Tomato Potato Psyllid Pest 2010

May 2010

Research at Lincoln University to control a psyllid that threatens solanaceous crops

The tomato/potato psyllid from North America was first found in New Zealand in 2006, and is still spreading throughout the country. The psyllid can transmit a bacterium, Liberibacter, that is believed to cause diseases that can drastically reduce the quality and yield of infected crops. Nobody knows how it got here but many in the growing industry suspect it sneaked through - most likely on flowers.

Psyllid is an insect pest, like a 2-3mm cicada, or aphid. It was first found in New Zealand in 2006 on tomatoes. It thrives in warm, dry conditions and harms plants by feeding on them, injecting toxins into the leaves, and spreading a disease called liberibacter. It affects potatoes, tomatoes, tamarillos and capsicums.

Up to 60 per cent of the New Zealand potato industry is for "processed" potatoes which become fries and crisps. Potatoes infected with psyllid cannot be fried and end up as waste, or stockfeed. Farmers dealing with psyllid in potatoes for the fresh market also have issues including lower production and higher costs.

Classic symptoms of psyllid damage are leaf edges curl, the growing tips turn purple and leaves turn yellow. As the starch in the potatoes is converted to sugar, vegetables appear scorched and plants collapse prematurely.

Potatoes are also affected by the Potato Tuber Moth seems to be some concern that any new regime introduced to deal with pysllid may compromise existing controls around tuber moth

Robin Oakley is a fifth generation grower. Oakley's Premium Fresh Vegetables is a locally owned business, employing a mixture of 35 staff although they often need more casual labour at busy harvest times.

They supply fresh produce to the Supermarkets. They grow 80ha of potatoes, 150ha brassica, 50 ha pumpkin, 13ha of parsnip and some arable crops.

Although the psyllid has been in NZ since 2006 Robin says theyve had little sign of it in South Island. He says he knew little about it until this season when it started showing up before Xmas. He says it is a new bug that the growers have to learn to live with.

Robin says that growers want good information on how to detect and treat the pest. Hes interested in Nadines work with the traps and wants to know what the protocols are around that. But the primary focus for now is around the effective use of sprays what should they best be using, when and how long. What is the timing between sprays and is there any possibility of resistance developing.

Nadine Berry, Senior Entomologist, Plant & Food says that thepsyllid research is multi-pronged with research organisations and the industry trying to work in together their combined resources to learn how to deal with the issue.

Nadine says that given the potential impact of this insect and its associated pathogen(s) on crop yields, immediate control options are required. Thirteen insecticides were selected for testing they were applied at recommended field rates as a spray (12 chemicals) or a seedling drench (1 chemical). She has some results on those tests but says further tests are required to confirm the efficacy under cropping conditions. In general pyrethroids and organophosphates gave good knockdown rates.

Producers of potatoes in New Zealand already use insecticides to control potato tuber moth and several species of virus transmitting aphids. She says insecticide resistance management strategies have been developed for these potato insects.

The arrival of psyllid threatens the use of IPM practices in potato, tomato and greenhouse crops. For greenhouse crops, there are no biological control agents, or IPM-compatible insecticides registered for control of psyllid.

For tomato and potato crops, management systems in place for avoiding resistance for key insect pests are threatened by a lack of registered insecticides for the control of psyllid.

Some of insecticide trial work has been done using psyllids nymphs obtained from Auckland. Nadine has published result of trials with insecticides. One of the problems is that the most effective insecticides in her results also kill the natural enemies of the psyllid therefore jeopardising any ongoing biological control.

In research south of Auckland theyve discovered that psyllid damage isnt appearing until December and that early crops were of good quality. A predator bug called Tamarixia has been imported from Mexico for evaluation initial indicators are that they may work well on spuds.

Nadine has sticky traps and cages on the Oakley property. She is also monitoring the plants. She says at this stage the damage isnt clear.

On-going research will be about monitoring and detection the psyllid.