Little pest threatens Northland tamarillo crops

The tomato/potato psyllid (TPP) sucking the life out of the $1.9 million fledgling tamarillo industry continues to threaten other susceptible crops while the industry searches for solutions.
With tamarillo harvesting about to get underway growers say production will again be drastically affected by TPP.
New Zealand tamarillo growers have already halved from the 120 registered five years ago and of those 60, only 45 remain active growers - 20 of these in Northland, the majority of the remainder in the Bay of Plenty.
The North American psyllid insect, which sneaked under New Zealand's biosecurity radar in 2006 has now carried its harmful bacteria nationwide threatening not only tamarillo crops, but tomatoes, potatoes, capsicums and cape gooseberries.
Interestingly the psyllid, which devastates tamarillo crops, actually has a preference for tomatoes and potatoes but because these plants are annuals and quicker to replace the effects are not as great.
Wind borne, the 2mm psyllid, which looks like a small cicada carries the bacterial pathogen "liberibacter" which causes rapid dieback of tamarillo trees - many dying within two weeks of being infected.
Tamarillo Growers' Association manager Robin Nitschke, who grows 6000 trees in a commercial operation at Maungatapere says he has lost around 30 per cent (2000) of his tree to the psyllid. He knows other orchardists who have experienced 70-80 per cent tree loss, "and that's even with a good management programme." The Sustainable Farming Fund has contributed $600,000, industry groups $330,000 and industry in-kind contributions totalling $550,000 has been committed to the fight against TPP and liberibacter. The three-year research project aims to better understand TPP behaviour, refine "soft" chemical sprays, and trial biological controls such as the tamaraxia wasp and the breeding of trees resistant to liberibacter. Growing trees under cover is also being investigated.
With the picking season about to commence even orchards with aggressive psyllid-control programmes are still reporting tree losses, so with volume down there is likely to be fewer tamarillos on the domestic market this year.
Growers last year experienced a 25 per cent drop in production with around 350 tonnes of tamarillo grown nationally - 35 tonne valued at around $350,000 exported, mostly to America.
The Australia market initially banned NZ tamarillo, but now allow imports which have been extensively fumigated.
"However this causes a loss in the quality and taste of the fruit," says Mr Nitschke.
Liberibacter is spread naturally from plant to plant by the sap-sucking insects that inject saliva into the plant by feeding on the underneath side of the leaf. Some trees can take three to six months to die while others can be dead with two weeks.
Fortunately, replacement plants can be returned to the same soil without residual risk.
"Most growers propagate their own trees so replacement costs are kept to a minimum. The two year wait for the trees to mature and fruit however causes lost production, loss of income and of course additional labour costs, " Mr Nitschke said. "It's also very depressing to see your orchard dying."
Acknowledging the risk Mr Nitschke felt there was still an opportunity for good future returns in tamarillo. "The resilient growers will hang in and we will end up a solid core of dedicated growers." He would like to see information regarding TPP passed on by nurseries nationwide as the home gardeners also need to recognise and control the insect on the homefront. Mr and Mrs Nitschke has been commercially growing for around three years and employ two additional workers over the main season usually April to October, when the fruit is handpicked and packed and three trees pruned at the end of the season.
A commercial kitchen operates on the property that makes and sells chutneys, relishes, jams, sauces and vinegars.