New pest wrecking potato crop

WARWICK SMITH/Manawatu Standard

BACTERIA THREAT: Horticulture New Zealand's Potato Group chairman Terry Olsen.

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"We really don't know much about it. It is a very new pest here."Terry Olsen - Horticulture New Zealand's Potato Group chairman on the potato psyllid

The jury is still out on the impact the pest, the potato psyllid, will have on crop yields.

The insect spreads a damaging bacterium, liberibacter.

Horticulture New Zealand's Potato Group chairman Terry Olsen said information from potato growers suggested the psyllid has had between a 10 and 20 per cent impact on lowering potato yields, but not a lot is known about the insect's influence yet.

"Growers are all talking about it, and there is some uncertainty and concern about next year's crop."

The insect lives on solanaceous plants, which included tomatoes, capsicums and potatoes. Its botanic name is Bactericera cockerelli.

Solanaceous weeds and volunteer potato plants are likely to be reservoirs for the disease between potato crop cycles.

"We really don't know much about it. It is a very new pest here. In 2008, we saw it first and has become widespread since then," Mr Olsen said.

He has been harvesting potatoes at his Opiki property for the past three weeks.

"It's early still, but it looks as though it may have had a 10 to 12 per cent impact in reducing yield here.'

Mr Olsen said after talking to other growers, it looked as though crops harvested early in the season largely escaped damage, while those brought in since late April have shown psyllid impact.

"There is a lot of research going on, but as yet, we don't have a good fix on the pysllid in New Zealand. There is early evidence that it may thrive in warmer climates and those that have mild winters," he said.

"I think the answer will be a management package, rather than the use of agri-chemicals alone.

"There are also some indications that some varieties are more resilient to the pysllid than others," he said.

Mr Olsen believed while research study was likely to help in the longer term, most early information would come from grower observation.

"The impact of the pysllid is still an unknown and so is the insect. At this stage we just don't know the enemy well enough," Mr Olsen said.