Italian Scientists: Kiwifruit PSA Management Strategy Flawed

December 12, 2011

Italian Scientists Prove Kiwifruit PSA Management Strategy is Flawed

Italian scientists have recently published genetic research that shows that the kiwifruit industry’s PSA management strategy is on the wrong track.

Their breakthrough is timely as experience to date confirms that the current strategy to contain the disease is not working. It is spreading.

The Italian scientists proved that the current virulent form of PSA has evolved independent of other forms of the disease. Their research supports the claim that plant material with no symptoms of the disease can, in fact, be carrying the bacteria and introduces it into orchards.

The new virulent form has been spread throughout individual orchards through orchard management practices. The special type of virulent genetic material can be passed on to other PSA already existing in the vine.

The four Italian researchers, funded by the Italian Ministry of Agriculture and Forestry through the Agricultural Research Council, have also confirmed that the virulent form of PSA carries a gene that is resistant to copper and streptomycin. Again orchard experience shows that spraying these antibiotics on vines has not produced positive results. As well, orchardists have reported phytotoxic or plant poisoning problems from antibiotic sprays but their reports have been ignored or blamed on poor spray application technique.

Another important result from the Italian scientists’ investigation has been to show the ability of the current virulent form to breakdown essential oils that the plant produces, stores and uses as a natural chemical defence. This means the practice of removing vine foliage is a bad strategy as it removes the “factory” that produces these essential, protective oils.

Pukekohe based scientist Nathan Balasingham said the Italian findings are very timely for New Zealand kiwifruit orchardists.

“We can now fight the organism in the right jungle - cornered within the vine,” he said.

“Because PSA lives and proliferates within the plant we can manage the disease effectively,” Mr Balasingham says.

“A range of tools are already available and scientific evidence exists to abandon some of the current risky orchard management practices. The New Zealand-manufactured and proven technologies Thermomax and Agrizest together with Humic acid complexes give us a head start to manage this disease.

“Field evidence has already accumulated to show orchardists who have been using these materials, have reduced the level of fertilizer applications, stopped girdling and unnecessary foliar fertilizer applications. These orchardists are beginning to see more resilient and healthier vines in their orchards.”

Mr Balasingham said the integrated pest management process gives the industry the opportunity to manage the disease and still produce quality fruit that delivers higher returns. At the same time residue risks are abated and fertilizer and girdling cost are saved.

“There is a seamless migration to the right scientific strategy that will result in more effective management of PSA, maintain New Zealand’s hard earned market share and result in higher profits,” he said.

ENDS

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