New Zealand homes in on two PSA strains as kiwi harvest approaches
New Zealand’s kiwi industry is focusing on controlling and finding the source of two types of vine disease as the new harvest approaches, according to John Burke, general manager of the newly formed Kiwifruit Vine Health Inc.
So far, 126 orchards have tested positive for P. syringae pv. Actinidiae, Burke said, and the disease is concentrated in the Bay of Plenty on the North Island. The disease has affected less than 1% of kiwi-growing land by area, Burke told FreshFruitPortal.com.
“With the theory that it’s concentrated, we’ve been cutting and removing vines to stop the infection from spreading,” he said. “It’s business as usual for all other orchards.”
Burke, who also grows kiwis, said the season is going well so far. No importers of New Zealand kiwis have refused the fruit, which is not affected by the disease, he added.
Production “may be the same or higher than last year,” he said. Kiwi exporter Zespri reported 98.5 million trays sent from New Zealand in the 2009-10 season.
Through genetic testing, researchers have found two isolates, or strains, of PSA: one Italian-French and one Asian. The Italian-French strain is more virulent than the Asian one, and is responsible for widespread damage in Italy, Burke said.
PSA shows up as discolored buds, dark brown spots on leaves and cankers on twigs, according to the European and Mediterranean Plant Protection Organization. The disease was first described in Japan in 1980, and was first spotted in Europe in 1992. A big outbreak in Italy in 2007-08 caused up to 2 million euros in damage, according to EPPO.
Researchers may know more about the disease and its origins in two to three months, Burke said.
“We’re looking at this as a long-term project,” he said. “We’ll be keen to share with (the results) the rest of the world.”
Photo: European and Mediterranean Plant Protection Organization