Manawatū growers say the jury is still out whether the release of a wasp will be successful in controlling the tomato potato psyllid. The pest has wreaked havoc on many commercial and home crops. A new biocontrol agent Tamarixia trioaze, a parasitoid wasp which destroys the psyllid, has been released in Hawke’s Bay and Canterbury. Ōpiki potato grower Terry Olsen said Horticulture New Zealand (HortNZ) had been working on a biocontrol agent for the psyllid when he was Potatoes New Zealand chairman many years ago.
Opiki Potato grower Terry Olsen wants to see how the newly released wasp deals with controlling the psyllid outdoors. “We’ll see how it goes out in the open. It might work well in glasshouses, but we’ll see how it operates in wider spaces.” Like all bio-control agents, he hoped this would work for outdoor growers, but did not think it would be 100 per cent effective. “HortNZ seems to think it will work, otherwise it would not have released tamarixia. They’ll analyse what they see and we’ll see how it goes.” He said the jury was out on how the wasp would go with the pest. “Hopefully it’ll work and that will encourage people to keep working on other beneficial biocontrols.” Olsen said the wasp would save some spraying costs as chemicals were expensive for growers to apply.
HortNZ said the initial releases were the start of a wider planned release and monitoring programme that was being supported with funding through the government’s Sustainable Farming Fund (SFF). The psyllid had caused enormous problems for potato, tomato, capsicum and tamarillo growers in New Zealand since it was discovered in 2006. Tamarixia is a tiny wasp that lays its eggs on the psyllid, which then hatch and eat the psyllid.
Co-ordinator for the Vegetable Research and Innovation Board, Sally Anderson said growers had been patient at waiting for a psyllid control. She said Tamarixia was found in the United States and Mexico as a naturally occurring parasitoid of the psyllid. The wasp was released onto African boxthorn – a psyllid over-wintering host, as there are no host crops such as potatoes or tomatoes in the ground. Anderson said her hope was that it would be available for release by commercial growers this summer.
“There are a couple of New Zealand companies which can breed them up, so we can establish a supply. The first live ones we released were from a commercial breeding place in Mexico, but we want to breed them in New Zealand and it is cheaper than importing them.” At the moment most growers use insecticides to get rid of pests. However, a pesticide would get rid of all insects, including the beneficial ones, such as ladybirds and lacewings, said Anderson. “Our research has to look at the sprays as they will kill Tamarixia too. We are dealing with a biological system and they are complicated.” She said the pest would cope anywhere where potatoes would grow. “So it will survive in the New Zealand climate.” Anderson said they were pinning their hopes on tamarixiaand there were no other biological controls in the pipeline.