk analysis on importing New Zealand fruit, although some industry observers have suggested it might follow the Japanese in setting standards so tough as to make a high-volume trade impractical.

Whatever approach is used by the Australian Government, its apple growers are expected to play on the high-profile outbreak in the Hawkes Bay in their fight against New Zealand access to Australian pipfruit markets.

Mr Wilton told orchardists at a fireblight seminar and fielday at Havelock North that in a normal spring, the blossom was largely finished before climatic conditions were right for fireblight.

But last season, conditions were right early in the season, which meant high levels of bacteria were around to infect other blossom for the rest of the season.

The warm winter, without too many frosts, and then no significant frosts in spring were also significant. Frost was as good as a chemical spray for killing the bacteria.

"In the period around September 28, when braeburn were coming into full bloom, there were two or three days of showery weather and high temperatures," Mr Wilton said.

"The fireblight got into blocks that had flower and produced inoculant, which was around for the rest of the flowering. It hit orchards later as they came into the right stage of development.

"If you don't have frosts in the late flower stage you don't knock it back."

Fireblight bacteria can enter pipfruit trees through any opening, but usually the flower.

Once established, no chemical treatments can stop it and the only option is cutting off the infected part of the tree.

When the disease affects apple blossoms, the flowers die, leading to a fall in fruit yield. Later in the season, it also attacks branches and leaves.

To counter fireblight, New Zealand orchardists cut off the infected parts of trees or spray to remove the threat of bacteria to blossoms.

Mr Wilton said a copper spray was needed in the late dormant period and possibly a spray of the antibiotic streptomycin, though some strains of fireblight had acquired resistance to this.

"You need to take preventive measures. It is too late once the thing has hit."- NZPA